Among all adverse drug reactions reported in clinical practice, which is the most common type in terms of overall frequency?

Question

Accepted Answer

A. Type A (Augmented pharmacological) reactions. ## Frequency Distribution of Adverse Drug Reactions

**Key Point:** Type A (Augmented) reactions account for approximately **80% of all adverse drug reactions** in clinical practice, making them by far the most common type.

### Comparative Epidemiology of ADR Types

| ADR Type | Frequency | Characteristics | Examples |
|----------|-----------|-----------------|----------|
| **Type A (Augmented)** | **~80%** | Dose-dependent, predictable, exaggerated pharmacology | Bleeding on warfarin, hypoglycemia on insulin, dry mouth on anticholinergics |
| **Type B (Bizarre)** | ~15–20% | Dose-independent, unpredictable, immune-mediated | Anaphylaxis, DRESS, SJS/TEN, serum sickness |
| **Type C (Chronic)** | ~5% | Cumulative dose/duration-dependent | Tetracycline photosensitivity, methotrexate hepatotoxicity |
| **Type D (Delayed)** | Rare | Teratogenic or carcinogenic | Thalidomide, methotrexate, diethylstilbestrol |
| **Type E (End-of-dose)** | Uncommon | Withdrawal or rebound phenomena | Rebound hypertension on clonidine withdrawal |

### Why Type A Is Most Common

**High-Yield:** Type A reactions are:
1. **Predictable** — occur in any patient given sufficient dose
2. **Dose-dependent** — severity correlates with drug concentration
3. **Related to pharmacology** — exaggeration of the drug's intended effect
4. **Manageable** — usually reversible by dose reduction or discontinuation

**Mnemonic: ADEC** — **A**ugmented (most common, 80%), **D**elayed (rare), **E**nd-of-dose (uncommon), **C**hronic (5%), **B**izarre (15–20%, but not in alphabetical order — remember B is second most common).

**Clinical Pearl:** In clinical practice, the vast majority of ADRs are preventable Type A reactions caused by:
- Overdosing (renal/hepatic impairment not accounted for)
- Drug–drug interactions
- Polypharmacy in elderly patients
- Failure to adjust dose for age, weight, or organ dysfunction

This is why dose optimization and therapeutic drug monitoring are cornerstone strategies in ADR prevention.

Answer

B. Type B (Bizarre/Idiosyncratic) reactions

Answer

C. Type C (Chronic) reactions

Answer

D. Type E (End-of-dose) reactions

Among all adverse drug reactions reported in clinical practice, which is the most common type in terms of overall frequency?

Explanation

Frequency Distribution of Adverse Drug Reactions

Comparative Epidemiology of ADR Types

Why Type A Is Most Common

Practice similar questions

Join our NEET PG community

ADR Type	Frequency	Characteristics	Examples
Type A (Augmented)	~80%	Dose-dependent, predictable, exaggerated pharmacology	Bleeding on warfarin, hypoglycemia on insulin, dry mouth on anticholinergics
Type B (Bizarre)	~15–20%	Dose-independent, unpredictable, immune-mediated	Anaphylaxis, DRESS, SJS/TEN, serum sickness
Type C (Chronic)	~5%	Cumulative dose/duration-dependent	Tetracycline photosensitivity, methotrexate hepatotoxicity
Type D (Delayed)	Rare	Teratogenic or carcinogenic	Thalidomide, methotrexate, diethylstilbestrol
Type E (End-of-dose)	Uncommon	Withdrawal or rebound phenomena	Rebound hypertension on clonidine withdrawal