Adverse Drug Reaction

According to WHO, response to a drug that is noxious and unintended and that occurs at doses used in humans for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiologic function
excludes therapeutic failures, overdose, drug abuse, noncompliance, and medication errors
Adverse drug effects are classified on the basis of type, severity & onset
According to onset they are classified into
Onset of event:
Acute
within 60 minutes
Sub-acute
1 to 24 hours
Latent
> 2 days


According to severity
Severity of reaction:
Mild
bothersome but requires no change in therapy
Moderate
requires change in therapy, additional treatment, hospitalization
Severe
disabling or life-threatening
FDA Serious ADR
Result in death
Life-threatening
Require hospitalization
Prolong hospitalization
Cause disability
Cause congenital anomalies
Require intervention to prevent permanent injury
According to type

Type A
extension of pharmacologic effect
often predictable and dose dependent
responsible for at least two-thirds of ADRs
e.g., propranolol and heart block, anticholinergics and dry mouth

Type B
idiosyncratic or immunologic reactions
rare and unpredictable
e.g., chloramphenicol and aplastic anemia

Type C
associated with long-term use
involves dose accumulation
e.g., phenacetin and interstitial nephritis or antimalarials and ocular toxicity

Type D
delayed effects (dose independent)
Carcinogenicity (e.g., immunosuppressants)
Teratogenicity (e.g., fetal hydantoin syndrome)

Types of allergic reactions
Type I – immediate, anaphylactic (IgE)
e.g., anaphylaxis with penicillins
Type II – cytotoxic antibody (IgG, IgM)
e.g., methyldopa and hemolytic anemia
Type III – serum sickness (IgG, IgM)
antigen-antibody complex
e.g., procainamide-induced lupus
Type IV – delayed hypersensitivity (T cell)
e.g., contact dermatitis

Common causes of ADR
Antibiotics
Antineoplastics*
Anticoagulants
Cardiovascular drugs*
Hypoglycemics
Antihypertensives
NSAID/Analgesics
Diagnostic agents
CNS drugs*
*account for 69% of fatal ADRs

By Dr. Ahmad Najmi