CEPHALOSPORINS These are a group of semisynthetic antibiotics derived from &;cephalosporin-C&; obtained from a fungus Cephalosporium. They are chemically related to penicillins; the nucleus consists of a P-lactam ring fused to a dihydrothiazine ring, (7-aminocephalosporanic acid). By addition of different side chains at position 7 of [3-lactam ring (altering spectrum of activity) and at position 3 of dihydrothiazine ring (affecting pharmacokinetics), a large number of semisynthetic compounds have been produced. Cefoperazone: Like ceftazidime, it differs from other third generation compounds in having stronger activity on Pseudomonas and weaker activity on other organisms. It is good for S. typhi and B. fragilis also, but more susceptible to Beta lactamases. The indications are-severe urinary, biliary, respiratory, skin-soft tissue infections, meningitis and septicaemias. It is primarily excreted in bile; half life is 2 hr. It has hypoprothrombinaemic action but does not affect platelet function. A disulfiram-like reaction with alcohol has been repoed. Dose: 1-3 g i.m./i.v. 8-12 hourly ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:705,706