New uses for old drugs.

Existing therapies are often tried when new diseases are discovered or new manifestations of known organisms are recognized. This article reviews the successful application of older commonly used antibiotics to several representative "new" or "newly recognized" illnesses. Examples include new uses for the antistaphylococcal agents, penicillin, the tetracyclines, erythromycin, vancomycin, trimethoprim-sulfamethoxazole, pyrazinamide, metronidazole, clindamycin, and others.