Table I.

Classification of adverse drug reactions as proposed by Rawlins and Thompson (4).

Type A	Type B
85-90% of ADR	10-15% of ADR
Predictable, related to the pharmacological action of the drug;	Unpredictablea;
Can affect any individual if they are administered at a certain dose or at a certain rate	Independent of pharmacological action;
	Immunologically mediated hypersensitivity reactions or mediated by other mechanisms occurring in susceptible patients
Examples: Nephrotoxicity caused by aminoglycosides, digestive side effects secondary to NSAID therapy	Examples:
	1. Intolerance reactions or low tolerance threshold
	2. Idiosyncratic reactions
	3. Immune-mediated (allergic) reactions

^aWith some exceptions, certain HLA haplotypes are associated with side effects to certain drugs, such as carbamazepine, abacavir, dapsone, allopurinol. ADR, adverse drug reactions; NSAIDs, non-steroidal anti-inflammatory drugs.