Pyrantel

Products

Pyrantel is commercially available in the form of chewable tablets and oral suspension and is available in many countries without a doctor’s prescription (Cobantril, originally: Combantrin). It has been approved since 1971 and is also commonly used as a veterinary drug.

Structure and properties

Pyrantel (C11H14N2S, Mr = 206.3 g/mol) is present in the drugs as pyrantelembonate (= pyrantelpamoate), a pale yellow to yellow powder that is practically insoluble in water. It is a tetrahydropyrimidine and thiophene derivative. Pyrantel pamoate and pyrantelembonate are the same substance, namely the salt of pyrantel with the embonic acid (= pamoic acid).

Effects

Pyrantel (ATC P02CC01) has anthelmintic properties against mature and immature worms. It is predominantly effective in the intestine because it is poorly absorbed. The effects are due to neuromuscular blockade, resulting in paralysis and excretion of the worms. Pyrantel is not effective against worm eggs. The molecular drug target of the drug is the nicotinic acetylcholine receptor (nAChR) on the parasitic muscle, to which pyrantel binds as an agonist. This leads to depolarization, hypercontractions, and muscle paralysis.

Indications

For the treatment of gastrointestinal infestation with worms:

  • Pinworm
  • Roundworm
  • Hookworm
  • American hookworm
  • Threadworms

Dosage

According to the professional information. The dosage is based on the patient’s body weight and the causative parasite. The drug is usually administered as a single dose and independently of meals (Switzerland: during or after a meal).

  • In case of infestation with pinworms, the treatment should be repeated after two to three weeks.
  • For treatment of infestation with American hookworms, a two- to three-day treatment is recommended.
  • It is not necessary to take a laxative.
  • Close contacts should be treated under certain circumstances.
  • Suspension is available for children under two years of age.

Contraindications

  • Hypersensitivity
  • Pre-existing liver damage
  • Infants younger than 6 months of age (not studied)

For complete precautions, see the drug label. Pregnancy and lactation: see FI.

Interactions

Piperazine should not be administered concomitantly. Another interaction has been described with theopylline (increase in plasma concentration).

Adverse effects

The most common possible adverse effects include headache, dizziness, abdominal cramps, diarrhea, nausea, vomiting, and transient elevation of transaminases.