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The objective of this study was to determine the pharmacokinetic behaviour of imidocarb in horses following a single i.m. injection at the dose commonly administered to treat Babesia caballi infections or to prevent babesiosis. Eight horses were injected i.m. with a single dose of 2.4 mg imidocarb dipropionate/kg bwt and blood, faecal, urine and milk samples were collected. For imidocarb determination, a high-performance liquid chromatographic method (HPLC) was used after weak cation-exchange solid phase, or liquid-liquid, extraction procedures. Twelve hours after treatment, no detectable plasma concentrations were recorded in any of the treated animals. The distribution and elimination patterns of the drug suggested that it is quickly sequestrated in some storage tissues and remains in the body for a long time. Its prolonged presence in the body may confer a reservoir effect to imidocarb in some tissues, therefore making it undetectable in the plasma of animals but sufficient to produce its described therapeutic and prophylactic activities.

A comparison of the efficacy of imidocarb dipropionate solution and tetracycline hydrochloride in the treatment of naturally occurring ehrlichiosis of dogs presented at the University of Nairobi small animal clinic was carried out. Five to 7 mg per kg imidocarb dipropionate given intramuscularly twice at an interval of 14 days was as effective as 14 daily, oral doses of 66 mg per kg tetracycline hydrochloride in alleviating the clinical signs of disease. Imidocarb eliminated the infection in 81 per cent of the cases whereas tetracyclines cleared only 25 per cent as judged by cell culture isolation. Imidocarb had the further advantage of controlling concurrent babesiosis. The majority of dogs showed some transient side-effects after administration of imidocarb, while a small proportion of dogs dosed with tetracycline reacted adversely and dosage had to be reduced or stopped.