Except for the sulfonamides, penicillin is the oldest antibacterial agent available, has been in general clinical use for nearly a quarter of a century, and has been administered to several hundred million people. However, since its inception, many antimicrobial drugs with the same or similar antibacterial spectrum have been discovered, raising the question as to whether other drugs might be superior to penicillin. In the minds of some, this question has been reinforced by the recent decision of the NAS-NRC Drug Efficacy Review Panel that penicillin-sulfonamide and penicillin-streptomycin combinations are not efficacious.1
Penicillin is uniformly bactericidal in low concentrations against group A streptococci, pneumococci, nonpenicillinase-producing staphylococci, meningococci, and, in somewhat higher concentrations, gonococci, and certain enteric bacteria. It is also a potent treponemocidal agent. Translated into the clinical setting, this means that penicillin is highly effective in most cases of exudative pharyngitis, otitis media, pneumonia, meningitis (except for infants