Pyrantel is a highly effective antihelmintic drug for enterobiasis, ascardiasis, ankylostomiasis, and necatoriasis. The antihelmintic effect is exhibited in the form of a powerful cholinomimetic effect on muscle cells of nematodes by binding with their cholinergic receptors,
which leads to inhibition of neuromuscular transmission in the parasite, contraction of
their musculature, and as a result, in the removal of the helminthes from the gastrointestinal tract of the host. It heals 85–100% of cases of ascariasis, and 90–100% of cases of
enterobiasis. It is the drug of choice for Enterobius vermicularis, Acaris lumbricoides, as
well as Ancylostoma duodenale, and Necator americanus. Synonyms of this drug are
helmex, combantrin, antiminth, and others.
Pharmazeutische Anwendungen
A tetrahydropyrimidine, formulated as the pamoate (embonate)
in a 1:1 ratio and available as a suspension for oral administration.
It is practically insoluble in water, but soluble in
dimethyl sulfoxide. It is stable at room temperature.
Pharmakokinetik
By synthetic design most of the dose is passed unchanged in
the feces. The portion that is absorbed (<5%) is metabolized
and excreted in the urine.
Clinical Use
Ascariasis
Pinworm
Hookworm (especially A. duodenale)
Trichostrongyliasis
Higher and more prolonged doses may be necessary in hookworm
infection caused by N. americanus. Pyrantel has been
used in combination with an analog (oxantel) where concurrent
whipworm infection was likely.
Nebenwirkungen
Pyrantel should not be used at the same time as piperazine as
their modes of action are antagonistic. Gastrointestinal upsets
and, rarely, very mild neurological symptoms occur.
Synthese
Pyrantel, 1,4,5,6-tetrahydro-1-methyl-2-[trans-2-(2-thienyl)vinyl]-pyrimidine
(38.1.22), a derivative of tetrahydropyrimidine, is made from 3-(2-thienyl)-acrylonitrile
(38.1.19), which is made in a Knoevangel condensation of furfural with cyanoacetic acid.
Acidic hydrolysis of this makes 3-2(-thienyl)acrylamide (38.1.20). Reacting this with
propansulfone gives an iminoester (38.1.21), which when reacted with N-methyltrimethylenediamine gives the desired pyrantel.
