What is the difference between a drug allergy, drug intolerance, and an idiosyncratic drug reaction?
All three are types of adverse drug reactions. A true drug allergy is an immunologically mediated adverse reaction to a drug. It can occur with very small doses of the offending agents and accounts for only 5-6% of all adverse drug reactions. Drug intolerance, which also can occur with very small doses, is the result of an undesirable pharmacologic effect of the drug. An idiosyncratic drug reactions is based on an individual patient’s biochemical alterations of a drug’s metabolism.