SEMISYNTHETIC PENICILLINS

Produced by chemically combining specific side chains in place of benzyl side chain of PnG
Procaine Pn & benzathine Pn are salts of PnG & not semisynthetic Pn
The aim is to overcome the shortcomings of PnG which are:
Poor oral efficacy
Susceptibility to beta lactamase
Narrow spectrum
Hypersensitivity reactions
CLASSIFICATION
Acid resistant alternative to PnG: Phenoxy methyl Pn / PnV
Penicillinase/ beta lactamase resistant Pn: Methicillin, Cloxacillin
Extended spectrum Pn
1. Amino Pn: Ampicillin, Bacampicillin, Amoxycillin
2. CarboxyPn: Carbenicillin, Ticarcillin
3.UreidoPn: Piperacillin, Mezlocillin
ANTI-staphylococcal penicillins
“semi-synthetic”
Add bulky side chains to provide
STERIC HINDRANCE
(Methicillin) - renal toxicity
Nafcillin
Oxacillin
Cloxacillin (di-clox) - oral drugs
Beta lactamases inhibitors: Clavulanic acid, Sulbactam, Tazobactam
Ampicillin:
Spectrum: all organism which are sensitive to PnG + H. influenzae, E.coli, proteus, Salmonella & Shigella
PK: not degraded by gastric juice so given orally, partly excreted in bile & reabsorbed, enterohepatic circulation occurs, primary channel of excretion is kidney
USES
UTI
RTI
Meningitis
Gonorrhoea
Typhoid fever
Bacillary desentry d/t Shigella
Cholecystitis
SABE
Septicemia & Mixed infection