ABSTRACT
Methicillin was the first penicillinase-resistant semisynthetic penicillin to be derived from the penicillin nucleus, 6-aminopenicillinic acid (6-APA) (Knudsen and Rolinson, 1960). The drug was discovered at Beecham Research Laboratories. Initially it was used widely, but because of its toxicity, it was gradually superseded by other penicillinase-resistant penicillins, such as nafcillin, oxacillin, cloxacillin, dicloxacillin, and flucloxacillin. Methicillin is now no longer marketed for human use, nor is it produced commercially for testing purposes. The chemical structure is shown in Figure 6.1.
