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Anthelmintic Studies with Pyrantel. II. Prophylactic Activity in a Mouse-Ascaris suum Test Model

Harold L. Howes, Jr.
The Journal of Parasitology
Vol. 57, No. 3 (Jun., 1971), pp. 487-493
DOI: 10.2307/3277899
Stable URL: http://www.jstor.org/stable/3277899
Page Count: 7
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Anthelmintic Studies with Pyrantel. II. Prophylactic Activity in a Mouse-Ascaris suum Test Model
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Abstract

Mouse lung lesions were graded (0 to 5 according to severity) and the numbers of larvae per lung were determined at various time intervals after inoculation of 5,000 embryonated A. suum ova. It was concluded that 8 days post-infection (p.i.) is the optimal time for measuring the effect of drug treatment on the severity of pathology. The straight line obtained from a semilog plot of 8-day p.i. lesion scores and inoculum size (500 to 5,000 ova) was used as a standard curve. The effectiveness of a given treatment on the average lesion score of a treated group was expressed as a percent reduction in inoculum effectiveness. Using a multiple dose regimen pyrantel HCl was shown to be very active (minimum effective dose = 0.5 mg/kg) against the larvae present in the intestinal lumen (hatching larvae). Subsequent studies revealed that when administered within 1 hr after ova inoculation a single dose at a given mg/kg level is virtually equal in effectiveness to multiple doses given at hourly intervals. Studies in which mice were killed at various time intervals, 15 to 120 min p.i., showed that after 60 min many embryonated ova and hatched larvae are below the ileocecal junction. Thus a dose administered within the first 60 min affords soluble compounds such as pyrantel HCl the maximum pharmacokinetic opportunity to exert an anthelmintic effect. With either the single or multiple dose regimen pyrantel HCl was found to posssess a unique degree of activity when compared to piperazine, tetramisole, and thiabendazole. When administered in the feed for 7 hr, commencing 2 hr before ova inoculation, its minimum effective concentration was 0.005%. The reference compounds were only effective at concentrations in excess of 0.1%.

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