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Pyrantel Pamoate

Pyrantel Pamoate – Very Useful Drug in Combating Intestinal Parasites

Intestinal parasites, strange as their name may sound, are very frequent, especially in children. A very useful drug in combating them is Pyrantel Pamoate. Here we explain what it is and how it acts.

The pirantel, or more specifically the pamoate of pirantel, constitutes a medicine that deals with intestinal parasitic infections . Its utility lies in paralyzing the muscular system of the parasites . However, it only faces some nematodes.

Mechanism of action

This compound, as we have already said, causes the paralysis of certain parasites . The mechanism by which he carries out this action is double. On the one hand it activates nicotinic receptors, and on the other hand it inhibits acetylcholinesterase.

Parasites in the stomach.

Nicotinic Activity

Nicotinic activity results from the activation of nicotinic receptors. These are a type of cholinergic receptors, which are those that are activated by acetylcholine . Cholinergic receptors are found in many places, but the one that concerns us now is the neuromuscular junction.

The neuromuscular junction corresponds to the area in which a motor nerve and a muscle fiber contact . In this place three parts are identified:

  • Presynaptic neuron, which receives a stimulus and releases the neurotransmitters it contains. In the neuromuscular plate the main neurotransmitter is acetylcholine.
  • Synaptic cleft, where the released neurotransmitters are located.
  • One or more muscle cells, which contain nicotinic receptors, through which acetylcholine is captured.

When the acetylcholine is bound to the nicotinic receptors, a sequence of changes begins. Thus, the cell that contains the nicotinic receptors begins to experience the entrance of positive ions, sodium and potassium, which leads to the so-called depolarization. This promotes the contraction of the cell.

Inhibition of Acetylcholinesterase

Once carried out its action, acetylcholine is free in the synaptic cleft, or is recapped by the presynaptic neuron.

The enzyme acetylcholinesterase also participates in the neuromuscular junction. It is found in the synaptic cleft, where it is responsible for disintegrating acetylcholine. This action prevents acetylcholine from reattaching to the muscle fiber . It also decreases the number of acetylcholine molecules that will bind to the fiber.

So acetylcholinesterase, ultimately, decreases muscle contraction. Since our drug inhibits acetylcholinesterase, its action promotes sustained muscle contraction.

Spastic Paralysis

There are two types of paralysis: flaccid and spastic. The first refers to that paralysis in which the muscles can not contract.

In the second, the one that concerns us, paralysis occurs because the muscles can not stop contracting . Thus, it is impossible to execute any movement because the muscles are paralyzed in a certain position.


This medicine must be taken orally. It is practically not absorbed, that is, it barely passes into the bloodstream of the person who takes it. The minimum part that is absorbed is metabolized in the liver and excreted in the urine.

Thus, from the mouth it passes practically intact to the intestine, where it paralyzes the organisms  that are parasitizing it at that moment. The part of the drug that has not been used is excreted intact in the faeces, as well as the microorganisms in front of which it has acted.

Microorganisms That Combat Piracy

As we have already clarified, the pirantel does not deal with all kinds of parasites . It is effective especially in intestinal parasites due to some types of nematodes. Nematodes are a type of “cylindrical” worms.

Eliminate intestinal worms.

Here are some examples of parasitosis along with their responsible microorganisms.

  • Hookworm:  Ancylostoma duodenale  and  Necator americanus
  • Trichinosis:  Trichinella spiralis
  • Trichosomiasis:  Trichostrongylus orientalis
  • Ascariasis:  Ascaris lumbricoides
  • Enterobiasis:  Enterobius vermicularis

Pyrantel is effective in both humans and animals.

Side Effects

Since the absorption of this drug is minimal, adverse reactions are very rare . However, some of them are:

  • Nausea and vomiting
  • Anorexia  due to lack of appetite
  • Diarrhea
  • Retortijones
  • Bellyache
  • Transient transaminase elevations

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