Core8: Adverse drug reactions

⚠️ High-yield / 要点：ADR classification: A = Augmented, B = Bizarre, C = Chronic, D = Delayed, E = End-of-use, F = Failure.

Side effect vs adverse effect / 副作用と有害作用

• Side effect：unintended effect; can be therapeutic or harmful.
• Adverse effect / ADR：harmful, undesirable effect; may limit treatment or cause complications.
• ADRs are generally more severe and clinically important than mild self-resolving side effects.

ADR types / ADR分類

Type	Mnemonic	Feature	Management
A	Augmented	Dose-related, predictable, related to pharmacology	Reduce dose or stop drug
B	Bizarre	Non-dose-related, unpredictable, often immunologic/idiosyncratic	Stop and avoid in future
C	Chronic	Dose- and time-related; cumulative exposure	Reduce dose or withdraw gradually
D	Delayed	Appears after time delay	Often difficult to treat
E	End-of-use	Withdrawal reaction after stopping drug	Reintroduce and taper slowly
F	Failure	Unexpected lack of therapy, often due to dose or interactions	Increase dose or check interactions

Important examples / 重要例

• Type A：digoxin toxicity, serotonin syndrome with SSRIs, anticholinergic effects of TCAs.
• Type B：penicillin hypersensitivity, malignant hyperthermia, pseudoallergy.
• Type C：HPA-axis suppression by corticosteroids.
• Type D：teratogenesis, carcinogenesis, tardive dyskinesia.
• Type E：opioid withdrawal, myocardial ischemia after β-blocker withdrawal.
• Type F：oral contraceptive failure with enzyme inducers.

Severe hypersensitivity syndromes / 重篤な過敏反応

• DRESS：drug reaction with eosinophilia and systemic symptoms; often anticonvulsants or antimicrobials.
• SJS：immune-mediated blistering and epidermal detachment; triggers include antibiotics, antiepileptics, allopurinol.
• TEN：SJS with >30% skin involvement; risk of hypovolemic/septic shock.
• Disulfiram-like reaction：metronidazole + alcohol.

Remember / 覚え方

• A = predictable dose problem
• B = unpredictable allergy/idiosyncrasy
• E = withdrawal after ending
• F = therapy fails