Triclabendazole (TCBZ), administered orally, has been used
to control liver fluke (Fasciola hepatica) for more than
two decades.1
Although some anthelmintics, namely
levamisole and various macrocyclic lactones, have been successfully
delivered by topical (pour-on) application, TCBZ has been thought
unsuitable for such application because of its need for rapid
absorption from the gastrointestinal tract and first-pass hepatic
metabolism.2
It has been estimated for ivermectin that between 58%
and 87% of the topical dose is ingested by self- and allo-grooming.3,4
Recently, topical formulations of TCBZ, in combination with
abamectin or ivermectin, have been developed and marketed in
Australia, but there is little published information on their efficacy or
bioavailability relative to the oral formulations. Topical application
of anthelmintics to cattle provides producers with a very convenient
means of treatment and where such products are available, they
quickly become the preferred method of usage. It is desirable
however, that these products are as effective as the oral alternatives.