Pharmacokinetic behaviour and anthelmintic efficacy of 1-n-butyl carbamoyl oxfendazole given by intramuscular injection.

Oxfendazole (OFZ) was chemically modified to 1-n-butyl carbamoyl OFZ (C4-OFZ) in an attempt to improve the solubility of OFZ and enable it to be administered by injection. After intramuscular injection to sheep and cattle, C4-OFZ was metabolised to OFZ which resulted in higher plasma OFZ concentrations that persisted for a considerably longer period than those observed following administration of OFZ orally. The anthelmintic efficacy of injected C4-OFZ was tested, in sheep, against strains of Trichostrongylus colubriformis, Haemonchus contortus and Ostertagia circumcincta, which were highly resistant to benzimidazoles. In all cases, the C4-OFZ treatment showed a significant improvement in efficacy over the conventional oral OFZ drench.