Drug prescription in dentistry

•Maximising effectiveness •Minimising risk •Respecting patient choice, and•Minimising cost.

Example 1

You see a woman with a facial swelling due to a periapical abscess. She informs you that she developed acute breathing problems and a low blood pressure when given piperacillin injection.

Which antibiotic should you prescribe?

The patient has a history of immediate hypersensitivity reaction to piperacillin. Patients who are allergic to one penicillin will be allergic to all because the hypersensitivity is related to the basic penicillin structure. You should avoid prescribing amoxicillin for this patient. Metronidazole can be used.

The drug you choose to treat an oral condition should have minimal detrimental effects on the patient's other diseases and minimise the patient's susceptibility to adverse effects. To achieve this, you need to review the cautions and contra-indications of the drug you intend to prescribe.

Hepatic or renal disease may alter the metabolism or excretion of some drugs. Hepatic reserve and renal clearance reduce with age, and the elderly are particularly susceptible to the side-effects of drugs that are eliminated by these routes.

Select drug treatments that minimise the potential for drug accumulation, adverse drug reactions and exacerbation of pre-existing liver or renal disease .

Make appropriate drug dose adjustments for these patients .

Monitor patients appropriately if it is necessary to prescribe drugs whose response is altered by liver or renal disease.

the normal dose for herpes zoster should be given every eight hours if the creatinine clearance is 10-25 ml/minute. For this patient of average build and height, the eGFR can be used in place of creatinine clearance to make drug dose adjustments. This patient should receive aciclovir 800 mg every eight hours for seven days.

note

eGFR is estimated Glomerular Filtration Rate, usually based on serum Creatinine level.

NSAID may cause sodium and water retention and further deterioration in renal function in this patient. It is more appropriate to try paracetamol first. An NSAID should only be used, if essential, at the lowest effective dose and renal function should be monitored.

in severe liver disease the total daily dose of metronidazole should be reduced to one-third, and given once daily. This patient should receive 200 mg daily for three days.

Determine whether a mother's condition requires drug therapy.

Select drug treatments that minimise harm to the foetus, nursing infant and mother

Monitor the infant for potential side-effects of drugs used by the mother during pregnancy or breast-feeding.

if an NSAID is used regularly during the third trimester of pregnancy, it may cause closure of the foetal ductus arteriosus in utero and possibly pulmonary hypertension of the newborn. The onset of labour may be delayed and the duration of labour may be increased. Paracetamol is not known to be harmful and can be used.

fluconazole is effective for infection that has not responded to topical therapy. Although fluconazole presents in milk, the amount is probably too small to be harmful. Before prescribing the fluconazole, you should also consider the health status of the nursing infant, in this case a healthy baby.

The possible options for treatment include amoxicillin, doxycycline, or erythromycin.

Isotretinoin is a retinoid. There is a possible increased risk of benign intracranial hypertension when retinoids are given with tetracyclines. It is classified as a potentially hazardous interaction and concomitant use should be avoided.

Amoxicillin or erythromycin can be prescribed because itdoes not have an interaction between these antibiotics and retinoids.

the possible options for treatment include metronidazole or amoxicillin.

metronidazole may enhance the anticoagulant effect of warfarin and this is classified as a potentially hazardous interaction. Although studies have failed to demonstrate an interaction between warfarin and broad-spectrum penicillins such as amoxicillin, common experience in anticoagulant clinics is that the INR can be altered by these antibiotics.

Amoxicillin can be prescribed but you should arrange for the patient to be seen by the anticoagulant clinic earlier than scheduled. The patient should be advised to seek medical attention if persistent bleeding occurs.

When choosing a drug you should review the impact that any potential side-effect may have on a patient's quality of life. In other words, you need to assess the risks and benefits of prescribing a particular drug (see Example 11).

The side-effects for tetracyclines show that they can cause dysphagia and oesophageal irritation. Furthermore, the doxycycline, tetracycline, and oxytetracycline include counselling advice that recommends that they should be swallowed whole with plenty of fluid while sitting or standing. Metronidazole suspension is more appropriate for this patient.

The doses of some drugs vary according to indications – if no specific dose is given for a dental indication then the general dose can be used. The dose for children will vary according to their age or body-weight. You may need to adjust the dose of some drugs if their effects are altered by concomitant use with other drugs, or in patients with hepatic or renal impairment. Where a drug can be administered by more than one route you should ensure that you choose the right dose for the right route (see Example 12).

The general dose for doxycycline is200 mg on the first day then 100 mg daily. The lower dose of doxcycline does not have an antibacterial effect.

Select an antibiotic with a spectrum of activity that is appropriate for the infection. Regional guidelines and local patterns of resistance will influence your treatment .

Use adequate doses of an antibiotic . Avoid unduly prolonged courses of antibiotics.