ANTIWORM PLUS TABLET

Indications

• Schistosomiasis caused by Schistosoma mansoni
• Schistosomiasis caused by Schistosoma japonicum
• Tapeworm infections, including Taenia solium and Hymenolepis nana

Mechanism of action

Praziquantel is hypothesized to target the β subunits of voltage-gated Ca2+ channels in parasites such as Schistosoma mansoni and Schistosoma japonicum. This action leads to increased calcium influx, causing rapid contraction and paralysis of the worms. The drug also induces tegumental disintegration and vacuolization in schistosomes, significantly affecting adult worms more than juveniles. Secondary effects include inhibition of glucose uptake and depletion of glycogen levels.

Pharmacodynamics

Praziquantel exhibits a rapid onset of action against trematodes and cestodes, causing significant changes in the permeability of the cell membrane of the parasites. This results in muscle contraction, tegumental damage, and eventual death of the worms. It selectively targets schistosomes and is ineffective against nematodes. The drug's efficacy is notably reduced against juvenile schistosomes and may diminish after a few weeks of treatment.

Pharmacokinetics

Praziquantel is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1-3 hours post-administration. It undergoes extensive hepatic metabolism, primarily by CYP450 enzymes, and has a half-life of approximately 1-3 hours. The drug is excreted mainly in urine as metabolites, with a small fraction excreted unchanged. The pharmacokinetics can be affected by co-administration with certain other drugs that alter its metabolism.

Adverse effects

• dizziness
• hepatitis
• neutropenia
• seizure
• severe cutaneous adverse reactions

Interactions

• mitotane+praziquantel: Severe (decreases exposure)
• rifampicin+praziquantel: Severe (decreases exposure)
• chloroquine+praziquantel: Moderate (decreases exposure)
• cobicistat+praziquantel: Unknown (increases exposure)
• dexamethasone+praziquantel: Unknown (decreases exposure)
• grapefruit juice+praziquantel: Unknown (increases exposure)
• cimetidine+praziquantel: Unknown (increases exposure)
• idelalisib+praziquantel: Unknown (increases exposure)

Pregnancy

Manufacturer advises avoiding use due to toxicity observed in animal studies.

Breast-feeding

Amount present in milk is too small to be harmful; however, the manufacturer advises avoiding use.

Storage

Store in a cool, dry place away from light.

Formulations

• tablets
• oral suspension

Indications

• Nematode infections
• Cestode infections
• Hookworm infections
• Roundworm infections
• Tapeworm infections

Dosage

Children: Refer to the BNF for Children for pediatric dosing recommendations.

Adults: Refer to the BNF for specific dosing information.

Mechanism of action

Febantel works by inhibiting the polymerization of tubulin into microtubules, which is essential for the parasite's cellular structure and function. This disruption leads to impaired nutrient absorption and ultimately results in the death of the parasite.

Pharmacodynamics

The drug exhibits a selective toxicity towards helminths due to the differences in their microtubule formation compared to mammalian cells. This selectivity allows it to effectively clear parasitic infections while minimizing adverse effects on the host.

Pharmacokinetics

Febantel is well absorbed after oral administration and is extensively metabolized in the liver to its active metabolite, fenbendazole. It has a moderate half-life and is primarily excreted in the feces. The pharmacokinetic profile can be influenced by factors such as the presence of food and the health status of the animal.

Adverse effects

• Vomiting
• Diarrhea
• Lethargy
• Anorexia
• Hypersensitivity reactions

Precautions

• Use with caution in animals with pre-existing gastrointestinal disorders
• Ensure adequate hydration during treatment

Pregnancy

Safety in pregnant animals has not been established, use only if potential benefits outweigh risks.

Breast-feeding

Use with caution in lactating animals, as safety has not been established.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• Tablets
• Oral 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

Although the exact mechanism of action is unknown, praziquantel was hypothesized to target the β subunits of voltage-gated Ca₂₊ channels, particularly in Schistosoma mansoni and Schistosoma japonicum, due to the lack of two conserved serine residues in these subunits. This is supported by the finding that co-administration of calcium channel blockers like nicarpidine and nifedipine renders 50% of Schistosoma mansoni resistant to praziquantel. Increased exposure of antigens on the worm surface was also observed, but little research has been done to elucidate on the mechanism of action.

Pharmacodynamics

In vitro studies on trematodes and cestodes have shown that praziquantel induces a rapid contraction of schistosomas by a specific effect on the permeability of the cell membrane. The drug further causes vacuolization and disintegration of the schistosome tegument. The effect is more marked on adult worms compared to young worms. An increased Ca2⁺-influx may play an important role. Secondary effects are inhibition of glucose uptake, lowering of glycogen levels and stimulation of lactate release. The action of praziquantel is specific to trematodes and cestodes; nematodes (including filariae) are not affected. Praziquantel is active against schistosoma (for example, Schistosoma mekongi, Schistosoma japonicum, Schistosoma mansoni and Schistosoma hematobium), and infections due to the liver flukes, Clonorchis sinensis/Opisthorchis viverrini. Published in vitro data have shown a potential lack of efficacy of praziquantel against migrating schistosomulae. An interesting quirk of praziquantel is that it is relatively ineffective against juvenile schistosomes. While initially effective, effectiveness against schistosomes decreases until it reaches a minimum at 3-4 weeks. Effectiveness then increases again until it is once again fully effective at 6-7 weeks.

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,.