Antihelmithic drugs Flashcards
What are the three major groups of helminths that infect humans?
The three major groups of helminths are: Nematodes (e.g., Ascaris lumbricoides, Enterobius vermicularis, Ancylostoma duodenale). Trematodes (e.g., Schistosoma haematobium, Schistosoma mansoni, Schistosoma japonicum). Cestodes (e.g., Taenia saginata, Taenia solium, Echinococcus).
What is the mechanism of action of Mebendazole?
Mebendazole blocks glucose uptake in parasites, leading to energy depletion, immobilization, and death of the worms.
What are the pharmacokinetics of Mebendazole?
Available as chewable tablets and suspension. Poor absorption (only 10%) from the gut, making it mainly active against intestinal worms. Fatty food increases absorption, so it is better administered between meals.
What are the side effects of Mebendazole?
Generally well-tolerated but may cause abdominal pain and diarrhea. Contraindicated in children below 2 years and during pregnancy due to potential embryotoxicity and teratogenicity.
What is the clinical use of Mebendazole for Enterobius vermicularis (pinworm)?
A single dose of 100 mg, repeated after 2 weeks. Good hygiene practices and treating all family members are important to prevent reinfection.
What is the mechanism of action of Albendazole?
Albendazole impairs glucose uptake in intestinal parasites, leading to their immobilization and slow death. Its metabolite, albendazole sulfoxide, is larvicidal in hydatid disease, cysticercosis, ascariasis, and hookworm infections.
What are the pharmacokinetics of Albendazole?
Administered orally, with absorption increased by fatty meals. Metabolized in the liver to albendazole sulfoxide, which distributes well to tissues, including hydatid cysts and the CNS. Plasma half-life: 8-12 hours. Metabolites are excreted in urine.
What are the side effects of Albendazole?
Short-term use (1-3 days): No significant adverse effects. Long-term use (e.g., for hydatid disease): Risk of hepatotoxicity, agranulocytosis, or pancytopenia. In neurocysticercosis, it may cause inflammatory responses (e.g., headache, vomiting, convulsions).
What are the contraindications for Albendazole?
Pregnancy. Children under 2 years. Liver disease. Known hypersensitivity.
What is the current use of Thiabendazole?
Thiabendazole is now limited to the topical treatment of cutaneous larva migrans (creeping eruption) due to its toxic effects.
What is the mechanism of action of Praziquantel?
Praziquantel increases cell membrane permeability to calcium, causing marked contraction followed by paralysis of the worm musculature, leading to death.
What are the side effects of Praziquantel?
Drowsiness, dizziness, malaise, GIT upsets, and anorexia. Contraindicated in pregnancy, breastfeeding, and ocular cysticercosis.
What is the mechanism of action of Niclosamide?
Niclosamide inhibits the parasite’s mitochondrial phosphorylation of ADP, leading to energy depletion, immobilization, and death of the cestode.
What is the drug of choice for Onchocerciasis (river blindness)?
Ivermectin is the drug of choice for Onchocerciasis. It binds to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing paralysis and death of the parasite.
What are the side effects of Diethylcarbamazine?
Initial reactions include vomiting, headache, urticaria, fever, and asthmatic attacks due to the release of antigenic particles from dying parasites.
What is the mechanism of action of Levamisole?
Levamisole causes depolarization followed by paralysis of the worm musculature, leading to the expulsion of live worms in the feces by normal peristalsis.
What are the side effects of Levamisole?
Generally well-tolerated but may cause abdominal pain, nausea, vomiting, headache, and dizziness.
What is the mechanism of action of Piperazine?
Piperazine blocks acetylcholine at the neuromuscular junction of Ascaris, causing paralysis and expulsion of the live worm by normal peristalsis.
What are the adverse effects of Piperazine?
GI disturbances. Neurotoxicity, allergic reactions, and serum sickness-like syndrome. Contraindicated in epilepsy, chronic neurologic disease, pregnancy, and malnutrition.
What is the mechanism of action of Ivermectin?
Ivermectin binds to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing paralysis and death of the parasite. It is effective in a single dose and does not cross the blood-brain barrier.
