Penicillins and Cephalosporins
Penicillins and Cephalosporins Acting mainly on gram +ve organisms BETA LACTAM ANTIBIOTICS • Beta lactam ring + thiazolidine ring • Penicillins: 6 amino penicillanic acid nucleus • Cephalosporins = 7 CSA (cephalosporanic acid) • Beta lactam ring constant • Penicillins • Cephalosporins • Carbapenems, Monobactams • Good therapeutic index • PENICILLINS: Mechanism of action • Bind to cytoplasmic membrane binding proteins(PBP) (Penicillin binding protein) • Inhibit transpeptidation reactions in cross linkage of peptidoglycans required for cell wall synthesis • Also activate autolytic enzymes to cause lesions inn the cell wall/membrane INTERACTIONS • PENICILLIN or CEPHALOSPORINS • Not combined with aminoglycosides in a syringe- in vitro – pharmaceutical interaction – • Penicillin/ Penicillin/cepha/macrolides macrolides inactivate inactivate - aminoglycosides / tetracyclines / chloramphenicol • Synergism with aminoglycosides • Probenecid inhibits tubular secretion Narrow spectrum • Penici