Drug interactions program for medical doctors, pharmacists and other health care proffesionals
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Drug interactions program for medical doctors,
pharmacists and other health care proffesionals
PharmDr. Josef SuchoparMUDr. Michal Prokes
INFOPHARM a.s., Prague Czech Republic
Drug interactions: Are they really important? • Metaanalysis of
39 prospective clinical trials has proved:
• Adverse Drug Reactions are 4th most frequent cause of death
• Lazarou et al: JAMA 1998
• Analysis of USA National Drug Register has proved:
• The cause of 2/3 of ADRs are drug interactions
• Phillips et al: JAMA 2001
Different kinds of drug interactions
PHARMACOKINETICDrug interactions:
PHARMACODYNAMIC
• Interaction drug - drug • Interaction drug - alcohol• Interaction drug - foods (and soft drinks)• Interaction drug – food supplements
All these kinds are divided into:
Drug interactions: – clinically relevant– not clinically relevant
Drug absorptio
n
Drug excretion
Drug metabolism
(biotransformation)
CYP3A4, CYP2D6, CYP2C9…
Pharmacokinetic drug interactions
Drug displacemen
t (protein-binding)
Transport of the drug inside the
body
Example: Changes of biological availability of midazolam caused by
coincident medication
-96% -94% -93%
-53%-100%
-50%
0%
50%
100%
150%
200%
250%
300%
350%
cim
etid
in
dilth
iaze
m
eryt
hro
myc
in
clar
ithro
myc
in
keto
conaz
ole
itra
conaz
ole
fluco
naz
ole
gra
pef
ruit
juic
e
rifa
mpic
ine
carb
amaz
epin
e
phen
ytoin
e
St
John´s
wort
Inhibitors of CYP3A4 increase bioavailability of midazolam, inducers of CYP3A4 lessen it.
Pharmacodynamic drug interaction
• Opposing or antagonistic interaction:– Anticoagulants + vitamin K: Anticoagulant effect
opposed
• Serotonin syndrome • QT prolongation – can lead to life threatening
cardiac arrhytmia torsade de pointes
• Disturbances in fluid and electrolyte balance– Kalium loosing diuretics + digoxin: Increased
toxicity of digoxin
Probability of drug interaction
0%
10%
20%
30%
40%
50%
60%
2 5 10 15 20
number of drugs used
risk
of dru
g inte
ract
ion
Probability of drug interaction rises with the number of drugs patient uses
Indicence of potencial drug-drug interactions (P DDI) in the population of 120 000 clients of health insurance fund
ZPS
0
2 000
4 000
6 000
8 000
10 000
12 000
14 000
16 000
2001 2002 2003 2004 2005
Inci
dence
of cl
inic
ally
rele
vant P D
DI
0
200
400
600
800
1 000
1 200
1 400
1 600
Indic
ence
of fo
rbid
den
and o
ther
life
th
reate
nin
g P
DD
I
clinically relevant forbidden other life threatening
Why doctors cannot keep drug interactions on
mind?Too many informations:• 2 700 drug interaction in CR,
where coincident therapy is forbidden by manufacturer
• 3 100 drug clinical relevant interactions in CR, where coincident therapy may cause serious damage to patient
Solution is to combine these activities:
• Education of doctors and pharmacits• Cooperation of doctors and pharmacists to
identify high-risk patiens• Feedback to doctors from databases of
health insurance funds• Computer program:
– alerts doctors when potencial drug-drug interaction occurs
– offers the most detailed evidence-based information in the actual time the prescription is written
Questions asked by doctors and pharmacists
• Two drugs interact: Is this knowledge theoretical (speculative) or is it proved in humans (not only in mice or in vitro)? How strong is the proof?
• Clinical relevance: If the interaction occured in humans, how serious is it?
• Has it been described many times or only once?• Are all patients affected or only a few?• Is it best to avoid these two drugs altogether or
can the interaction be accommodated in some way (and how)? Dosing of drugs, lab tests, watching for specific signs and symptoms…
Stockley´s Drug Interactions, Sixth edition
INFOPHARM program offers (I)
• Stratification of the clinical importance of drug interaction (values from 0 to 5, where values 3,4 and 5 are clinically relevant)
• Validation of quality of documentation of drug interaction: – poor evidence– no EBM proof avilable, only manufacturer´s
statement– case-report– good (more than 3 case-reports or a small study)– excelent (study)
• Aggregate evaluation of clinical importance and quality of documentation (values from 0 to 5)
INFOPHARM program offers (II)
• Information, what happens to patient when the two drugs are applied
• Mechanism of drug interaction (if known)• What measures are to be applied to lessen the
risk: Decrease dosing, lab tests provided, watching for specific signs and symptoms, or not to apply the two drugs together at all
• Comments: Abstracts from medical papers containing all the neccessary information for doctor to know how to deal with the situation
• References: Each user can find the primary source of information
The way the information is providedStratification of
quality of documentacion
and clinical relevance
What happens to patient?
Mechanism of interaction
What measures are to be
made?
Abstracts from medical papers are detailed
Sources – to identify the
medical papers
Three ways to use INFOPHARM drug interaction
program• Isolated use of the program• Drug interaction program is used like a
module for other program, such as:– patient notes including medication on PC– pharmacy programs for warehousing
activities• Health insurance funds database use the
program to provide drug prescription analysis and rational drug prescription support to the doctors
Isolated use of drug interactions program
INFOPHARM
Name and number of insurance card of the
patient
Notes (eg. diagnosis, adress of the patient…
Here user writes the name of the medicinal
product
Write first 4 letters and list of drugs
pops up.Scrool down to find the right drug and
then ENTER
List of drugs is being made
Where drug interaction is
identified, line is automatically drawn
Red line: drug interactionBlack line: contraindication!
Number: Clincal relevance of drug
interaction
Program identifies:• Potential drug interactions – red connection-line• Contraindicated drug interactions – black
connection-line• No drug interaction – green connection-line
(evidence from human studies)• 2 or more drugs with the same active ingredient –
blue connection-line• 2 or more drugs with similar active ingredient,
when co-prescription is usually erroneous – violet connection-line
• 2 or more drugs with marked hepatotoxicity, myelotoxicity or nephrotoxicity, when co-prescription is to be avoided – yellow connection-line
Stratification of the risk of drug interactions in ČR and in other
countries
0 no drug interaction1 very small risk A Probably no clinical relevance2 small risk, usually unimportant, in some cases
timing of application of one drug should be changed
B Clinical relevance not completely assessed
3 medium risk, dosing should be changed sometimes, and/ or lab tests, or clinical symptoms watched
4 large risk, usually dosing should be changed, and/ or lab tests, or clinical symptoms watched
5 very large risk, avoid (if possible), and/ or lab tests, clin.symptoms!
6 contraindication
Risk-clasification by INFOPHARM Clinical relevance by FASS
C Clinical relevance. Interaction may modify the effect of the drug, but this is susceptible to control by dose adjustment (includes beneficial and adverse drug interactions)
D Clinically relevant, may serious clinsonsequences, ought to be avoided.
In drug-interaction program filters should be implied
Documented evidence in ČR and in other countries
1 incomplete case-records, or studies with different outcomes (never only analogies, never only in vitro)
2 report from manufacturer, when other information is not avilable
3 complete case-reports 2 well documented case-reports
4 good evidence - small human studies (up to 5 probands)
3 based on studies in volunteers or on pilot studies in patients
5 very good evidence - one or more human studies (6 and more probands)
4 based on controlled studies in relevant patients groups
Documented evidence: FASS
1 incomplete case-records, or in vitro studies, or LI is presumend (evidence from similar drugs)
Evicence-documentation: INFOPHARM
When only clinically relevant interaction are to be identified, press filter button
Buttons for saving the patient medical record and opening
another one
Now filter is set only for
clinical relevant
interactions - level 4 and 5
To get detailed information on the
drug interaction press this button
Examplex of health insurance database report on drug interactions using
INFOPHARM program
Drug interactions
prescribed to patients
which are client of
particular general
practicioner
Lower index: Both drug prescribed by specialistsUpper index: Dr. prescribed both drugs
The same GP:drug
interactions are sorted
by individual patients
INFOPHARM a.s.
• Adress: Hvozdanska 3• Post code number: 148 00• City: Prague 4• Country: Czech Republic• www.drugagency.cz• tel. +420 226 211 791-3, +420 724 375
439 (Prokes Michal, MD)• fax: +420 226 211 794
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