Pyrantel
**Pyrantel** is a broad-spectrum anthelmintic widely used in veterinary medicine for the control of gastrointestinal nematodes, specifically ascarids (roundworms) and hookworms (*Toxocara canis*, *Toxascaris leonina*, *Uncinaria stenocephala*, and *Ancylostoma caninum*). It is frequently formulated in combination with **febantel** or **oxantel** to expand its spectrum of activity to include whipworms (*Trichuris vulpis*), or with praziquantel to target tapeworms. > **Clinical Pearl:** Pyrantel is poorly absorbed from the gastrointestinal tract. This pharmacokinetic property is highly beneficial, as it allows the drug to reach high concentrations in the gut lumen where the target parasites reside, while minimizing systemic exposure and contributing to a wide margin of safety in the host.
Mecanismo: Pyrantel acts as a **depolarizing neuromuscular blocking agent** in susceptible parasites. It functions as a **cholinergic agonist** at the nicotinic acetylcholine receptors of the nematode → causes continuous depolarization of the parasite's muscle cell membrane → results in **spastic paralysis** of the worm. The paralyzed parasites lose their attachment to the intestinal wall and are subsequently expelled from the host's gastrointestinal tract via normal peristalsis.
Dosificación por especie
- Control of Toxocara canis, Toxascaris leonina, Trichuris vulpis, Uncinaria stenocephala, and Ancylostoma caninum · 5 mg/kg pyrantel + 15 mg/kg febantel or 20 mg/kg oxantel · PO · repeat as required · Single dose, repeat as required · Often administered as a combination product.
- Control of susceptible gastrointestinal nematodes · 57.5 mg/kg pyrantel embonate · PO · repeat as required · Single dose, repeat as required · Equivalent to approximately 20 mg/kg pyrantel base.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Puppies < 2 months of age
- Puppies < 1 kg body weight
- Pregnant animals (safety not established)
- Lactating animals (safety not established)
Efectos adversos
- Vomiting
- Diarrhoea
Interacciones farmacológicas
- Febantel · Synergistic effect against whipworms · null
- Oxantel · Synergistic effect against whipworms · null
- Piperazine · Antagonistic mechanisms of action (piperazine causes flaccid paralysis, pyrantel causes spastic paralysis) · major
- Levamisole · Similar mechanism of action; concurrent use increases the risk of cholinergic toxicity · major
- Cholinesterase inhibitors · Increased risk of cholinergic toxicity · major
Monitorización
- Resolution of clinical signs (e.g., diarrhea, poor weight gain)
- Fecal flotation/egg counts to confirm parasite clearance
Sobredosis
Due to its poor gastrointestinal absorption, pyrantel has a wide margin of safety. Massive overdosage may result in systemic cholinergic signs, including **salivation, vomiting, tremors, ataxia, and dyspnea**. Treatment is supportive and symptomatic.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.