The original beta-lactam antibiotic
Penicillin G / benzylpenicillin - destroyed by gastric acid, so parenteral use
Penicillin V / phenoxymethylpenicillin- oral use
Penicillinase resistant penicillins (flucloxacillin)
used to treat infections by susceptible staphylococci
Extended-spectrum penicillins
ampicillin,amoxicillin - activity also against Eschericia and proteus species
ticarcillin, piperacillin - active against Pseudomonas, Klebsiella, Enterobacter species
Use of beta-lactamase inhibitors - tazobactam (Tazocin), clavulanic acid (Co-amoxiclav) can increase activity of these penicillins