Antibiotic-associated neutropenia.

Neutropenia is an uncommon but potentially serious complication of drug therapy. Many drugs, especially antibiotics, can produce this untoward effect. Typically, drug-induced neutropenia occurs in a patient receiving a semisynthetic penicillin for two weeks or more. The cause is believed to be either a hypersensitivity reaction or a toxic dose-related suppression of white blood cell precursors. Most patients improve after discontinuation of the drug.