Drug intolerance

Drug intolerance or drug sensitivity is a lower threshold to the normal pharmacologic action of a drug. It is not to be confused with drug allergy. Drug intolerance is uncommon and idiopathic, thus extremely difficult to predict except in persons with a prior history or a family history of intolerance to that specific drug. Some drug intolerances are known to result from genetic variants of drug metabolism.

Examples

 * Tinnitus after a normal dose of aspirin
 * Liver failure (possibly also kidney failure) after a normal dose of acetaminophen
 * Fatal poisoning in a breastfed newborn baby due to normal use of codeine by the mother.

Analgesic intolerance
Intolerance to analgesics, particularly NSAIDs, is relatively common. Its cause is believed to be variation in the metabolism of arachidonic acid. Symptoms include chronic rhinosinusitis with nasal polyps, asthma, gastrointestinal ulcers, angioedema, and urticaria.