The current presentation includes the pharmacology of different drugs used for the treatment of nematode, trematode and cestode infections. Reference: Essentials of Medical Pharmacology, K D Tripathi, Sixth Edition

1. ANTHELMINTICS
Anusha Shaji, B.Pharm, M.Pharm
Assistant Professor
Department of Pharmacology
Nirmala College of Pharmacy,
Muvattupuzha, Ernakulam

2. Anthelmintics
Anthelmintics are drugs that either kill (vermicide) or expel
(vermifuge) infesting helminths.
Three major groups of helminths (worms) infect humans.
Nematodes
Trematod, and
Cestodes
Helminthiasis is rarely fatal, but is a major cause of ill
health.

4. Classification

5. Drugs For The Treatment Of Nematodes
Nematodes are elongated roundworms that possess a
complete digestive system, including both a mouth and an
anus.
They cause infections of the intestine as well as the blood
and tissues.
Mebendazole
Mebendazole, a synthetic benzimidazole compound
Effective against a wide spectrum of nematodes.
It is a drug of choice in the treatment of infections by
whipworm, pinworm , hookworms, and roundworm.

6. Whipworm- Trichuris trichiura
Pinworm- Enterobius vermicularis
Hookworms- Necator americanus and Ancylostoma
duodenale
Roundworm- Ascaris lumbricoides
Mechanism
It acts probably by blocking glucose uptake in the parasite
and depletion of its glycogen stores.
↓
Intracellular microtubules in the cells of the worm are
gradually lost.
↓

7. The site of action of mebendazole appears to be the
microtubular protein ‘β-tubulin’ of the parasite.
↓
It binds to β-tubulin of susceptible worms with high affinity
and inhibits its polymerization.
↓
Hatching of nematode eggs and their larvae are
also inhibited.
↓
Ascaris ova are killed.

8. Pharmacokinetics
Absorption of mebendazole from intestines is minimal
75–90% of an oral dose is passed in the faeces.
The fraction absorbed is excreted mainly as inactive
metabolites in urine/ faeces.
Adverse effects
Diarrhoea, nausea and abdominal pain have attended its use
in heavy infestation.
Incidents of expulsion of Ascaris from mouth or nose have
occurred, probably due to starvation of the parasite and their
slow death.
Allergic reactions, loss of hair and granulocytopenia have
been reported with high doses.

9. Drugs For The Treatment Of Trematodes
The trematodes (flukes) are leaf-shaped flatworms that are
generally characterized by the tissues they infect.
↓
They may be categorized as liver, lung, intestinal, or blood
flukes
Praziquantel
Trematode infections are generally treated with
praziquantel
This novel anthelmintic has wide ranging activity against
Schistosomes, other trematodes, cestodes and their larval
forms but not nematodes.

10. MOA: Permeability of the cell membrane to calcium is
increased, causing contracture and paralysis of the parasite.
Praziquantel is rapidly absorbed after oral administration
and distributes into the cerebrospinal fluid.
High levels occur in bile.
The drug is extensively metabolized oxidatively, resulting in
a short half-life.
The metabolites are inactive and are excreted through urine
and bile.
Adverse effects include drowsiness, dizziness, malaise,
and anorexia as well as gastrointestinal upsets.
The drug is not recommended for pregnant women or
nursing mothers.

11. Drug interactions
Due to increased metabolism have been reported with
dexamethasone, phenytoin, and carbamazepine.
Cimetidine, which inhibits cytochrome P450 isozymes
causes increased praziquantel levels.
Praziquantel is contraindicated for the treatment of ocular
cysticercosis → because destruction of the organism in the
eye may damage the organ.
Uses
Tapeworms
Neurocysticercosis
Schistosomes
Other flukes

12. Drugs For The Treatment Of Cestodes
The cestodes, or “true tapeworms,” typically have a flat,
segmented body and attach to the host’s intestine
Like the trematodes, the tapeworms lack a mouth and a
digestive tract throughout their life cycle.
Albendazole
Albendazole is a benzimidazole
MOA: Inhibits microtubule synthesis and glucose uptake
in nematodes.
Its primary therapeutic application, however, is in the
treatment of cestodal infestations, such as cysticercosis
(caused by Taenia solium larvae) and hydatid disease
(caused by Echinococcus granulosus).

13. Albendazole is erratically absorbed after oral
administration, but absorption is enhanced by a high-fat
meal.
It undergoes extensive first-pass metabolism, including
formation of the sulfoxide, which is also active.
Albendazole and its metabolites are primarily excreted in
urine.
Adverse effects
Headache and nausea.
Treatment of hydatid disease (3 months) has a risk of
hepatotoxicity and, rarely, agranulocytosis or pancytopenia.

14. NEMATODE INFECTIONS SUMMARY

16. TREMATODE INFECTIONS SUMMARY

17. CESTODE INFECTIONS SUMMARY

18. Summary