Antihelmintic drugs

Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may also be called vermifuges or vermicides.

💭💭Helminthiasis is prevalent globally, but more common in developing countries due to poor personal and environmental hygiene.They are commonly transmitted through feco- oral route. ☠☠☠☠

👉Classification of antihelmintic drugs:

According to mode of action :

A) Inhibits ATP synthesis by inhibiting glucose uptake

• Albendazole

• Mebendazole

• Thiabendazole

B) Paralysis of worm and expel in feces

1. Neuromuscular blocker

• Pyrantel pamoate

2. Increased influx of Cl- by activating GABA receptor

• Ivermectin

3. Increased permeability of cell membrane of worm to Ca2+

• Praziquantel

C) Destroy scolex

• Niclosamide

👉Mechanism of action of albendazole/mebendazole:

•Albendazole/mebendazole inhibits microtubule synthesis in nematodes.

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Irreversibly impair glucose uptake by the worm

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ATP synthesis required for survival

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Parasites are immobilised or die slowly

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Cleared out from intestine within 2-3 days

✔✔Indications of albendazole /mebendazole :

• Ascaris, hook worm, Enterobius, Trichuris infestations

• Tapeworm and Strongyloides infestations

• Neurocysticercosis

• Cutaneous and visceral larva migrans

• Hydatid disease

• Filariasis

♻♻Adverse effects of albendazole/mebandazole:

• Diarrhoea, nausea, abdominal pain

• Expulsion of Ascaris from mouth and nose has occurred

• Allergic reactions, loss of hair, granullocytopenia may occur at high dose.

❎ Contraindications of albendazole:

• Known hypersensitivity to the drug

• Pregnancy

• Cirrhosis of liver

• Children younger than 2 years of age.

❗❗Dose of albendazole :

• Usual dose(ascariasis, trichuriasis, hook worm infestation) : 400 mg tablet, single dose

• In hydatid cyst : 400 mg 12 hourly with meal for 1 month or longer

Albendazole is administered on an empty stomach when used against intraluminal parasites. Albendazole is administered with a fatty meal when used against tissue parasites

☑☑Dose of mebendazole :

• Usual dose(ascariasis, trichuriasis, hookworm infestation) : 100 mg tablet, 1 tablet 12 hourly, for 3 days.

👉Mechanism of action of pyrantel pamoate

It causes activation of nicotinic receptors

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Resulting in persistent depolarization

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Spastic type of paralysis

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Expulsion of worms.

## Anti-amoebic drugs: These drugs are useful in infection caused by the anaerobic protozia Entamoeba histolytica. Amoebiasis is caused by Entamoeba histolytica.

• Bowel lumen amoebiasis is asymptomatic and trophozoites (non infective) and cysts(infective) are passed into the feces.

• Tissue invading amoebiasis gives rise to dysentery, hepatic amoebiasis and liver abscess.

👉Mechanism of action of metronidazole:

Enters into anaerobic bacteria and sensitive protozoans

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The nitro group of metronidazole is chemically reduced by accepting electron

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Reduced cytotoxic compounds of metronidazole bind with proteins and DNA

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Cell death

✅ Uses of metronidazole :

• Amoebiasis : Metronidazole is the first line drug for all forms of amoebic infection.

• For invasive dysentery and liver abscess – 800 mg TDS for 7-30 days

• Giardiasis : Highly effective in a dose of 400 mg TDS for 7 days

• Trichomonas vaginitis : It is the drug of choice

• Anaerobic bacterial infections : After colorectal or pelvic surgery, appendicectomy etc.

• Pseudomembranous enterocolitis.

❗❗Adverse effects of metronidazole :

Relatively frequent and unpleasant, but mostly non serious –

• Metallic taste and abdominal cramps, anorexia, nausea are the most common

• Looseness of stool is occasional.

• Less frequent side effects are- headache, glossitis, dryness of mouth and dizziness.

• Urticaria, flushing, itching and fixed drug eruption occur in allergic subjects.

❎❎ Contraindications of metronidazole :

• Pregnant women

• Lactating mother

• Young children

• Liver insufficiency