2. Objectives
ā¢ Definition of terms associated with Adverse Drug
Reactions (ADRs)
ā¢ Classification of ADRs
ā¢ Discussion on each type of ADR with examples
3. Definitions
ā¢ Adverse Event (AE): Any untoward medical occurrence
that may present during treatment with a pharmaceutical
product but which does not necessarily have a causal
relationship with this treatment.
ā¢ Adverse Drug Reaction (ADR): Any noxious change
which is suspected to be due to a drug, occurs at doses
normally used in man, requires treatment or decrease in
dose or indicates caution in future use of the same drug.
ā¢ Therefore, an adverse drug reaction is an adverse event
with a causal link to a drug.
4. Drug administered
Pt. develops a new condition/symptom
ADE
Drug suspected?
Yes
Check literature
Documented ?
(for the product
Or
similar class of products)
Yes
Highly suggestive of
ADR
5. Not documented in literature
Drug continued
Worsening of symptoms
Any other possible causes?
ā¢ Concomitant therapy
ā¢ Underlying conditions
Drug discontinued
Symptoms improve
(+ve dechallenge)
Drug restarted
Symptoms recur
(+ve rechallenge)
6. Simplyā¦.
ā¢ Adverse: Untoward, unintended, possibly causing harm
(noxious)
ā¢ AE: Adverse Event, Effect or Experience
ā¢ ADE (Adverse Drug Event): An AE which happens in a
patient taking a drug
ā¢ ADR (Adverse Drug Reaction): An ADE in which a
causal association is suspected between the drug and the
event
7. ADEs Vs ADRs
Adverse drug events
(ADEs)
Adverse Drug
Reactions
(ADRs)
No need to have
a causal relationship
Causal relationship
is suspected/established
8. Classification of ADRs
ā¢ Depending onā¦.
ā¢ Onset of event: Acute (<60 minutes), Sub-acute (1-24 hrs) and
Latent (>2 days)
ā¢ Type of reaction: Type A (Augmented), B (Bizarre), C
(Chemical),D (Delayed), E (Exit), F (Familial), G (Genotoxicity),
H (Hypersensitivity), U (Un classified)
ā¢ Severity: Minor, Moderate, Severe, Lethal ADRs
ā¢ Others: Side effects, Secondary effects, Toxic effects,
Intolerance, Idiosyncrasy, Drug allergy, Photosensitivity, Drug
Dependence, Drug Withdrawal Reactions, Teratogenicity,
Mutagenicity, Carcinogenicity, Drug induced disease (Iatrogenic)
9. Classification of ADRs....
Wills and brown
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ā¢
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Type A (Augmented)
Type B (Bizarre)
Type C (Chemical)
Type D (Delayed)
Type E (Exit/End of treatment)
Type F (Familial)
Type G (Genotoxicity)
Type H (Hypersensitivity)
Type U (Un classified)
10. Type A (Augmented) reactions
ā¢ Reactions which can be predicted from the known
pharmacology of the drug
ā¢ Dose dependent,
ā¢ Can be alleviated by a dose reduction
E.g.
ā¢ Anticoagulants ļ Bleeding,
ā¢ Beta blockers ļ Bradycardia,
ā¢ Nitrates ļ Headache,
ā¢ Prazosin ļ Postural hypotension.
11. Type B (Bizarre) reactions
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Cannot be predicted from the pharmacology of the drug
Not dose dependent,
Host dependent factors important in predisposition
E.g.
ā¢ Penicillin ļ Anaphylaxis,
ā¢ Anticonvulsant ļ Hypersensitivity
12. Type C (Chemical) reactions
ā¢ Biological characteristics can be predicted from the
chemical structure of the drug/metabolite
E.g.
ā¢ Paracetamol ļ Hepatotoxicity
13. Type D (Delayed) reactions
ā¢ Occur after many years of treatment.
ā¢ Can be due to accumulation.
E.g.
ā¢ Chemotherapy ļ Secondary tumours
ā¢ Phenytoin during pregnancy ļ Teratogenic effects
ā¢ Antipsychotics ļ Tardive dyskinesia
ā¢ Analgesics ļ Nephropathy
14. Type E (End of treatment) reactions
ā¢
Occur on withdrawal especially when drug is stopped
abruptly
E.g.
ā¢ Phenytoin withdrawal ļ Seizures,
ā¢ Steroid withdrawal ļ Adrenocortical insufficiency.
15. Classification of ADRsā¦.
Depending on Severity
ā¢ Minor ADRs: No therapy, antidote or prolongation of
hospitalization is required.
ā¢ Moderate ADRs: Requires change in drug therapy, specific
treatment or prolongs hospital stay by atleast 1 day.
ā¢ Severe ADRs: Potentially life threatening, causes
permanent damage or requires intensive medical treatment.
ā¢ Lethal: Directly or indirectly contributes to death of the
patient.
16. Side effects
ā¢ Unwanted but often unavoidable, pharmacodynamic effects
that occur at therapeutic doses
ā¢ Predicted from the pharmacological profile of a drug
ā¢ Known to occur in a given percentage of drug recipients
ā¢ E.g.
ā¢ Side effect based on therapeutic effect:
Atropine (preanaesthetic) ļ dryness of mouth
Acetazolamide (diuretic-bicarbonate excretion) ļ Acidosis
ā¢ Side effect based on a different action:
Promethazine (anti-allergic) ļ sedation
Estrogen (Anti ovulatory) ļ Nausea
ā¢ Depending on the context:
Codeine (anti-tussive) ļ constipation ļ Used in Travellerās
diarrhea
17. Side effectsā¦.
ā¢ Drug discovery
ā¢ Occasionally, āadverseā effects may be exploited to develop an
entirely new indication for a drug.
ā¢ E.g:
ā¢ Unwanted hair growth during Minoxidil treatment of severely
hypertensive patients ļ development of the drug for hair
growth.
ā¢ Sildenafil was initially developed as an antianginal, but its
effects to alleviate erectile dysfunction ļ a new drug indication
in erectile tissue.
ā¢ Sulfonamides used as antibacterials were found to produce
hypoglycemia and acidosis as side effects ļ development of
Hypoglycemic Sulfonylureas and Carbonic anhydrase inhibitor
Acetazolamide.
18. Secondary effects
ā¢ Indirect consequences of a primary action of the drug
ā¢ E.g.
ā¢ Tetracyclines ļ Suppression of bacterial flora
ļ Superinfections
ā¢ Corticosteroids ļ Weaken host defence ļ Activation of
latent tuberculosis
19. Toxic effects
ā¢ Result of excessive pharmacological action of the drug
due to over dosage or prolonged use.
ā¢ Over dosage may be
1.
2.
Absolute (Accidental, homicidal, suicidal)
Relative (Gentamycin in Renal failure)
ā¢ Result from
1. Extension of therapeutic effect:
E.g. Barbiturates ļ Coma,
Digoxin ļ Complete A-V block,
Heparin ļ Bleeding
2. Functional alteration:
E.g. Atropine ļ Delirium
3. Drug induced tissue damage:
E.g. Paracetamol ļ Hepatic necrosis
20. Intolerance
ā¢ Appearance of characteristic toxic effects of a drug in an
individual at therapeutic doses
ā¢ Converse of tolerance,
ā¢ Indicates a low threshold of the individual
ā¢ E.g.
ā¢ Triflupromazine (single dose) ļ Muscular dystonias in
some individuals
ā¢ Carbamazepine (few doses) ļ Ataxia in some individuals
ā¢ Chloroquine (single tablet) ļ Vomiting and abdominal
pain in some individuals
21. Idiosyncrasy
ā¢ Genetically determined abnormal reactivity to a chemical
ā¢ Certain Bizarre drug effects due to peculiarities of an
individual for which no definite genotype has been
described, are also included.
ā¢ Drug interacts with some unique feature of the individual,
not found in majority subjects, and produces the
uncharacteristic reaction.
ā¢ E.g.
ā¢ Barbiturates ļ Excitement and mental confusion in some individuals
ā¢ Quinine ļ Cramps, diarrhea, asthma, vascular collapse in some
individuals
ā¢ Chloramphenicol ļ Aplastic anemia in rare individuals
22. Drug allergy
ā¢ Immunologically mediated reaction producing stereotype
symptoms, unrelated to the pharmacodynamic profile of the drug
ā¢ Generally occur even with much smaller doses
ā¢ Also called Drug hypersensitivity
ā¢ Types:
ā¢ Type I: Immediate, anaphylactic (IgE)
ā¢ E.g: Penicillins ļ Anaphylaxis
ā¢ Type II: Cytotoxic antibody (IgG, IgM)
Humoral
ā¢ E.g: Methyldopa ļ hemolytic anemia
immunity
ā¢ Type III: Serum sickness (IgG, IgM)
ā¢ Antigen-antibody complex
ā¢ E.g: Procainamide-induced lupus
ā¢ Type IV: Delayed hypersensitivity (T cell)
Cell mediated
immunity
ā¢ E.g: Contact dermatitis
23. Photosensitivity
ā¢ Cutaneous reaction resulting from drug induced sensitization of the
skin to UV radiation. The reactions are of two types
ā¢ Phototoxic: Drug or its metabolite accumulates in the skin, absorbs
light and undergoes a photochemical reaction resulting in local tissue
damage (sunburn-like, i.e., erythema, edema, blistering, hyper
pigmentation)
E.g. Tetracyclines (esp. Demeclocycline), and Tar products,
Nalidixic acid, Fluoroquinolones, Sulfones etc
ā¢ Photo allergic: Drug or its metabolite induces a cell mediated
immune response which on exposure to light (longer wave length)
produces a papular or eczematous contact dermatitis like picture.
E.g. Sulfonamides, Sulfonylureas, Griseofulvin, Chloroquine,
Chlorpromazine
24. Drug dependence
ā¢ Drugs capable of altering mood and feelings are liable to repetitive use
to derive euphoria, withdrawal from reality, social adjustment, etc.
ā¢ Psychological dependence: Individual believes that optimal state of
well being is achieved only through the actions of the drug.
ā¢ E.g. Opioids, Cocaine.
ā¢ Physical dependence: Altered physiological state produced by
repeated administration of a drug which necessitates the continued
presence of the drug to maintain physiological equilibrium.
Discontinuation of the drug results in a characteristic withdrawal
(abstinence) syndrome.
ā¢ E.g. Opioids, Barbiturates, Alcohol, Benzodiazepines
25. Drug dependenceā¦.
ā¢ Drug abuse: Use of a drug by self medication in a manner and
amount, that deviates from the approved medical and social
patterns in a given culture at a given time.
Drug abuse refers to any use of an illicit drug.
ā¢ Drug addiction: Compulsive drug use characterized by
overwhelming involvement with the use of a drug.
ā¢ Drug habituation: Less intensive involvement with the drug,
withdrawal produces only mild discomfort.
ā¢ Habituation and addiction imply different degrees of
psychological dependence.
26. Drug withdrawal reactions
ā¢ Sudden interruption of therapy with certain drugs result in
adverse consequences, mostly in the form of worsening
of the clinical condition for which the drug was being
used.
ā¢
ā¢
ā¢
ā¢
E.g:
Corticosteroid ļ Adrenal insufficiency
Ī²-blockers ļ worsening of angina, precipitation of MI
Clonidine ļ severe HTN, restlessness, sympathetic over
activity
27. Teratogenicity
ā¢ Capacity of a drug to cause foetal abnormalities when
administered to the pregnant mother.
ā¢ Drugs can affect the foetus at 3 stages:
1. Fertilization and implantation (Conception to 17 days):
failure of pregnancy which often goes unnoticed.
2. Organogenesis(18 days to 55 days): most vulnerable period,
deformities are produced.
3. Growth and development (> 56 days): developmental and
functional abnormalities can occur.
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E.g:
Thalidomide ļ Phocomelia, multiple defects
Anticancer drugs ļ Cleft palate, hydrocephalus, multiple defects
ACE inhibitors ļ Hypoplasia of organs (lungs, kidney)
28. Mutagenecity and
Carcinogenicity
ā¢ Capacity of a drug to cause genetic defects and
cancer respectively.
ā¢ Chemical carcinogenesis generally takes several
(10-40) years to develop.
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ā¢
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ā¢
E.g.
Anticancer drugs,
Radio-isotypes,
Estrogens,
Tobacco.
29. Drug induced disease
ā¢ Also called Iatrogenic(Physician induced) diseases.
ā¢ Functional disturbances caused by drugs which persist
even after the offending drug has been withdrawn and
largely eliminated
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E.g.
Salicylates, Corticosteroids ļ Peptic ulcer
Phenothiazines, other antipsychotics ļ Parkinsonism
Isoniazid ļ Hepatitis
Hydralazine ļ DLE
30. Summary
ā¢ Adverse Drug Reactions (ADRs) are adverse events with a
causal link to a drug.
ā¢ Types of Classification of ADRs:
ā¢ Onset of event: Acute (<60 minutes), Sub-acute (1-24 hrs) and
Latent (>2 days)
ā¢ Type of reaction: Type A (Augmented), B (Bizarre), C
(Chemical),D (Delayed), E (Exit), F (Familial), G (Genotoxicity),
H (Hypersensitivity), U (Un classified)
ā¢ Severity: Minor, Moderate, Severe, Lethal ADRs
ā¢ Others: Side effects, Secondary effects, Toxic effects,
Intolerance, Idiosyncrasy, Drug allergy, Photosensitivity, Drug
Dependence, Drug Withdrawal Reactions, Teratogenicity,
Mutagenicity, Carcinogenicity, Drug induced disease
(Iatrogenic)