Chemical Properties
Pale yellow or yellow powder.
Uses
An antiparasitic agent used in the treatment of intestinal parasites such as hookworms and roundworms (Ascaris lumbricoides, aka ascarids in humans) in domesticated animals such as horses, cattle, sheep, pigs, cats, dogs, and many other species.
Brand name
Antiminth (Roerig); Combantrin (Pfizer).
General Description
Odorless light yellow to tan crystalline powder. Tasteless. Used medicinally against nematodes in animals.
Air & Water Reactions
May be sensitive to prolonged exposure to air and light . Insoluble in water.
Reactivity Profile
Pyrantel pamoate may react with acids to liberate heat. May react exothermically enough with strong oxidizing acids to ignite the reaction products. Heat is also generated with caustic solutions. Generates flammable or toxic gases with alkali metals and hydrides and other reducing agents.
Fire Hazard
Flash point data for Pyrantel pamoate are not available; however, Pyrantel pamoate is probably combustible.
Description
Pyrantel is a tasteless,
odorless, yellow, crystalline solid. It is insoluble
inwater, slightly soluble in dimethylformamide,
and soluble in dimethyl sulfoxide.
Definition
ChEBI: Pyrantel pamoate is an organic molecular entity.
Indications
Pyrantel pamoate (Antiminth) is a agonist at the nicotinic
acetylcholine receptor, and its actions result in depolarization
and spastic paralysis of the helminth muscle.
Its selective toxicity occurs primarily because the
neuromuscular junction of helminth muscle is more
sensitive to the drug than is mammalian muscle. This
drug is administered orally, and because very little is absorbed,
high levels are achieved in the intestinal tract.
Less than 15% of the drug and its metabolites are excreted
in urine.
Mechanism of action
Pyrantel is a depolarizing neuromuscular
blocking agent. In nematodes it causes a slowly
developing contraction and paralysis. The immobilized
parasites are then eliminated from the
intestine. The neuromuscular junction of Ascaris
is 100-fold more sensitive to pyrantel than to
acetylcholine .
Clinical Use
Trans-1,4,5,6,-Tetrahydro-1-methyl-2-[2-(2 -thienyl)ethenyl]pyrimidine pamoate (Antiminth) is a depolarizing neuromuscularblocking agent that causes spastic paralysis insusceptible helminths. It is used in the treatment of infestationscaused by pinworms and roundworms (ascariasis).Because its action opposes that of piperazine, the twoanthelmintics should not be used together. More than halfof the oral dose is excreted in the feces unchanged.Adverse effects associated with its use are primarilygastrointestinal.
Side effects
Pyrantel pamoate is active against several roundworms:
A. lumbricoides, Ancylostoma duodenale, Necator
americanus, and E. vermicularis. Pyrantel is an alternative
drug of choice in treating infections with A. lumbricoides,
E. vermicularis (pinworms), and hookworms
(N. americanus and A. duodenale). It is not recommended
for pregnant patients or for children under age
1 year.
Although most of the drug remains in the intestinal
lumen, enough can be absorbed systemically to cause
headache, dizziness, and drowsiness. No major adverse
effects have been reported on renal, hepatic, or hematological
systems.
Veterinary Drugs and Treatments
Pyrantel has been used for the removal of the following parasites
in dogs: ascarids (Toxocara canis, T. leonina), hookworms
(Ancylostoma caninum, Uncinaria stenocephala), and stomach
worm (Physaloptera). Although not approved for use in cats, it is
useful for similar parasites and is considered safe to use.
Pyrantel is indicated (labeled) for the removal of the following
parasites in horses: Strongylus vulgaris and equinus, Parasacaris
equorum, and Probstymayria vivapara. It has variable activity
against Oxyuris equi, S. edentatus, and small strongyles. Pyrantel is
active against ileocecal tapeworm (A. perfoliata) when used at twice
the recommended dose, although resistance has been reported.
Although there are apparently no pyrantel products approved
for use in cattle, sheep, or goats, the drug is effective (as the tartrate)
for the removal of the following parasites: Haemonchus spp.,
Ostertagia spp., Trichostrongylus spp., Nematodirus spp., Chabertia
spp., Cooperia spp. and Oesophagostomum spp.
Pyrantel tartrate is indicated (labeled) for the removal or prevention
of the following parasites in swine: large roundworms (Ascaris
suum) and Oesophagostomum spp. The drug has activity against the
swine stomach worm (Hyostrongylus rubidus).
Although not approved, pyrantel has been used in pet birds and
llamas. See the Dosage section for more information.
