According to Rawlins and Thompson classification, which type of adverse drug reaction is dose-dependent and occurs in individuals with normal drug metabolism?

Explanation

## Rawlins and Thompson Classification of Adverse Drug Reactions **Key Point:** Type A reactions are dose-dependent, predictable, and occur in individuals with normal drug metabolism and pharmacokinetics. ### Type A (Augmented) Reactions - **Definition:** Exaggerated pharmacological response to the drug at normal or high doses - **Dose-dependent:** Yes — increase in dose increases risk - **Predictability:** Highly predictable; occur in normal population - **Mechanism:** Excessive pharmacological effect due to: - High drug concentration - Individual sensitivity variation - Drug-drug interactions - Organ dysfunction (renal/hepatic impairment) - **Examples:** - Hypoglycaemia from excessive insulin - Bleeding from warfarin overdose - Hypotension from antihypertensives - Dry mouth from anticholinergics - **Incidence:** 80% of all ADRs - **Management:** Dose reduction or drug withdrawal ### Comparison with Other Types | Feature | Type A | Type B | Type C | Type D | |---------|--------|--------|--------|--------| | **Dose-dependent** | Yes | No | No | No | | **Predictable** | Yes | No | Yes | Yes | | **Incidence** | 80% | 15% | 3% | 2% | | **Mechanism** | Pharmacological | Idiosyncratic | Cumulative | Genetic/Delayed | | **Examples** | Bleeding (warfarin) | Aplastic anaemia (chloramphenicol) | Pulmonary fibrosis (bleomycin) | Phocomelia (thalidomide) | **High-Yield:** Type A reactions are the most common (80%) and most predictable — they follow the dose-response relationship and can be prevented by dose adjustment or careful monitoring. **Clinical Pearl:** Type A reactions are reversible upon dose reduction or drug withdrawal, making them less serious than Type B reactions despite being more common.