A comparison of subcutaneous and intraperitoneal oxytetracycline injection methods for control of infectious disease in the rat

After receiving once daily intraperitoneal (i.p.) or subcutaneous (s.c.) injections of oxytetracycline (15 mg/100 g bodyweight) for 7 days, laboratory rats had significantly different oxytetracycline serum levels depending on the method of injection. Regardless of injection method, the biological half-life of the antibiotic was 4·25 h and serum antibiotic levels never fell below therapeutic levels for certain rat pathogens during 24 h post-injection. Severe peritonitis and cellulitis were found in rats whether injected s.c. or i.p. and some animals lost bodyweight. It appeared that either injection method would be an effective treatment for certain infectious diseases of laboratory rats but tissue damage, probably from oxytetracycline's acidity, made both methods unattractive.