FURTHER PHARMACOLOGY AND CHEMOTHERAPY OF CLOXACILLIN

In concentrations greatly in excess of therapeutic blood levels cloxacillin has a slight hypotensive action. As with other antibiotics, it sometimes causes diarrhoea in rabbits but, in doses up to 200 mg/kg, it does not have a teratogenic effect on the rabbit foetus. Cloxacillin is distributed throughout the body. High concentrations are found only in the liver and kidney, these reflecting the high concentrations in the bile and urine respectively. It differs from other penicillins investigated in that there appears to be little or no renal tubular secretion as demonstrated in experiments on the hen. Cloxacillin is excreted as the unchanged drug and as an active metabolite in the urine and bile. After oral administration it is metabolized in the caecum giving a penicillin which differs from the urinary metabolite and which has a greater antibiotic action against Sarcina lutea than the parent penicillin. The activity of the caecal metabolite against resistant and sensitive strains of Staphylococcus, however, remains similar to that of cloxacillin. Against infections due to resistant and sensitive Staphylococcus in animals cloxacillin is active by both the oral and subcutaneous routes and it is more effective orally than an equal subcutaneous dose of methicillin.