Adverse drug reaction

ADVERSE DRUG REACTION
Dr. Subhash R. Yende
Asst. Professor,
Gurunanak College of Pharmacy, Nagpur
1
Dr.SubhashR.Yende,GNCP,Nagpur

Definition
 Any undesirable or unintended consequence of
drug administration
 Any noxious change which is suspected to be due
to a drug, occurs at doses normally used in man,
for treatment, prophylaxis, diagnosis of disease.
 Adverse effects are more common with multiple
drug therapy, after prolonged medication or even
after stoppage of the drug and in the elderly
patients
 an incidence of 10–25% has been documented
2

Reasons for adverse drug reaction
 Dispensing and medication error
 Failure to set therapeutic endpoint
 Bioavailability differences
 Patients factors
3

Classification
 Predictable (Type A or Augmented) reactions
 Excessive pharmacological effects
 Secondary pharmacological effects
 Rebound effect on discontinuation
 Unpredictable (Type B or Bizarre) reactions
 Allergic drug reactions
 Idiosyncrasy
 Genetically determined toxicity
4

Excessive pharmacological Effects (Toxic effects)
 Due to overdosage or prolonged use
 Overdosage may be absolute (accidental, homicidal,
suicidal) or relative (i.e. usual dose in presence of renal
failure, age range, lower albumin level etc)
 Examples-
 Coma by barbiturates
 Complete A-V block by digoxin
 Bleeding due to heparin
 Morphine (analgesic) causes respiratory failure in overdosage
 Phenytoin (anticonvulsant) cause memory impairment after
prolong used
5
Predictable reactions

Secondary pharmacological effects (Side effects)
 Unwanted but often unavoidable pharmacodynamic
effects that occur at therapeutic doses
 can be predicted from the pharmacological profile of a
drug
 Reduction in dose, usually ameliorates the symptoms
 Examples- postural hypotension caused by prazosin;
promethazine produces sedation
 Sometime side effect may be based on the same action
as the therapeutic effect, e.g. atropine is used in
preanaesthetic medication for its antisecretory action;
codeine used for cough produces constipation as a side
effect, but the latter is its therapeutic effect in traveller’s
diarrhoea 6

Rebound effect on discontinuation
 Chronic use of certain drugs produces drug dependence
and addiction
 Drugs producing dependence are-opioids, barbiturates
and other depressants including alcohol and
benzodiazepines
 Amphetamines, cocaine, cannabis are drugs which
produce addiction
 Sudden interruption of therapy with certain other drugs
also results in adverse consequences (Withdrawal
effects)
 Severe hypertension, restlessness and sympathetic over
activity may occur shortly after discontinuing clonidine ;
Frequency of seizures may increase on sudden
withdrawal of an antiepileptic
7

Allergic drug reactions
 An immunologically mediated reaction producing
stereotype symptoms which are unrelated to the
pharmacodynamic profile of the drug
 occur only in a small proportion of the population exposed
to the drug
 The drug or its metabolite acts as an antigen (AG), or
more commonly a hapten (incomplete antigen: drugs
have small molecules which become antigenic only after
binding with an endogenous protein) and induce
production of antibody (AB)/sensitized lymphocytes
 Eg. Drugs like Penicillins , Aspirin, Sulfonamides – urticaria,
itching, rashes on skin
 Tetracyclin cause dermatitis
 Penicillins, LA causes respiratory difficulties
 Methyldopa, quinidine cause anemia 8
Unpredictable reactions

Idiosyncrasy
 Genetically determined abnormal reactivity to a chemical
 The drug interacts with some unique feature of the
individual, not found in majority of subjects, and produces
the uncharacteristic reaction
 The type of reaction is restricted to individuals with a
particular genotype
 e.g.:
 Barbiturates cause excitement and mental confusion in
some individuals
 Quinine/quinidine cause cramps, diarrhoea, asthma,
angioedema of face and hypotension in some patients
 Analgesics may induced tumors of kidney in patients with
renal disease
9

Genetically determined toxicity
 In case of patients with special genotype or genetic make up,
there is risk of drug toxicity
 Example –
 Hereditary deficiency of pseudocholinestrase are unable to
metabolize the succinyl-choline and may develop prolonged
paralysis and apnoea following its use
 Glucose 6 phosphate dehydrogenase is an enzyme which is
involved in the degradation of glucose. Such patients can
develop hemolytic anemia after use of primaquine, quinidine,
sulfonamide and nitrofurantoin
 Isoniazid metabolised in the liver by the enzyme N-acetyl
transferase. In the population, some 1ndividuals are slow
acetylators and some fast acetylators. Slow acetylators of
isoniazide may suffer from peripheral neuropathy. 10

ADR Reporting and Management
ADR detection:
 Adverse effects resulting from excessive
pharmacological activity are well documented.
 But unpredictable adverse effects are not identified, until
it has been subjected to much more widespread use.
 Collection of Patients data either by-
 Patient interview
 Reviewing prescriptions containing drugs
 Checking for abrupt cessation of any medications
 Obtaining previous medical history
11

 Data to be collected includes-
 Patient’s demographic data; presenting complaints; past
medication history; drug therapy details including
over‐the‐counter drugs, current medications and
medication on admission; and lab data such as
hematological, liver and renal function tests
 Details of the suspected adverse drug reaction such as
time of onset and duration of reaction, nature and severity
of reaction;
 Details of the suspected drug including dose, frequency,
time of administration, duration of treatment, plasma
concentration of drug;
 Previous reports on reported reactions;
12

ADR Reporting:
 What to report ?
 Serious and or life threatening reactions
 Fatal reactions
 Reactions resulted in disabilities/ permanent harm
 Reactions resulted in increased healthcare costs
 Severe reactions of any type
 Any reactions to newer drugs
 Newer reactions to any drugs in the market
 Rare and uncommon adverse reactions
13

 Different approaches for ADR reporting are-
1. Cohort study: This study involve short term and long
term clinical trials and post marketing surveillance of
established and new drug.
2. Spontaneous reports of suspected adverse drug
reaction occurs when prescribers report suspected
reaction to investigator agency
3. Review of vital statistics: Regular review of national
and regional vital statistics
4. Case-control studies: patients with suspected drug
induced disease are compared with a reference
population
14

Management of ADR:
 Decisions are made by considering
 Seriousness / severity of ADR
 Seriousness of disease
 Benefit / harm assessment
 If the reaction is serious -
 Withdraw suspected (all?) drugs
 Treat urgently
15

 If the disease is serious -
 Consider the effect of not having treatment
 Continue treatment and treat symptoms of reaction if
necessary
 Consider an alternative drug
 Stop unnecessary drugs
 If the reaction is mild –
 Continue treatment if necessary
 Stop unnecessary drugs
 Consider dose reduction
 Reassure and do nothing
 Symptomatic treatment if warranted
16

Management of ADR (Summary)
17

Reference
 K.D. Tripathi, Essentials of Medical Pharmacology,
Eighth Edition, Jaypee Brothers Medical Publishers (P)
Ltd
 A.R. Paradkar and S.A. Chunawala Hospital and
clinical pharmacy, Nirali Prakashan.
 https://www.slideshare.net/KatlaSwapna/detection-
reporting-and-management-of-adverse-events
18

Adverse drug reaction

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