The disposition of pyrantel in the gastrointestinal tract and effect of digesta flow rate on the kinetic behaviour of pyrantel in the pig

Pigs consuming a diet with slow digesta transit time were orally administer ed with molar equivalent doses of pyrantel as the citrate and pamoate salt. At appropriate intervals pigs were killed and the quantitative-time distri bution of pyrantel throughout the gut contents was determined. Compared wit h the citrate, there appeared to be greater quantities of the less soluble pamoate salt in the small and large intestine. An additional group of pigs fed on diets with "slow" or "fast" digesta transit time were orally treated with molar equivalent amounts of pyrantel as the citrate and pamoate salt and the respective kinetic disposition of pyrantel in peripheral plasma and quantitative excretion in faeces was determined. The diet type had little effect on pyrantel availability after administration of the less soluble pa moate salt. However, the maximum concentration of pyrantel in plasma was lo wer and there appeared to be greater quantities of pyrantel retained in the gut and excreted in faeces when the citrate salt was orally administered t o pigs fed the "fast" compared to the "slow" diet. Since it is the quantity of pyrantel contained in the gut lumen which is believed to affect efficac y against gastrointestinal parasites, greater efficacy with this anthelmint ic should be obtained when pigs are consuming a high fibre diet. (C) 2000 E lsevier Science B.V. All rights reserved.