Abstract. – The present work on drug-in- duced ototoxicity, tinnitus and vertigo repre- sents the update and revision of a previous guide to adverse drug reactions for italian physi- cians (2005). The panorama of drug-induced side effects causing ototoxicity or symptoms such as tinnitus or dizziness and vertigo has en- larged in recent years, thanks to a better knowl- edge and a more specific attention of pharma- ceutical firms and drug-control institutions. In daily clinical practice, there is a need for the family physician and the ENT specialist or audi- ologist (also in consideration of the possible medico-legal implications) to focus the attention on the possible risk of otological side effects. This would allow a clinical risk-benefit evalua- tion, weighing the possible clinical advantage in their field of competence against possible oto- logical side-effects. The list of active ingredients and drugs is subdivided in categories based on their audiological and otoneurological side-ef- fects, that have been signaled by the drug com- panies and/or ministerial notes. Drugs have also been subcategorized with regards to the field in which they are applied, the therapeutic indica- tions and the clinical behaviour. They have also been organized in alphabetical order, for an easi- er consultation. The guide above, even if initially conceived for being used in Italy, also presents a more general and international interest, expecially as for as the concepts of pharmacology and the features of the active ingredients are con- cerned. The guide is, therefore, useful as for as we are concerned to any physician, regardless of the country he/she operates in. Key Words: Pharmacovigilance, Side-effects, Ototoxicity, Tinni- tus, Vertigo. European Review for Medical and Pharmacological Sciences Pharmacological drugs inducing ototoxicity, vestibular symptoms and tinnitus: a reasoned and updated guide G. CIANFRONE 1 , D. PENTANGELO 1 , F. CIANFRONE 2 , F. MAZZEI 1 , R. TURCHETTA 1 , M.P. ORLANDO 1 , G. ALTISSIMI 1 1 Department of Otolaryngology, Audiology and Phoniatrics, “Umberto I” University Hospital, Sapienza University, Rome (Italy); 2 Institute of Otorhinolaryngology, School of Medicine, Catholic University of the Sacred Heart, Rome (Italy) Corresponding Author: Giancarlo Cianfrone, MD; e-mail: [email protected]601 Introduction The panorama of the pharmacological origin iatrogenic noxae able to induce either harmful ototoxic effects or just a symptomatology like tin- nitus or balance disturbances, without any harm- ful consequence, has widened in the last few years. The reason for this is the progress of scien- tific knowledge, the increased awareness of the pharmaceutical companies and of the institutions, which supervise pharmaceutical production. Only through continuous updating and experi- ence sharing it’s possible to offer patients the certainty of receiving the treatment that is appro- priate, safe and effective and based upon the most credited clinical studies. This approach is definitely challenging but necessary in order to attain positive effects towards the improvement of patient’s conditions and quality of life. In every day medical practice physicians, oto- laryngologists and audiologists, need to focus on the risks of otologic side effects, also from a le- gal point of view. It will then be beneficial to have a wider variety of drugs of the same family at hand, therefore, having a wider range of op- tions meeting the main therapeutic line. Physi- cians have to daily balance the drug between ef- fectiveness and safety; in any case the optimiza- tion of the pharmacological/therapeutic ratio has to be strictly related to the compromise between clinical advantages and undesired side effects. Today’s work on ototoxic, tinnitus and vertigo induced drugs is a revision and an update of what was previously published in 2005, regarding unde- sired side effects of drugs of the otoaudiologic field, which has had a positive result and has drawn inter- est from both general and specialized practitioners 1 . 2011; 15: 601-636
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Abstract. – The present work on drug-in-duced ototoxicity, tinnitus and vertigo repre-sents the update and revision of a previousguide to adverse drug reactions for italian physi-cians (2005). The panorama of drug-inducedside effects causing ototoxicity or symptomssuch as tinnitus or dizziness and vertigo has en-larged in recent years, thanks to a better knowl-edge and a more specific attention of pharma-ceutical firms and drug-control institutions. Indaily clinical practice, there is a need for thefamily physician and the ENT specialist or audi-ologist (also in consideration of the possiblemedico-legal implications) to focus the attentionon the possible risk of otological side effects.This would allow a clinical risk-benefit evalua-tion, weighing the possible clinical advantage intheir field of competence against possible oto-logical side-effects. The list of active ingredientsand drugs is subdivided in categories based ontheir audiological and otoneurological side-ef-fects, that have been signaled by the drug com-panies and/or ministerial notes. Drugs have alsobeen subcategorized with regards to the field inwhich they are applied, the therapeutic indica-tions and the clinical behaviour. They have alsobeen organized in alphabetical order, for an easi-er consultation.
The guide above, even if initially conceivedfor being used in Italy, also presents a moregeneral and international interest, expecially asfor as the concepts of pharmacology and thefeatures of the active ingredients are con-cerned.
The guide is, therefore, useful as for as weare concerned to any physician, regardless ofthe country he/she operates in.
European Review for Medical and Pharmacological Sciences
Pharmacological drugs inducing ototoxicity,vestibular symptoms and tinnitus: a reasoned and updated guide
G. CIANFRONE1, D. PENTANGELO1, F. CIANFRONE2, F. MAZZEI1,R. TURCHETTA1, M.P. ORLANDO1, G. ALTISSIMI1
1Department of Otolaryngology, Audiology and Phoniatrics, “Umberto I” University Hospital,Sapienza University, Rome (Italy); 2Institute of Otorhinolaryngology, School of Medicine, Catholic University of the Sacred Heart,Rome (Italy)
The panorama of the pharmacological originiatrogenic noxae able to induce either harmfulototoxic effects or just a symptomatology like tin-nitus or balance disturbances, without any harm-ful consequence, has widened in the last fewyears. The reason for this is the progress of scien-tific knowledge, the increased awareness of thepharmaceutical companies and of the institutions,which supervise pharmaceutical production.
Only through continuous updating and experi-ence sharing it’s possible to offer patients thecertainty of receiving the treatment that is appro-priate, safe and effective and based upon themost credited clinical studies. This approach isdefinitely challenging but necessary in order toattain positive effects towards the improvementof patient’s conditions and quality of life.
In every day medical practice physicians, oto-laryngologists and audiologists, need to focus onthe risks of otologic side effects, also from a le-gal point of view. It will then be beneficial tohave a wider variety of drugs of the same familyat hand, therefore, having a wider range of op-tions meeting the main therapeutic line. Physi-cians have to daily balance the drug between ef-fectiveness and safety; in any case the optimiza-tion of the pharmacological/therapeutic ratio hasto be strictly related to the compromise betweenclinical advantages and undesired side effects.
Today’s work on ototoxic, tinnitus and vertigoinduced drugs is a revision and an update of whatwas previously published in 2005, regarding unde-sired side effects of drugs of the otoaudiologic field,which has had a positive result and has drawn inter-est from both general and specialized practitioners1.
2011; 15: 601-636
602
In the specialised medical practice of otolaryn-gology and audiology there is the need to evalu-ate the patient from a pharmaceutical point ofview to assess the potential risks of otologic sideeffects. This will allow the evaluation of clinicaladvantages versus otologic adverse events. Theaim is to optimise the drug administration sched-ule in order to obtain a therapeutic improvementwhile sustaining the least number of side effectsin the otovestibular apparatus. Sometimes symp-tomatic or harmful effects do not show up imme-diately after the first treatment but after a certaintime, varying from subject to subject. This delaycould be explained by an increase in the organsvulnerability and/or a minimal asymptomaticevent after the first treatment and will later be re-vealed by the next dosage. In other instances sideeffects could be induced by following non-patho-genic non-iatrogenic noxae (trauma, noise, infec-tions, circulatory, metabolic or endocrynologicdisorders) or iatrogenic (oto-surgery).
Pharmacological ActionInfluencing Factors
Factors affecting the pharmacological actionare: the drug itself (dosage, chemical, physical orphysical/chemical properties), the combinationwith other drugs or substances (interaction andother types of interference), pharmaceuticalpreparation (which affects the bio-availability ofthe active principle) or other factors relating tothe patient using the drug and by the space/timecontext in which the drug is administered.
It is well known how the season, the climate,the altitude, the temperature etc. may interferewith the pharmacological action determiningsometimes a change from being curative to beingtoxic. Ultimately the patient is the factor thatmost affects the pharmacological action, it de-pends on the general physiological state of thesubject, on the pathological conditions involved,on his capability to metabolise and so eliminatethe drug, on his sensitivity, which could be high(up to the induction of hyper-sensitivity phenom-ena both idiosyncratic or allergic) or low. At lastfactors like gender, age, race, body weight andeven social condition and psychological profileare also important in determining or influencingthe pharmacological action2.
InteractionsAn additional consideration has to be given to
pharmaco-dynamic and pharmaco-kinetic ac-tions between different drugs used simultaneous-
ly. The current, sometimes marginal, knowledgeof drug behaviours make interactions a delicateissue.
The effects of a drug could be affected by thepresence of either of another drug or of food gen-erating an interaction that could be dangerouswhen causing an increase in toxicity or a de-crease in effectiveness. Food creates rare and lessimportant clinical interactions by effecting thespeed and the degree of absorption of a drug.Fortunately combinations of drugs to be avoidedare only a handful and many drugs with interac-tion issues can be administered simultaneouslyby taking proper precautions.
Pharmaco-dynamic interactions take placewhen the effects of a drug are interfered with bythe presence of another drug on the action site.They arise between drugs which share the sameor opposite therapeutic effects and that act uponthe same physiologic system i.e. sedatives thataffect brain and respiratory functions. On thecontrary, certain drugs could reduce the effective-ness of others because they compete for the samereceptors.
Pharmaco-kinetic interactions can take placeat the following levels:
Absorption: affecting bioavailability of a drugby altering the absorption coefficient or the to-tal quantity of the drug absorbed;
Distribution: the circulation of a drug can be inan inactive form, binded to proteins, or in anactive form, not binded; administration ofdrugs competing for the same proteic linkagemight cause an increase in the “free quota” ofthe drug and consequently its activity;
Metabolism: interactions can take place betweendrugs metabolized by the same enzymatic sys-tem, they can act as enzymatic inductors accel-erating the metabolism of the other drug andso reducing its effectiveness, or as enzymaticinhibitors slowing down the metabolism of theother drug creating accumulation and thus anincreased risk for dosage related side effects;
Elimination of the drug: interactions can causean alteration of both active tubular separationand glomerular filtration during renal clear-ance of certain drugs.
We can understand that the problem of druginteractions during co-administration is impor-tant and delicate. As an example, on “Medicinesfor Children”, the paediatric therapeutic formula-ry issued by the Royal College of Paediatricians
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
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remain in their system for a longer period of timecreating accumulation. The nervous system be-comes more sensitive with age and many com-mon drugs like opioid analgesics, benzodi-azepine, anti-psychotics, Parkinson’s diseasedrugs have to be used with caution. In a similarway other organs could be more reactive to cer-tain molecules i.e. non-steroidal anti-hyperten-sive or anti-inflammatory drugs. The reasonsabove are why elderly patients are more sensitiveto side affects and tend to accumulate massiveamounts of drugs in their system.
There is also a need to consider other factorslike self-medication, very common among the el-derly who often use drugs unnecessarily or don’tseek medical advice, either because of lack ofknowledge or just carelessness, and other age-re-lated factors like loss of memory, eyesight andmanual dexterity which can all interfere with aproper drug administration schedule.
Pharmaceutical Drugs:Pre-marketing Studies
Before a new medication is released on themarket and prescribed to people, it needs to beproved safe, active and effective and that the rela-tion between the risk of side effects and thera-peutic benefits is beneficial. The owner of themedication, normally the pharmaceutical compa-ny, is responsible for collecting all of this infor-mation. Developing a new medication normallytakes a long period of time, sometimes a fewyears, in pre-clinical laboratory studies on ani-mals and clinical studies on humans.
Agencies like the Food and Drugs Administra-tion (FDA) in the USA and the European Medi-cines Agency (EMEA) in the EU rule pharma-ceutical research. The Italian Medicines Agency(AIFA) was recently established in Italy. Studieson both animals and humans have to be submit-ted to these agencies in order to obtain approvalfor market release and for clinical use.
In 1970 the British Committee on the Safetyof Drugs (today called Committee on Safety ofMedicines) stated in its annual report4 “it iswell known that a medication that is effectiveinvolves a number of risks. Furthermore it isnot certain that all risks can be identified beforeits release to the public, not all trials on ani-mals and humans will reveal all the possibleside-effects of a medication. This data will onlybe available after a medication has been admin-istered to a large number of patients over a longperiod of time”.
and Child Health, which is also included in the“Children Drugs User Guide” published by theItalian Department of Health3, the combinationof an aminoglycoside like amikacin with vanco-cymin, ciclosporin, cisplatin, furosemide or am-photericin might increase the risk for ototoxicityand nephrotoxicity, but even the association ofamikacin with non-ototoxic drugs likecephalosporin, according to the source, might in-crease the risk for ototoxicity.
To this day it is not possible to anticipate theotologic effects of a single drug, of a combina-tion of drugs, or of drugs combined with non-ia-trogenic events such as exposition to noise. Itlooks like predisposition or genetic vulnerabilitymight play an important role in such instances.
Drug AccumulationDrug accumulation can take place when the
drug is reintroduced too early, that being beforethe equivalent quantity of the previous dose hasbeen eliminated causing an increase in plasmaconcentration leading to possible toxic phenome-na due to accumulation. Accumulation is thus in-versely proportional to the percentage of thedosage eliminated between administrations.
Drug accumulation can also take place be-cause of a reduced elimination of the drug (i.e.patients with a kidney failure condition) or be-cause of a pathologic state which slows down thehepatic and extra-hepatic metabolic processes.Co-administration of drugs can also cause accu-mulation as mentioned above because of eitherpharmaco-dynamic or pharmaco-kinetic interfer-ences. Finally, we can observe accumulationwhen using drugs with a slow elimination rateand/or a longer half-life, either because of theslowness in reaching equilibrium or in the de-crease of plasma concentration once the therapyis suspended2.
In our otoaudiologic field we experience thisproblem because of the age group our patientsfall into and because of the often chronic audio-vestibular conditions we treat. As a matter of factwe often treat older patients suffering from otherconditions and following other pharmacologicaltreatments, especially the ones with chronicpathologies.
Elderly patients must use extreme caution us-ing drugs because they often have to use a num-ber of different drugs, increasing the risk of inter-actions and adverse reactions. They tend to havea slower metabolism so food and drugs are elimi-nated at a slower rate; consequently drugs tend to
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It has recently been determined5 that 51 per-cent of the approved drugs show severe adversereactions undetected before approval.
Adverse Drug Reactions (ADRs) can thus beidentified either before or after the experimentalphases that lead to final market release. Pre-mar-keting clinical trials seldom identify or determinethe frequency of severe adverse reactions. Theinformation sheet of the medication states the in-formation available at the time of approval. Theresult of this process is that once the medicationis released on the market both doctor and patientare often unaware that they are continuing to testthe drug even to a much greater level than the ex-periments previously done.
Drug Safety MonitoringDrug safety monitoring is the process of evalu-
ating the undesirable side effects potentially re-lated to the pharmacologic treatment6.
Drug safety monitoring has four main objec-tives7:
• To detect new ADRs as soon as possible.• To improve and distribute information regard-
ing known or suspected ADRs.• To evaluate the advantages of a medication
versus another or over other types of therapy.• To provide information in order to improve
medical practices.
Most common ADRs are severe and related tonew drugs released on the market8.
The main effects observed8,9 are related to thegastro enteric system (31-35%), central nervoussystem (15-20%), and skin (10-11%).
The most common drugs8,9 causing ADRs arethe cardiovascular ones.
ADR Classification and DefinitionAdverse reactions to medication have different
forms, are heterogeneous and often unexpectedand unpredicted10.
They can be classified, as per the Inman11 pro-posal, in three types A, B and C depending ontheir characteristics, on the difficulty of identifi-cation and on the most effective methods to iden-tify them12.
ADRs of the A type are the most commonones and are defined by the World Health Organ-isation (WHO) as side effects. They tend to befairly common and dosage-related. They can be
caused by an excessive pharmacological actionor by a secondary pharmacological action of themedication or even by pharmaco-kinetic interfer-ences. Even though their incidence and morbidityis high they seldom cause a threat to the patient’slife. They can normally be detected before mar-ket release and can be replicated in the laborato-ry. Nevertheless, their identification can be morecomplex under certain conditions like: when onlya minority of the subjects show a reaction, orwhen there isn’t a direct relation with dosage, orwhen the reaction is common or not important,or when it is difficult to obtain on animals, orwhen they coincide with other causes (e.g.cephalalgia). The mechanism is unclear.
ADRs of the B type are often of an allergic,immunologic or idiosyncratic nature and takeplace in a minority of patients (less than 1 per1000) and they are normally unexpected and un-predictable. They are generally severe and havelittle or no relation to dosage, they don’t repre-sent an extension of the pharmacological reactionand are difficult to identify for a number of rea-sons. They tend to affect certain organs: liver,hematopoietic system and skin. The time framebetween the medication intake and the appear-ance of the symptoms and the low retrospectivefrequency of the symptoms lead to consider themedication responsible for the reaction. Exceptfor conditions of immediate hypersensitivity(anaphylaxis) these reactions take place normallyafter five days from beginning of the treatment(time in which cells become hyper-sensitive tothe drug) and there is no upper limit even thoughmost reactions take place within the first twelveweeks.
Patients often have predispositions that are notalways evident. Certain reactions have an im-munological base, others recognise a metabolicgenetic error or an acquired deficiency to a cer-tain enzyme, causing an abnormal metabolicpathway or an accumulation of toxic metabolites.
Regarding type C ADRs we need to say that,especially when medication is used over manyyears or for the rest of one’s life, they can inducenew medical conditions or change the incidenceof the existing ones. Examples of this risk can beidentified with the possible incidence of breastcancer or thromboembolic complications in-duced by birth control pills. These events can besevere and fairly common and can significantlyaffect public health. The late onset of a diseasemakes it difficult to identify it as a pharmaco-re-lated pathology.
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
ADRs regarding our field can definitely be at-tributed to the first group, type A. They are infact undesired effects, common type, dosage re-lated and non-life threatening.
Specifically, ototoxicity is regarded as an ad-verse reaction affecting the inner ear leading toalterations either transitory or permanent of theauditory or vestibular functions. We believe thatresearch over the last decades on the suspecteddrugs action mechanisms still has a long way togo. It is then very important to gain a deeperknowledge of these action mechanisms in the fu-ture in order to let the patient benefit from themost effective means of prevention derived fromtherapy13. Complete or partial loss of the auditoryor vestibular functions can have a severe impacton quality of life and socioeconomic status14.
Incidence and Frequency of ADRsEvaluating the incidence and frequency of
ADRs is not simple because the comparison be-tween published studies is not always possibledue to the differences in exposition to the specif-ic drug of different populations or the differencesin the ADR detection methods. In fact, somestudies only account for adverse reactions whileothers also account for overdose or because cer-tain studies consider only the manifested clinicalconditions and others consider laboratory para-meter alterations as well15-29.
ADRs are responsible for 3-7% of all hospital-isation cases. The U.S. prospective studiesshowed ADRs in 10-20% of all hospitalisations,in which 10-20% were severe. The incidence ofdeath caused by ADRs is unknown, they suggest-ed rates between 0.5 and 0.9% but they includedpatients with complex and severe patholo-gies20,21,23-29.
Incidence and severity of ADRs can be influ-enced by many factors related to the patient (age,gender, present diseases, genetic factors and geo-graphic factors) and to the medication (type ofdrug, route of administration, therapy duration,dosage and bio-availability). Incidence andseverity are probably higher in older people. It isunclear how prescription errors and patients lackof compliance affect ADR incidence.
Pharmaceutical producers declare the frequen-cy of side effect occurrences on certain medica-tions. Such information is reported through agrading system going from < 0,01% (very rare)to >=10% (very common).
Nowadays, drug safety surveillance institu-tions tend to persuade the pharmaceutical indus-
try to improve the utilisation of this grading scaleas a main element in the general management ofthe pharmacological therapy.
Because of this, the data we now hold willsoon be updated and become more detailed.
ADR CostsAdverse reactions do not only affect people’s
health but have a great economic impact as well. The research on ADR costs has only recently
started, following the Institutions request to re-duce public health costs.
Works published in the last years have tried toquantify costs and research had to be based onfactors like the increase in incidence on medicalexams, the number of hospitalisations, the num-ber of additional therapies needed and the length-ening of hospitalisation periods, etc18,24,27,30,31.
OtotoxicityLet’s now make a few considerations on oto-
toxicity without expecting them to be exhaustiveon such a complex and articulated topic that inmany ways is still unknown.
Ototoxicity is defined by the toxic capacity ofcertain drugs or toxins relative to the inner earstructures (particularly to the cochlea and thevestibular cells) or the acoustic nerve. Ototoxicdrugs can act on the cochlea, the vestibular sys-tem or both32-34.
Toxic damage is often shown by symptomslike tinnitus, vertigo, hyperacusis and deafness.Hearing impairment, tinnitus and vertigo are themost important medical conditions of the innerear due to a drug-induced damage. The onset ofthese symptoms can be simultaneous or singular,they can develop rapidly or gradually and can bereversible or not. The ototoxic action can lead, inthe most severe cases, to remarkable functionalreductions of the hearing capability or completedeafness32-33-34.
A possible genetic predisposition is assumedto be facilitating the ototoxic action35-40. There isa remarkable difference in ototoxic sensitivityamong different animal species. This informationhas to be carefully taken into consideration whentranslating research from animal models to hu-mans41. As an example, guinea pigs and humansshare the same ototoxic dosage of cisplatin,while guinea pigs showed much more tolerant togentamicin than humans41. These drugs can bedangerous for both the auditory and the vestibu-lar parts and to a greater extent to the organ ofCorti (cochleotoxic).
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Pharmacological drugs inducing ototoxicity, vestibular symptoms and tinnitus
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Because almost every ototoxic drug is elimi-nated through the kidneys the reaching of levelsof toxicity is facilitated by renal failure. Whenev-er the renal function is altered ototoxic drugdosages, eliminated through the kidneys, have tobe corrected so that hematic levels remain withintherapeutic limits. Serum levels of the drug (highor minimal) should be checked in order to get thecorrect therapeutical levels. As a matter of facteven with subjective changes of sensitivity to thedrug, hearing is usually preserved if hematic lev-els remain within the suggested limits.
Ototoxic drugs shouldn’t be prescribed fortopical medications in the event of an eardrumperforation since the inner ear fluids, through thesecondary eardrum of the oval window, could ab-sorb the drug. This practice is quite debated but itis fairly common to find a clinical usage ofeardrops containing antibiotics or other ototoxicdrugs in chronic otitis even in the presence of aperforated eardrum42,43.
Ototoxic antibiotics should not be used onpregnant women. Hearing impaired and elderlypeople should not be given ototoxic medica-tions if a non-toxic alternative is available. Anevaluation of a pre-existing condition of hear-ing impairment should be done before prescrib-ing ototoxic antibiotics. Hearing ability has tobe monitored through audiometric examsthroughout the therapy. According to the Amer-ican Speech-Language-Hearing Association(ASHA) a tonal audiometric exam should becarried out 24 hours after the beginning of thetherapy and every two or three days for the restof the therapy.
The high frequency analysis would supplyeven more precise and reliable results44-47.
The reason for this monitoring is to obtain aphysio-pathological description of the ototoxicagents derived damages, outlining the clinical as-pects of the damages to the cochlea and to thevestibular receptors, keeping track of the changesover time48. High frequencies are generally moresensitive to the treatment and high-pitched tinni-tus or vertigo can take place, but they are not al-ways reliable signs to pre-alert.
Transient evoked otoacoustic emission (TEOAE)and distortion product otoacoustic emission(DPOAE) tests are today considered gold-standardexams in ototoxicity control, allowing assessmentof cochlea function at high frequencies in just afew minutes. Clinical studies confirm the strict re-lationship between otoemission and ototoxicity.Otoemissions as a matter of fact allow the detec-
tion of levels of ototoxicity from the beginning ofthe treatment, sometimes even before any audio-metric deficit is detected.
The simultaneous exposition to noise is aworsening factor due to the increased release offree radicals.
Cochlear dysfunction can span from a lightincrease of the hearing threshold, only de-tectable through audiometry, to complete deaf-ness. Hearing loss can take place along with ei-ther temporary or permanent tinnitus. Clinical-ly cochlear damage appears sooner thanvestibular damage that could even be severe be-fore the onset of vertigo. The actual extent ofvestibular damage is hard to assess, vestibulardamages can go undetected especially if thedamage development is slow and progressive(in most cases bilateral)47.
Early detection of toxicity enables the adjust-ment of dosage, the suspension of therapy andthe change of medication. In many instancesdamage evolves over time: in a group of paedi-atric patients, damage of 11% at the beginning oftreatment increased to 44% two years later49.
Ototoxicity is considered a pharmacologicaladverse reaction affecting the inner ear, charac-terized by cochlear or vestibular dysfunction.
The Council for International Organisations ofMedical Sciences (CMIOS), in order to standard-ise the terminology regarding medication safety,has produced a list of definitions of ADRs andthe relative proper procedures. The developmentsof deafness, tinnitus or vertigo associated withpharmacological treatment are minimum require-ments to refer to ADRs.
While an ototoxic damage can be determinedby a routine anamnesis, ototoxic loss of hearingcan only be determined by comparison of audio-grams from before and after the treatment. To di-agnose a pharmacologically caused deafness it isnecessary to verify through audiometry an in-crease of the equal loudness contour by 15dBover one or more frequencies. In any case it ishard to mention pharmacological etiology with-out having audiograms from before and after thetherapy.
Legal debates over iatrogenic damage due toototoxicity are very rare and only attaining se-vere cases that led to communication disorders(severe hearing loss over many frequencies)48.
Drugs ototoxicity is a very delicate issue be-cause many pathologies are treated through theuse of drugs that are potentially harmful to theinner ear.
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
There is evidence about inner ear tissues be-ing immunologically, biochemically and func-tionally related to kidney tissues. It seems thatmedications affecting sodium and potassiumtransport alter ionic homeostasis of the inner earcausing functional problems like hearing loss,tinnitus and vertigo44. Renal pharmacologicaladverse reactions have been studied in the effortof finding predictive signs of possible ADRs re-lated to the inner ear or to the labyrinth andabout medication class’s influence upon ionictransportation. Resulting data showed that renalADRs couldn’t be considered markers of phar-macologically induced disturbances to the innerear or labyrinth. Nevertheless, the ability ofthese drugs to influence the ion transport systemand the ion channels and so influencing the earand kidney ionic homeostasis could be a pre-dicting factor for a possible pharmaceutical re-lated ototoxicity44.
No dosage appears to be safe in amino-glyco-side therapies no matter what the administrationroute is (parenteral, intratympanic, per os, in-trathecal). Certain studies show how a daily sin-gle administration of amino-glycosides is as ef-fective as a set of daily injections, thus a smallerquantity of the medication leads to the same re-sults50.
In any case monitoring the cochleo-vestibularfunction is always very important. Genetic pre-disposition has been suspected for severe deaf-ness onsets just after a few amino-glycoside in-jections. As far as medication interactions areconcerned, specifically between amino-glyco-sides and other drugs, the issue has been coveredin the preceding paragraph (see page 602, Inter-actions).
Individual susceptibility and organ vulnerabili-ty are debated issues because of their relevanceand criticality and often related to genetic char-acteristics. Several studies today reveal how cer-tain mitochondrial chromosome mutations canrepresent one of the genetic factors for hypersen-sitivity, vulnerability and predisposition towardsamino-glycosides51-53.
A hereditary non-syndromic familiar form as-sociated with the A1555G mutation (substitutionof a guanine with an adenine) located on the mi-tochondrial RNA12S has been discovered51. TheA1555G mutation is very common in Spain,reaching 25%45. Due to the high incidence in thiscountry, detection of the genetic mutation is car-ried out systematically in order to avoid amino-glycoside ototoxicity51,54-57.
Bacteric ribosomal RNA is the amino-glyco-sides target and the mutated human form A1555Gis very similar to the bacteric one, it binds abnor-mally to the amino-glycoside explaining the rea-son for deafness even at low dosages of the drug.Some authors report that 17% of the subjects in-terested by amino-glycoside ototoxic effects havesuch mutation51-53,58.
A recent study on the frequency of mitochondricmutation over a selected Japanese populationspecifically selected because had experienced post-streptomycin tinnitus has shown the possibility thata new and rare mutation, C1556T, could appearalong with the A1555G as a hearing loss risk factor,specifically as a tinnitus-generating factor. It mustbe noted that according to the available literaturethe A1555G mutation doesn’t create any vulnera-bility of the vestibular apparatus even though thechromosomal mutation is present in all mitochon-dria of every tissue. The C1494T is another 12S ri-bosomal RNA mutation that can cause even if to alesser degree amino-glycoside susceptibility59.
We have seen that the way cisplatin causesototoxicity varies significantly from subject tosubject and that it is partially related to the genet-ic differences of the subjects39.
Identifying genetic variations and so predict-ing the severity of ototoxic effects would be animportant step towards a better-addressed use ofcisplatin39.
Guide Presentation
This work on ototoxic, tinnitus and vertigo-generating medications is, an update and a revi-sion of the previous guide published in 2005, re-garding collateral and undesired effects of med-ications in the oto-audiologic field1. We have ad-justed the Italian pharmacological context, re-garding active principles, to the international An-glo-Saxon one, intentionally omitting in this re-view commercial products as they pertain to indi-vidual country contexts.
This guide should be a practical, comprehen-sive list of drugs (actually of the active principlesof the drugs) used in this country and yet knownand used abroad, which can induce otologic andotoneurologic side effects, such as:
1. Ototoxicity, as a neurosensorial hearing dam-age also including the possible associatedlabirintine vertigo symptomatology and/or thepossible onset of tinnitus;
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2. The onset of tinnitus only, with no docu-mentable hearing damage;
3. The vertigo generating action only, withoutany evident toxic action on the hearing appara-tus.
These side effects have a different weight froma practical point of view. In fact, while adverse re-actions related to ototoxicity can justify higherlevels of alert based on the ADR scale accordingto Hartwig et al60, side effect-generating tinnitusand vertigo hold a certainly lower level of gravity.
Data contained in publication is a complexelaboration of the information found on the“Guida all’uso dei Farmaci” (2008), based on theBritish National Formulary (BNF), by the ItalianDepartment of Health and by the Italian Medi-cines Agency (AIFA).
The Guide mentioned is a translation and anadaptation to the Italian context of the BritishNational Formulary, a prestigious publicationcreated in Great Britain many years ago andmade possible thanks to a scientific collaborationagreement between AIFA, the British MedicalAssociation and the Royal Pharmaceutical Soci-ety of Great Britain.
The Drugs User’s Guide is an easy to accessmanual, where the most relevant information re-garding the active principals of the drugs on ourmarket are gathered. It gives reference to theconditions for which they are suggested andvaluable indications for prescriptions to cate-gories of patients particularly subject to the riskof undesired reactions like elderly people, chil-dren and subjects with severe chronic conditionswho require co-administration of more drugs.
For this reason we believe it to be a usefulcontribution to professionals in this field.
Work Plan and Hints forDirectory Consultation
In this work the list of the pharmacological ac-tive principles is divided into sub-categories basedon the type of audiologic and otoneurologic sideeffects (hearing losses and disturbances, tinnitus,balance disorders and vertigo) reported by thepharmaceutical companies and/or by the HealthDepartment directives (the type of side effect is in-dicated in our lists with a number from 1 to 4).
Whenever possible we kept in considerationthe classification of drugs based on the apparatusthey attain to, the therapeutic indications and thepharmaco-clinical actions and we made alphabet-ical lists for easy reference.
More specifically these are the various typesof side effects listed and numbered:
1. Drugs with the explicit indication, by the phar-maceutical company and/or the Health Depart-ment, of “potentially otologically harmful”,generally indicated as ototoxicity (ototoxicdrugs); ototoxicity is meant as a neurosensori-al hearing damage (going from light hearingimpairment to deafness) and may include boththe possible associated symptomatology oflabyrinthical alteration vertigo and the possi-ble generation of tinnitus;
2. Drugs with the explicit indication, by the phar-maceutical company and/or the Health Depart-ment, as potentially tinnitus-generating, gener-ally called tinnitus, hissing ear, or acouphene(drugs openly declared as tinnitus generating);a potential tinnitus risk is reported for thesedrugs and there is no mention of ototoxicity;
3. Drugs with the explicit indication, by the phar-maceutical company and/or the Health Depart-ment, as potentially vertigo-generating drugs,generally called vertigo or dizziness (drugs open-ly declared as vertigo generating). Information ofpotential vertigo associated with the drug is re-ported while there is no mention of ototoxicity;
4. Drugs with possible audiologic effects, indi-cated as “hearing disturbances” (drugs withaspecific otologic side effects), it is advisableto have a conservative approach to these drugsand to evaluate in each case the possible inten-sity and type of adverse reaction.
Certain drugs can clearly be found in morethan one sub-category as they can lead to differ-ent ENT interests.
In order to provide an easier and better refer-ence, active principles in this book have beengrouped and listed in different ways:
Index A: general index, where we find the activeprinciples sorted mainly in reference to the ap-paratus they act upon, to the generic indicationsand to the pharmaco-clinical action and with areference to the relevant side effect, using thegrading scale 1 to 4 mentioned above. We liter-ally reproduced the “Guida all’uso dei Farmaci”(2008) layout to facilitate consultation.
Sub-indexes A1-A2-A3-A4: the pharmacologicalactive principles have been divided into fourside affect categories while maintaining thesame order of index A, by apparatuses, clinicalindications and pharmaco-clinical actions.
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
Index B: in this index the active principles arelisted in alphabetical order, each with a numer-ical reference to the relevant type of side ef-fect. Whenever possible according to dataavailable to us, believing it to be very useful,we indicated the side effect frequency for eachdrug using a grading scale from a to e goingfrom “very common” to “very rare”.
Pharmaceutical company indications aboutside effect frequency are normally expressed asfollows:
a Very common (≥ 10%)b Common (≥ 1% e < 10%)c Uncommon (≥ 0,1% e <1%)d Rare ( ≥ 0,01% e < 0,1%)e Very rare (< 0,01%)f Unknown, because available data is insuffi-
cient
It must be said that this grading is sometimesnot published or known by the manufacturers sowe haven’t assigned a grading letter to drugswith missing data.
Final Considerations andBehavioural Strategies forPractitioners
Based upon what was said so far, the suggest-ed behaviour for General Practitioners or forENT/Audiology specialists, whenever theyshould encounter problems connected to poten-tially risky pharmacological treatments, cannotbe as univocal, peremptory and directional.
As we mentioned in the foreword, the practi-tioner must always have the objective of findingthe right balance between effectiveness and safe-ty keeping in mind that pharmacological pro-gramming optimisation also means obtaining areasonable compromise between clinical advan-tages and risks related to adverse or undesiredside effects.
For this reason it is impossible to generalisethe strategies a practitioner has to follow. Insteadevery patient needs to be studied transversallyand observed longitudinally in an absolutelyelastic and individualistic way.
In each case the coexistence of additional riskfactors like old age, kidney conditions, dysmeta-bolic conditions, environmentally-related condi-tions of exposition to noise, genetic or familiar
predisposition to auditory pathologies or the co-existence of non-iatrogenic neuro-sensorial audi-ologic pathologies are all elements which couldinterfere with iatrogenic factors increasing therisk for ADRs.
The following suggestions may be given:
1. During anamnesis the pharmaco-therapeuticprofile of the patient accurately mark, previ-ous, current and scheduled intakes of drugswith potential risk of ADR, making note of themolecule, the commercial name, the posology,length of treatment and type of ADR and otherpossible additional and collateral factors ofrisk.
2. When dealing with a life-saving treatment or atreatment that cannot be stopped and/or is a re-sult of a long series of therapeutic trials, it isimproper to operate or to advise the patient’sdoctor for any changes of the therapeutic pro-file, generating unnecessary fears in the pa-tient. This is valid if we face an ototoxic drugtreatment or, even more, if we deal only withtinnitus and/or vertigo inducing drugs.We have to be reassuring with the patient andwarn him (in line with the current prescrip-tions of the law and with the professional ad-vises on using proper care about the patient’sconsent, when the treatment involves the useof ototoxic drugs) that possible disturbancescould be a normal consequence of the impor-tant treatment the patient is undergoing. Thepatient must also be informed that the distur-bances will be strictly monitored and that willbe softened by cell protecting treatmentsand/or small dosage adjustments.This soft, minimizing yet directional approachcould reveal very useful with patients showingtinnitus as a central symptom, whose psycho-logical involvement is well known to be fre-quent and penetrating.
3. The doctor’s behaviour towards patients whosepathologies are less severe and where medica-tion can be modified on both posology andtype, is definitely different. In such cases, ifusing ototoxic drugs, it is possible to act be-fore irreversible alterations take place, by talk-ing to the patient’s doctor and trying to co-manage the case by small therapeutic adjust-ments or more radical changes of the pharma-cological profile. When dealing with non oto-toxic tinnitus and or vertigo inducing drugsand in presence of a symptomatology, and therelationship the drug intake and the sympto-
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General index, where we find the active principlessorted mainly in reference to the apparatus they actupon, to the generic indications and to the pharmaco-clinical action and with a reference to the relevant sideeffect, using the grading scale 1 to 4 mentioned above:
1. Ototoxic drugs (ototoxicity may include both thepossible associated symptomatology of labyrinthi-cal alteration vertigo and the possible generation oftinnitus);
2. Drugs tinnitus-generating (there is no mention ofototoxicity);
3. Drugs vertigo-generating (there is no mention ofototoxicity);
4. Drugs with possible audiologic effects, indicated as“hearing disturbances” (drugs with aspecific otologicside effects).
Gastrointestinal System
Antispasmotic and other drugs used for intestinalmotility disorders• Antimuscarinic
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
ed, identifying subjects with risk of genetic pre-disposition and reducing self-medication in-stances along with a proper policy on the pa-tient’s drug use education will certainly helpnarrowing the number of ototoxicity cases.The Specialist is ultimately responsible for di-agnosis, medical care, giving advise, preven-tion and rehabilitation when dealing with theeffects of medications on the inner ear.
Conclusions
This work represents the update and the revi-sion of the previous guide on the unwanted sideeffects in the oto-audiological field. We believe ithas a larger international value and is to be con-sidered useful to any physician regardless of thecountry he/she operates in.
The risk of drug side-effects has become aburning issue, therefore, in daily clinical practice,doctors need to focus in that direction also inconsideration of the possible medical-legal impli-cations.
It will be useful and necessary to periodicallyupdate the data of the guide on the basis of thenew acquisitions about drugs. Obviously, in thepharmacological scene of each country, theremight be some drugs which are not included inthe above mentioned list or, on the contrary,some of the drugs listed here might not be in-cluded in those used in some countries.
The general interest of this document survives,as it may provide a pratical and useful guide forphysicians in their daily professional activity.
matology being unclear, it is possible with adechallenge/rechallenge strategy either partialor total depending on the case.Since harmful consequences for the auditorysystem cannot be predictable when using non-ototoxic drugs, there is wider flexibility re-garding the medical and legal information tobe given to the patient.
4. While managing different strategies it is advis-able to keep in consideration the concept offrequency (very common-very rare) of side ef-fects, at least for those drugs for which data isavailable; such element, which we classifiedwith the “a, b, c, d, e” codes, might reveal use-ful and sometimes determinant when choosingthe strategic behaviour to be adopted by theENT/Audiology Specialist
5. With the current knowledge to this date, it isimpossible to advise the patient’s doctor andthe specialist on behavioural strategies whendealing with drugs of category 4 (“hearing dis-turbances”) because the data available is verylimited on frequency and none on the specifictype of side effect.In such instances, especially with drugs withADR’s rated “common” or “very common”,the only advise that could be given is to becautious.We can finally say that a reasonable use of thedrug, including the early identification of theminimum effective dose, is certainly the bestway to reduce ototoxicity incidence.A better diffusion of the monitoring techniqueswould be useful even though they are still quiteunknown today and rarely requested. Althoughototoxic phenomena incidence is underestimat-
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Pharmacological drugs inducing ototoxicity, vestibular symptoms and tinnitus
Acne and rosacea• Anti acne preparations (oral route)
– Oral anti acne antibioticsErythromycinMinocycline
Anti infective skin preparations• Anti bacterial preparations
– Topical anti bacterial preparations (if you have totreat a large area of skin ototoxicity may be a riskassociated with aminoglycosides and polymyxin use)
Neomycin sulphate Polymyxin
Sub-index A2
Drugs Tinnitus-Generating
(There is no mention of ototoxicity).
Gastrointestinal System
Chronic intestinal disorders• Aminosalicylates
– Sulfasalazine
Cardiovascular System
Diuretics• Potassium-sparing and other diuretics
– Amiloride and hydrochlorothiazideAnti-arrhythmics• Supraventricular and ventricular arrhythmias
– Flecainide acetate Beta blockers• Timolol maleate Hypertension and heart failure• Drugs used for regulate renin-angiotensin system
• Drugs modifying the rheumatic diseases course – Cytokines inhibitors
Sulfasalazine Drugs used in neuromuscolar diseases• Skeletal muscle relaxants
– Limbs night crampsQuinine
Eye Medicaments
Antinfective eye preparations• Antibacterial
– Ciprofloxacin Glaucoma treatment• Beta blockers
– Timolol maleate
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
Diagnostic and perioperative preparations,photodynamic treatment• Perioperative ocular drugs
– Diclofenac sodium – Flurbiprofen sodium
Ear, Nose and Oropharynx
Anti-inflammatory steroids and associated antimicrobial• Ciprofloxacin + hydrocortisoneDrugs used for oropharynx• Drugs used for oral ulceration and inflammation
– Flurbiprofen
Skin
Acne and rosacea• Anti acne preparations (oral route)
– Oral anti acne antibioticsDoxycycline
Protective substances against uv radiations• Photodamage
– Diclofenac sodium
Sub-index A3
Drugs vertigo-generating
(There is no mention of ototoxicity).
Gastrointestinal System
Antispasmotic and other drugs used forintestinal motility disorders• Antimuscarinic
• Other antidepressants– Duloxetine – Mirtazapine – Reboxetine – Venlafaxina
Central nervous system stimulants and drugs used forattention deficit disorders and hyperactivity• Atomoxetine • Metilphenidate hydrochloride • Modafinil Drugs used in nausea and vertigo• Serotonin antagonists (5-ht3 receptor
– Levonorgestrel Progestin contraceptives• Progestin contraceptives (oral route)Drugs used for genito-urinary disorders• Drugs used for urinary retention
• Drugs used in malignant hyperthermia– Dantrolene sodium
Local anesthesia• Lidocaine
– Lidocaine hydrochloride
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Pharmacological drugs inducing ototoxicity, vestibular symptoms and tinnitus
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
Drugs altering immune system response• Corticosteroids and other immunosuppressors
– TacrolimusSex hormones and hormone antagonists in tumors• Hormone antagonists
– Prostate cancer and gonadotropin releasinghormone agonistBuserelin
Blood and Nutrition
Anemia and other hematic disorders• Drugs used in hypoplastic and hemolytic anemias
and in anemia in kidney diseases– Iron-chelating agents
Deferoxamine mesylate
Muscle Skeletal System
Drugs used in neuromuscolar diseases• Skeletal muscle relaxants
– Limbs night crampsQuinine
Eye Medicaments
Antinfective eye preparations• Antibacterial
– Ciprofloxacin– Levofloxacin
Glaucoma treatment• Carbonic anhydrase inhibitors and systemic drugs
– Acetazolamide
Ear, Nose and Oropharynx
Anti-inflammatory steroids and associated antimicrobial• Ciprofloxacin + hydrocortisone
Skin
Acne and rosacea• Topical anti acne preparations
– Topical retinoids and anti acne preparationsTretinoin
Anti acne preparations (oral route)• Oral retinoid used for acne• Isotretinoin
Sub-Index A4
Drugs with possible audiologic effects, indicated as“hearing disturbances” (drugs with aspecific otologicside effects), it is advisable to have a conservative ap-proach to these drugs and to evaluate in each case thepossible intensity and type of adverse reaction.
Central Nervous System
Hypnotic and anxiolytic drugs• Hypnotics
– Zaleplon, zolpidem e zopicloneZaleplonZolpidem tartrate
Pharmacological drugs inducing ototoxicity, vestibular symptoms and tinnitus
In this index the active principles are listed in al-phabetical order, each with a numerical reference tothe relevant type of side effect. Whenever possibleaccording to data available to us, believing it to be
very useful, we indicated the side effect frequencyfor each drug using a grading scale from a to e go-ing from “very common” to “very rare” (see page609).
Protein Conjugate) Hepatitis B Vaccine Recombinant
268 Halcinonide + Salicylic Acid 1269 Hepatitis A Inactivated & 3d
Hepatitis B (Recombinant) Vaccine 270 Hepatitis B Vaccine (Rdna) 3d271 Homatropine Bromhydrate 3272 Human Coagulation Factor IX 3c273 Human Coagulation Factor VIII 3274 Human Cytomegalovirus 3
G. Cianfrone, D. Pentangelo, F. Cianfrone, F. Mazzei, R. Turchetta, M.P. Orlando, G. Altissimi
––––––––––––––––––––Acknowledgements
This work has been supported by A.I.R.S. Onlus, theItalian Association for Research on Deafness. We wishto thank the Italian Medicines Agency (AIFA) for theircollaboration and bibliography support.
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