PRAZISAM PLUS

Indications

• Intestinal nematodes
• Cestodes
• Helminth infections in veterinary practice

Dosage

Children: Refer to the BNF for Children for appropriate dosing recommendations for paediatric patients.

Adults: Refer to the BNF for specific dosing guidelines, as adult doses may vary depending on the type of infection being treated.

Mechanism of action

Fenbendazole exerts its antiparasitic effects by binding to beta-tubulin in parasites, leading to microtubule destabilization and inhibiting tubulin polymerization. This process disrupts cellular functions, including glucose uptake and energy management, particularly in the anterior intestine, where it is most effective due to its poor absorption following oral administration.

Pharmacodynamics

The primary pharmacodynamic action of fenbendazole involves its ability to alter the structure and function of microtubules in parasitic cells. By inhibiting the polymerization of tubulin, fenbendazole interferes with various cellular processes, including mitosis and the transport of secretory vesicles. This ultimately results in the death of the parasites, as they are unable to maintain essential cellular functions.

Pharmacokinetics

Fenbendazole has low oral bioavailability due to poor absorption from the gastrointestinal tract. It undergoes hepatic metabolism and is excreted primarily in the faeces. The duration of action is affected by the persistence of the drug in the intestinal lumen, where it maintains its anthelmintic effects.

Pregnancy

Fenbendazole is not recommended during pregnancy due to potential risks to the developing fetus.

Breast-feeding

It is not known whether fenbendazole is excreted in human milk. Caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• {'formulation': 'Powder for oral suspension', 'strength': 'Various strengths available'}
• {'formulation': 'Tablets', 'strength': 'Various strengths available'}

Indications

• Schistosomiasis
• Cysticercosis
• Diphyllobothriasis
• Hymenolepiasis
• Other cestode and trematode infections

Dosage

Children: Refer to the BNF for Children for appropriate dosing recommendations in paediatric populations.

Adults: Refer to the BNF for specific dosing guidelines based on the condition being treated and patient factors.

Mechanism of action

Praziquantel acts by increasing the permeability of the cell membrane of the parasites to calcium ions, resulting in a rapid influx of calcium. This leads to muscle contraction and paralysis of the parasite, facilitating its detachment from the host's tissues and subsequent elimination from the body. Additionally, praziquantel induces tegumental damage in the parasites, further enhancing their susceptibility to immune responses.

Pharmacodynamics

The pharmacodynamics of praziquantel involves its effect on the neuromuscular system of helminths, leading to paralysis and death. The increase in calcium ion permeability causes hypercontractility of the muscular system in the parasites, while the drug also inhibits their ability to adhere to host tissues, allowing for easier clearance by the host's immune system.

Pharmacokinetics

Praziquantel is rapidly absorbed from the gastrointestinal tract after oral administration, with peak plasma concentrations occurring within 1-2 hours. It is extensively metabolized in the liver to active metabolites. The elimination half-life of praziquantel is approximately 1.5 to 2.5 hours. The metabolites are primarily excreted in the urine, with a smaller fraction eliminated in the feces. Its pharmacokinetic profile is influenced by factors such as liver function and the presence of food, which can enhance absorption.

Contra-indications

• Hypersensitivity to praziquantel or any of the excipients
• Severe liver dysfunction

Adverse effects

• Nausea
• Vomiting
• Abdominal pain
• Dizziness
• Headache
• Fatigue
• Rash
• Pruritus

Interactions

• Cimetidine may increase praziquantel levels
• Anticonvulsants may decrease praziquantel efficacy due to increased metabolism
• Rifampicin may reduce plasma concentrations of praziquantel

Precautions

• Use with caution in patients with liver impairment
• Monitor for potential allergic reactions
• Consider potential interactions with other medications

Pregnancy

Praziquantel is classified as category B. Animal studies have not demonstrated a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women.

Breast-feeding

Praziquantel is excreted in human milk, caution should be exercised when administering to nursing mothers.

Storage

Store in a tightly closed container at room temperature, away from moisture and heat.

Formulations

• Tablets
• Suspension

Indications

• Ascariasis
• Enterobiasis (pinworm infection)
• Hookworm infections
• Strongyloidiasis (off-label use)

Dosage

Children: For children aged 2 years and older, the recommended dose is usually 10 mg/kg (up to a maximum of 1 g) given as a single dose. For children under 2 years, refer to the BNF for Children for specific dosing guidance.

Adults: The standard adult dose for treating pinworm or roundworm infections is typically 10 mg/kg (up to a maximum of 1 g) as a single dose.

Mechanism of action

Pyrantel promotes the release of acetylcholine, inhibits cholinesterase, and stimulates ganglionic neurons, acting as a depolarizing neuromuscular blocking agent in helminths. This leads to extensive depolarization of the helminth muscle membrane, causing muscle tension and subsequent paralysis, which facilitates the expulsion of the parasites from the intestine.

Pharmacodynamics

Pyrantel exhibits properties akin to both competitive and depolarizing neuromuscular blocking agents, leading to spastic paralysis of the helminths. The drug induces marked and persistent activation of nicotinic receptors in the parasites, which results in their inability to maintain attachment to the intestinal walls.

Pharmacokinetics

Pyrantel is administered orally and is minimally absorbed from the gastrointestinal tract, which enhances its effectiveness against intestinal parasites. The majority of the drug remains in the gut, where it acts on the parasites directly. The metabolites and unabsorbed drug are excreted in the feces, primarily through normal peristalsis.

Adverse effects

• Nausea
• Vomiting
• Abdominal cramps
• Diarrhea
• Dizziness
• Headache
• Rash

Precautions

• Use with caution in patients with liver disease
• Not recommended for use in cases of known hypersensitivity to pyrantel or its components
• Monitor for signs of allergic reactions

Pregnancy

Pyrantel is classified as pregnancy category C. Animal studies have shown an adverse effect, and there are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Pyrantel is excreted in breast milk. Caution is advised when administering to nursing mothers, as the effects on the nursing infant are not well studied.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Pyrantel pamoate oral suspension
• Pyrantel pamoate tablets

Mechanism of action

Due to its poor absorption by oral administration, fenbendazole is particularly effective for targeting intestinal parasites. It exerts its antiparasitic effects primarily in the anterior intestine by depolymerizing microtubules, inhibiting intestinal secretory vesicle transport. When fenbendazole binds to beta-tubulin in parasites, it causes microtubule destabilization and hinders tubulin polymerization. This destabilization disrupts cellular function, such as glucose uptake, and thus affects the energy management of parasites.

Mechanism of action

By promoting the release of acetylcholine, inhibiting cholinesterase, and stimulating ganglionic neurons, pyrantel serves as a depolarizing neuromuscular blocking agent in helminths. This causes extensive depolarization of the helminth muscle membrane, resulting in tension to the helminth's muscles, leading to paralysis and release of their attachment to the host organism intestinal walls. This action is unlike piperazine, which is a hyperpolarizing neuromuscular blocking agent that causes relaxation of the helminth muscles, leading to a subsequent detachment from the intestinal wall. Excretion of the parasites in the feces occurs by normal peristalsis. PYRANTEL & ITS ANALOGS ARE DEPOLARIZING NEUROMUSCULAR BLOCKING AGENTS. THEY INDUCE MARKED, PERSISTENT ACTIVATION OF NICOTINIC RECEPTORS, WHICH RESULTS IN SPASTIC PARALYSIS OF THE WORM. PYRANTEL ALSO INHIBITS CHOLINESTERASES. /PYRANTEL PAMOATE AND ANALOGS/ PYRANTEL ... CAUSES A SLOWLY DEVELOPING CONTRACTURE OF PREPARATIONS OF ASCARIS AT 1% OF THE CONCENTRATION OF ACETYLCHOLINE REQUIRED TO PRODUCE THE SAME EFFECT. IN SINGLE MUSCLE CELLS OF THIS HELMINTH, PYRANTEL CAUSES DEPOLARIZATION & INCREASED SPIKE-DISCHARGE FREQUENCY, ACCOMPANIED BY INCREASE IN TENSION.

Pharmacodynamics

It has similar properties to both competitive and depolarizing neuromuscular blocking agents, which leads to the understanding of the paralytic effect of the drug has on parasites, ultimately resulting in the death of the parasite,.