Feed intake effect

Extending the duration of drug-digesta passage prolongs drug availability in the gastrointestinal tract. Reducing feed intake of sheep increases the half-life of rumen fluid and particulate digesta from 6.5 to 11 h and from 12 to 18 h, respectively (Ali and Hennessy, 1996), to prolong drug absorption, whether originating from passage from the rumen or after secretion in gastric, biliary and enteric secretions. Compared with sheep consuming full feed intake, orally administering ivermectin 24 h after feed withdrawal extended the Tmax from 22 to 38 h, increased the AUC from 1399 to 2085 (ng ml-1) x h and extended the elimination half-life from 12 to 34 h. Similarly, Alvinerie et al. (2000) significantly increased the availability of moxidectin when horses were fasted before oral administration. The practice of feed withdrawal before oral treatment broadens the pharmacokinetic profile, significantly increasing anthelmintic efficacy.

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