Plasma pharmacokinetics, faecal excretion and efficacy of pyrantel pamoate paste and granule formulations following per os administration in donkeys naturally infected with intestinal strongylidae

The plasma disposition, faecal excretion and efficacy of two formulations of pyrantel pamoate in donkeys were examined in a controlled trial. Three groups of seven donkeys received either no medication (control) or pyrantel paste or granule formulations at horse dosage of 20mg/kg B.W. (equals 6.94mg/kg PYR base) of body weight. Heparinized blood and faecal samples were collected at various times between 1 and 144h after treatment. The samples were analysed by high-performance liquid chromatography. The last detectable plasma concentration (tmax) of paste formulation was significantly earlier (36.00h) compared with granule formulation (46.29h). Although, there was no significant difference on terminal half lives (t1/2: 12.39h vs. 14.86h), tmax (14.86h vs. 14.00) and MRT (24.80h vs. 25.44h) values; the Cmax (0.09μg/ml) AUC (2.65μgh/ml) values of paste formulation were significantly lower and smaller compared with those of granule formulation (0.21μg/ml and 5.60μgh/ml), respectively. The highest dry faecal concentrations were 710.46μg/g and 537.21μg/g and were determined at 48h for both paste and granule formulation of PYR in donkeys, respectively. Pre-treatment EPG of 1104, 1061 and 1139 were observed for the control, PYR paste and PYR granule groups, respectively. Pre-treatment EPG were not significantly different (P>0.1) between groups. Post-treatment EPG for both PYR treatment groups were significantly different (P<0.001) from the control group until day 35. Following treatments the PYR formulations were efficient (>95% efficacy) until day 28. In all studied donkeys, coprocultures performed at day—3 revealed the presence of Cyathostomes, S. vulgaris. Faecal cultures performed on different days from C-group confirmed the presence of the same genera. Coprocultures from treated animals revealed the presence of few larvae of Cyathostomes.