PYRANTEL PAMOATE, PYRANTEL TARTRATE

Chemistry - A pyrimidine-derivative anthelmintic, pyrantel pamoate occurs as yellow to tan solidand is practically insoluble in water and alcohol. Pyrantel tartrate is more water soluble than is thepamoate salt. Each gram of pyrantel pamoate is approximately equivalent to 347 mg (34.7%) of thebase.
Pyrantel pamoate may also be known as pyrantel embonate.

Storage, Stability, Compatibility

Pyrantel pamoate products should be stored in tight, light-resistant containers at room temperature (15-30°C) unless otherwise directed by the manufacturer.

Pharmacology - PYRANTEL PAMOATE, PYRANTEL TARTRATE

Pyrantel acts as a depolarizing neuromuscular blocking agent in susceptibleparasites, thereby paralyzing the organism. The drug possesses nicotine-like properties and actssimilarly to acetylcholine. It also inhibits cholinesterase.
Uses, Indications - 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 similarparasites and is considered to be safe to use.
Pyrantel is indicated (labeled) for the removal of the following parasites in horses: Strongylusvulgaris and equinus., Parasacaris equorum, and Probstymayria vivapara. It has variable activityagainst Oxyuris equi., S. edentatus and small strongyles. Pyrantel is active against ileocecaltapeworm (A. perfoliata) when used at twice the recommended dose.
Although there are apparently no pyrantel products approved for use in cattle, sheep, or goats, thedrug 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 inswine: large roundworms (Ascaris suum) and Oesophagostomum spp.. The drug also has activityagainst the swine stomach worm (Hyostrongylus rubidus).
Although not approved, pyrantel has been used in pet birds and llamas. See the Dosage sectionfor more information.

Pharmacokinetics - PYRANTEL PAMOATE, PYRANTEL TARTRATE

Pyrantel pamoate is poorly absorbed from the GI tract, thereby allowing it toreach the lower GI in dogs, cats and equines. Pyrantel tartrate is absorbed more readily than thepamoate salt. Pigs and dogs absorb pyrantel tartrate more so than do ruminants, with peak plasmalevels occurring 2-3 hours after administration. Peak plasma levels occur at highly variable times inruminants.
Absorbed drug is rapidly metabolized and excreted into the urine and feces.
Contraindications/Precautions/Usage in Pregnancy - Use with caution in severely debilitatedanimals. The manufacturers usually recommend not administering the drug to severely debilitatedanimals.
Pyrantel is considered to be safe to use during pregnancy and in nursing animals.

Adverse Effects, Warnings

When administered at recommended doses, adverse effects are unlikely. Emesis may occur however, in small animals receiving pyrantel pamoate.

Overdosage, Acute Toxicity

Pyrantel has a moderate margin of safety. Dosages up to approximately 7 times recommended generally result in no toxic reactions. In horses, doses of 20 timesthose recommended yielded no adverse effects. The LD50 in mice and rats for pyrantel tartrate is170 mg/kg and is >690 mg/kg for pyrantel pamoate in dogs.
Chronic dosing of pyrantel pamoate in dogs resulted in symptoms when given at 50 mg/kg/day, but not at 20 mg/kg/day over 3 months. Symptoms of toxicity that could possibly be seen includeincreased respiratory rates, profuse sweating (in animals able to do so), ataxia or other cholinergiceffects.

Drug Interactions

Because of similar mechanisms of action (and toxicity), pyrantel is recommended not to be used concurrently with morantel or levamisole.
Observation for adverse effects should be intensified if used concomitantly with anorganophosphate or diethylcarbamazine.
Piperazine and pyrantel have antagonistic mechanisms of action; do not use together.