Introduction

Drugs seldom exert their beneficial effects without also causing one or more adverse drug reactions (ADRs). Major mechanisms of ADRs include (1) “on-target” adverse reactions, (2) “off-target” adverse reactions, (3) cytotoxic reactions, (4) immune-mediated reactions, and (5) idiosyncratic reactions.¹ In Adverse Drug Reactions – Part I, the discussion focused on mechanisms (1), (2), and (3) and related common ADRs that can occur with therapeutic doses of drugs in the top 200 dispensed by U.S. community pharmacies in 2008.²

In Adverse Drug Reactions – Part II, the discussion is extended to mechanisms (4) immune-mediated reactions and (5) idiosyncratic reactions, and related common ADRs that occur with drugs in the top 200 dispensed by U.S. community pharmacies in 2008, and to less commonly noted ADRs affecting oral tissues. In addition, a brief discussion of the mechanisms of uncommon, time-related (delayed), and usually dose-related ADRs, i.e., carcinogenesis and teratogenesis, and some secondary ADRs are presented.