This document discusses various anthelmintic drugs used to treat different types of helminth (worm) infections. It provides details on the classification, mechanisms of action, pharmacokinetics, efficacy, dosing and side effects of common anthelmintics including mebendazole, albendazole, piperazine, levamisole, niclosamide and others. Mebendazole and albendazole are broad spectrum benzimidazole derivatives that are effective against roundworms, hookworms, whipworms and some tapeworms. Piperazine is highly active against ascariasis but less so for other helminths. Levamisole and tetramisole help exp

1. Anthelmintics

2. Introduction
• Anti – against and helminths – worms
• May be
 Vermicide – Drugs that kill worms
 Vermifuge – expel infesting helminths
 Peristaltic movement of Intestine
 Cathartic and purgative action
 Ideal anthelmintics:
 Orally effective
 Effective in single dose
 Inexpensive
 Wide safety of margin with highest toxicity to worms, but lesser toxic to the host

3. Common Helminths
• Roundworm: Ascaris lumbricoides
• Hookworm: Ancylostoma duodenale and Necater
americanus
• Threadworm: Enterobius vermicularis and
Strongyloides stercoralis
• Whipworm: Trichuris trichiuria and Trichinella spiralis
• Filaria: W. Bancrofti, Brugia malayi
• Tapeworms: T. saginata, T. solium, H. nana
• Hydatid disease: E granulosus and E multilocuralis
• Guniea worm: Dracunculus medinensis

4. Available Drugs
1) Mebendazole
2) Albendazole
3) Pyrantel pamoate
4) Piperazine
5) Levamisole and tetramisole
6) Diethyl carbamazine citrate (DEC)
7) Ivermectin
8) Niclosamide
9) Praziquantel

5. Mebendazole
• Synthetic benzimidazole derivative
• Action:
o 100% cure rate for round worm, hook worm, enterobius (less for Strongyloides)
and trichuris (not for tissue Trichinella spiralis)
o 75% effective for tape worms but not for H. nana
o Hadatid cyst: prolonged treatment
o Hatching of nematode eggs and larva inhibited and Ascaris eggs are killed
• MOA:
o Slow in action, takes 2-3 days to develop
o Blocks glucose uptake in the parasite and depletion of glycogen store
o Site of action: microtubular protein ß-tubulin – inhibits polymerization
o Intracellular mictotubules are grdually lost

6. Mebendazole – contd.
• Pharmacokinetics: Minimal absorption, 75-90% is passed
unabsorbed in the faeces. Excreted mainly in urine as inactive
metabolite
• Adverse effects:
o No adverse effects with short term therapy, mild GIT disturbanes-nausea, diarrhoea
and abdominal pain
o Allergic reactions, granulocytopenia, loss of hair and elevation of liver enzymes
o Enzyme inducers and inhibitors
o Pregnancy - ????
• Uses: Available as 100 mg chewable tablet and 100mg/ml
suspension
o Common indications: 100 mg twice daily for 3 days
o Enterobius 100 mg single dose + repeat after 2-3 weeks
o Trichinella spiralis – 200 mg twice daily for 4 days
o Hydatid cyst: 200-400 mg twice daily for 3-4 weeks
Albendazole
preferred

7. Albendazole
• Congener of Mebendazole
• Action: comparable efficacy with mebendazole for round
worm, hook worm and enterobius
o Less effective against trichuris
o But, more effective against strongyloides
o Trichinella effectiveness is almost same
o More effective in tape worm (including H. nana) and hydatid larvae and ova of ascaris
and hook worm
o Weak microfilarial action and cutaneous larva migrans
• Pharmacokinetics: Moderate and inconsistent oral absorption
o Fatty meals enhance absorption
o Fraction absorbed is converted to sulfoxide metabolite – active
o Its active and penetrates brain with t1/2 of 8-9 Hrs – BASIS of TISSUE Anthelmintic
action
o For intesinal worm given in empty stomach and for tissue action – with fatty meals

8. Piperazine
• Highly active drug against Ascaris and Enterobius – but 2nd
choice drug
• Less/not active against hook worms
• MOA:
o Hyperpolarization of Ascaris muscles GABA agonistic action of Cl- channel opening
o Decreased responsiveness to ACh contractile response – flaccid paralysis
o Recover – purgation required
o Does not excite Ascaris for abnormal migration
• ADRs: usually well tolerated - nausea, vomiting
o Dizziness and convulsion in high doses
o Contraindicated in renal insufficiency and epileptics
• Uses: Round worm infestation – 4 gm. once a day for 2 days
o Safe in pregnants
o Used in Intestinal obstruction

9. Levamisole and
Tetramisole
• Effective against any nematodes, but restricted to
Ascriasis and ancylostomiasis
• MOA: 2 mechanisms
o Tonic paralysis of worms and expulsion of live worms - by stimulating ganglia of
worms
o Inhibition of fumerate reductase enzyme: carbohydrate metabolism interfered
• Dose: 50/100/150 mg single dose
o Ascariasis and A. duodenale
o Immunomodulator
o Safe and well tolerated – mass treatment of round worms

10. Niclosamide
• Against tape worms – saginata, solium, latum and nana
• MOA: Inhibition of oxidative phosphorylation in
mitochondria and interference of anaerobic generation of
ATP
o Injured worms are digested or expelled (purgation)
o But, problem with T. solium – dangerous visceral cysticercosis
• Regimen: available as 0.5 gm tabs.
1. 2 gm stat – repeat after 1 Hr and saline purgation
2. 2 gm daily for 5 days in H. nana infestation
• ADRs: well tolerated, no systemic toxicity and can be
given in pregnancy