pyrantel-pamoate and Oesophagostomiasis

The pharmacokinetic disposition of pyrantel after intravenous (i.v.) and oral (p.o.) administration as the citrate and p.o. administration as the pamoate salt was determined in pigs. Following i.v. administration pyrantel was quickly cleared from the bloodstream, exhibiting a terminal half-life of 1.75 +/- 0.19 h and a residence time (MRT) of 2.54 +/- 0.27 h. After p.o. administration as the citrate salt, the absorption time (MAT) of pyrantel was 2.38 +/- 0.25 h and although significant quantities of pyrantel were absorbed (mean bioavailability of 41%) the rapid clearance resulted in a MRT of only 4.92 +/- 0.36 h. By comparison, the significantly extended MAT of the less soluble pamoate salt resulted in reduced circulating concentrations and a significantly lower mean bioavailability of 16%. The poor efficacy of pyrantel citrate against nematodes inhabiting the large intestine of pigs is therefore suggested to result from insufficient quantities of drug passaging to the site of infection. When tested against pyrantel-resistant adult Oesophagostomum dentatum the mean efficacy of pyrantel citrate was only 23%, whereas the efficacy of the lesser absorbed pyrantel pamoate was 75%. These results indicate that for maximum activity pyrantel should be administered to pigs as the pamoate salt.

Topics: Administration, Oral; Animals; Antinematodal Agents; Biological Availability; Drug Resistance; Female; Half-Life; Injections, Intravenous; Kinetics; Male; Metabolic Clearance Rate; Oesophagostomiasis; Oesophagostomum; Pyrantel; Pyrantel Pamoate; Swine; Swine Diseases

In northern Togo and northeastern Ghana, Oesophagostomum bifurcum is a common parasite in humans. Diagnosis is based on coproculture because the eggs of hookworm and Oesophagostomum are indistinguishable. To determine the level of egg production, 12 subjects were treated with 2 x 10 mg/kg of pyrantel pamoate and the worms they evacuated were then counted. Pretreatment and post-treatment species-specific egg counts were calculated on the basis of larval and total egg counts. The median worm burden was 81 (range 12-300) per person. The calculated median egg production was 33.7 egg/gram of feces per female worm. Assuming a total daily stool production of 150 g/day, this amounts to 5,055 eggs/day, which is comparable with the production of other nematodes of the same superfamily.

Topics: Ancylostomatoidea; Animals; Cathartics; Feces; Female; Humans; Larva; Oesophagostomiasis; Oesophagostomum; Oviposition; Parasite Egg Count; Pyrantel Pamoate; Togo