15. Adverse Drug Reactions (ADRs) - Definition, types. Importance for clinical practice · Clinical Pharmacology · MU Sofia

15. Adverse Drug Reactions (ADRs) - Definition, types. Importance for clinical practice.

Defines an adverse drug reaction and separates it from a side effect, then explains why ADRs matter clinically, with rough figures on how often they occur and how many admissions they cause. A table sets out the Rawlins–Thompson mechanistic types A to F with features and examples. It also covers seriousness, frequency bands as used in the SmPC, expectedness and the term SUSAR, and closes with prevention measures.

Inside: 4 sections · 1 table · 15 flashcards · 2 min

Topic 15 of 30 in the MU Sofia syllabus for Clinical Pharmacology (Medicine, Year 5). The free AceMed note covers it in 4 sections, about 235 words (2 min of reading), with 15 flashcards.

Introduction

An adverse drug reaction (ADR) is a response to a medicine that is noxious and unintended. In the EU this includes reactions at normal doses, and also from off-label use, overdose, misuse, abuse and medication errors. A side effect is any unintended effect at normal doses related to the drug's pharmacology; unlike an ADR, it may sometimes be useful (e.g. the sedation of an antihistamine at night).

Why they matter

Up to 35% of patients have ADRs during treatment; serious ADRs in about 6–7%.
About 5–10% of hospital admissions are caused by ADRs; ADRs are a significant cause of death.
About half are preventable.

Classification

By mechanism (Rawlins–Thompson, extended)

Other classifications

Seriousness: a serious ADR causes death, is life-threatening, needs or prolongs hospitalisation, causes persistent disability or a congenital anomaly (or needs intervention to prevent these). Do not confuse it with severity (mild, moderate, severe: how intense it is).
Frequency (as in the SmPC): very common > 1/10; common 1/100–1/10; uncommon 1/1,000–1/100; rare 1/10,000–1/1,000; very rare < 1/10,000.
Expectedness: expected (listed in the SmPC) or unexpected. A SUSAR is a Suspected Unexpected Serious Adverse Reaction.