Antihelmentics

1. ANTHELMINTICS
• Drugs which are used either to kill or expel infecting
helminthes (worms) are known as antihelminthics or
anthelmintics.
• Vermicide: kill helminthes vermifuge: expel helminthes
• Three major groups of helminthes the Nematodes,
Trematodes, and Cestodes infect humans.
• As in all antibiotic regimens, the antihelminthic drugs are
aimed at metabolic targets that are present in the parasite
but are either absent from or have different characteristics
than those of the host.

2. 2

3. Endoparasites
Helminths are divided into two major groups:
Nematodes: cylindrical, nonsegmented
worms commonly called roundworms
Platyhelminthes: flattened worms that are
subdivided into two groups:
Cestodes (tapeworms)
Trematodes (flukes)
AnthelminticsAnthelmintics
Antinematodals
Anticestodals
Antitrematodals

4. Classification
Roundworms
Flatworms
Tapeworms

5. Antihelmintic drugs
Drugs active
against
nematodes
Drugs active
against trematodes
Drugs active against
cestodes
Diethylcarbamazine
Albendazole
Mebendazole
Pyrantel pamoate
Ivermectin
Praziquantel
Metrifonate
oxamnquine
Niclosamide
Praziquantel
Albendazole
mebendazole

6. • Intestinal nematodes includes:
1.enterobius vermicularis (pinworm)
2.ascaris lumbricoides (roundworm)
3.ancyclostoma & necator species (hookworm)
4.strongyloides stercoralis (threadworm)
• Tissue nematodes: onchocerca,filariasis
• Medically important trematodes are:
1.schistosoma species (blood fluke)
2.clonorchis sinesis (liver flukes in southeast Asia)
3.paragonimus westermani ( lung fluke in Asia, India)
• Cestodes (Tapeworms)
1.Beef tapeworm – Taenia saginata
2.Pork tapeworm – Taenia solium
3.Cysticercosis – Taenia solium
4.Fish tapeworm – Diphyllobothrium latum
5.Hydatid disease – Echinococcus granulosus

7. Round worm
threadworm
hookworm
pinworm

8. 8
Ascaris lumbricoids Ancylostoma duodenale
Pinworm (male ,female) Whipworm

9. 9
Tricuris tricura(whip worm)

12. beef tapeworm
Hydatid cyst in liver

16. Infecting organism Drug of choice Alternative drug
Ascaris(roundworm) Albendazole,mebendazole,py
rantel pamoate
piperazine
Ancylostoma(hookworm) Albendazole,mebendazole, pyrantel pamoate
Strongyloids
stercoralis(threadworm
ivermectin Albendazole,mebendaz
ole,
Enterobius
vermicularis(pinworm)
Mebendazole,pyrantel
pamoate
albendazole
filariasis diethylcarbamazine ivermectin
onchocericasis ivermectin --------
Drug for treatment of nematodes

17. Infecting organism Drug of choice Alternative drug
s,.haematobium praziquantel metrifonate
s.mansoni praziquantel oxamniquine
s.japonicum praziquantel
Fasciola hepatica bithional
Fasciolopsis buski Praziquantel or
niclosamide
Drug for treatment of
trematodes

18. Infecting organism Drug of choice Alternative drug
t.Saginata (beef tapeworm) Praziquantel or
niclosamide
mebendazole
t.Solium(pork tapeworm) Praziquantel or
niclosamide
Cysticercosis(pork tapeworm
larval stage)
albendazole praziquantel
Diphyllobothrium latium(fish
tapeworm)
Praziquantel or
niclosamide
Hydatid disease albendazole
Drug for treatment of cestodes

19. •Mebendazole is an benzimidazole with
anthelmintic activity against most nematodes and some
other worms.
•Activity against some larval stages and ova has also been
demonstrated.
Mechanism of Action
•Mebendazole acts by binding to and interfering with the
assembly of the parasites microtubules and also by
decreasing glucose uptake. Affected parasites are expelled
with the feces.

20. Indication
• It is used in the treatment of the intestinal nematode infections:
• ascariasis (roundworm infection)
• enterobiasis (pinworm or threadworm infections)
• hookworm (ancylostomiasis and necatoriasis)
• trichuriasis (whipworm infection)
Contraindication and Precautions
• Contraindicated in patients with hypersensitivity.
• Precaution should be taken by patients with renal or hepatic
impairment.
Adverse effects
• Abdominal pain, nausea, headache, numbness, dizziness, transient
diarrhoea, tinnitus etc.
Dose
• adults and children aged over 2 years 100 mg twice daily for 3 days

21. Albendazole
•Similar to Mebendazole!
•Albendazole is a benzimidazole that inhibits microtubule synthesis
and glucose uptake in nematodes & cestodes (primary).
•Indication
•It is used in in the treatment of the cestode infections:
•cysticercosis (tapeworm infection)
•echinococcosis (hydatid disease)
•Ascariasis, Enterobiasis, Hookworm, strongyloidiasis, giardiasis and
trichuriasis.
Contraindication and Precautions
•Contraindicated in patients with hypersensitivity, liver impairment,
pregnant women and neonates.
•Precaution should be taken by patients with renal impairment and
with anaemia.
Dose: over 2 years– 400 mg and 1-2 years– 200 mg single dose.

23. •Thiabendazole is used for both nematodes
(tissue and some roundworms)
•Thiabendazole is a benzimidazole with anthelminthic
activity against strongyloidiasis caused by
Strongyloides stercoralis, (threadworm), cutaneous
larva migrans, and early stages of trichinosis (caused by
Trichinella spiralis,
•Thiabendazole, like the other benzimidazoles, affects
microtubular aggregation.
•A common regimen for therapy of strongyloidiasis is 25
mg/kg of thiabendazole given twice daily after meals
for 2 days.
•The adverse effects most often encountered are
dizziness, anorexia, nausea, and vomiting.
•Its use is contraindicated during pregnancy.

24. •Pyrantel Pamoate is a broad-spectrum anthelmintic
highly effective for the treatment of various species of worms.
Mechanism of Action
• It acts as a depolarizing, neuromuscular-blocking agent, causing
persistent activation of the parasite's nicotinic receptors.
• The paralyzed worm is then expelled from the host's intestinal tract.
Indication
• Used in the treatment of pinworm, ascariasis, and Trichostrongylus
orientalis infections.
• It is moderately effective against both species of hookworm.
Contraindication and Precaution
• Contraindicated in patients with hypersensitivity.
• Precaution by patients with liver dysfunction and anaemia.
Adverse effects
• Adverse effects are mild and include headache, nausea, vomiting,
and diarrhea.
Dose
• 10-15mg/kg at bed time

25. •Niclosamide is an anthelminthic which is active against
most tapeworms.
• It was the drug of choice for tapeworm infections but has now
largely been superseded by Praziquantel.
Mechanism of Action
• Adult worms (but not ova) are rapidly killed due to inhibition of
oxidative phosphorylation or stimulation of ATPase activity,
resulting in energy depletion.
Indication
• It is used for the treatment of tapeworm and intestinal fluke
infections.
• A laxative is administered prior to oral administration of
niclosamide. This is done to purge the bowel of all dead segments
and so preclude digestion and liberation of the ova.

26. Contraindication and Precautions
• Contraindicated in patients with hypersensitivity.
• Precaution should be taken by patients with renal or hepatic
impairment.
Adverse Effects
• Vomiting, Nausea, Dizziness, Stomach pain, Etching, Headache etc.
Dose
• Adult: 2 gm as a single dose after a light breakfast.
• Child: <2 yrs– 500mg; 2-6 yrs– 1gm

27. •Praziquantel is an anthelmintic with a broad
spectrum of activity against trematodes (flukes) including
all species of Schistosoma pathogenic to man, and against
cestodes (tapeworms).
Mechanism of Action
•Praziquantel rapidly inters the cell membrane of worm
leading to increased calcium concentration.
•The high concentration of calcium may cause contracture
and paralysis of the parasite, which will be completely
destroyed in intestine or excreted in stool.
Contraindication and Precautions
•Contraindicated in patients with hypersensitivity.
•Precaution should be taken by patients with severe hepatic
disease.

28. Indication
•It is used in the treatment of schistosomiasis, taeniasis,
and intestinal, liver, and lung fluke infections.
•The drug's safety and effectiveness as a single oral dose
have also made it useful in mass treatment of several
infections.
Adverse Effects
•Common side effects are headache, diarrhoea, dizziness,
drowsiness, malaise, abdominal discomfort, nausea, and
vomiting
•Hypersensitivity reactions such as fever, urticaria, pruritic
skin rashes, and eosinophilia can also occur.
Dose
•Adult and child >4 yrs: 3 doses of 20mg/kg every 4-6 hours
or 40-60mg/kg as a single dose.
•Child: below 4 yrs are not recommended.

29. •Diethylcarbamazine (DEC)
•MOA: Used in the treatment of filariasis because of its ability to
immobilize microfilariae and render them susceptible to host defense
mechanisms.
• Combined with albendazole, diethylcarbamazine is effective in the
treatment of Wuchereria bancrofti and Brugia malayi infections.
• Indication
• It is used in the treatment of lymphatic filariasis, toxocariasis (visceral
larva migrans) and loiasis disease (filarial nematode infection).
• Adverse effects are primarily caused by host reactions to the killed
organisms. Symptoms include fever, malaise, rash, myalgias, arthralgias,
and headache, and their severity is related to parasite load. Most patients
have leukocytosis. Antihistamines or steroids may be given to ameliorate
many of the symptoms.
Contraindication and Precautions
• Contraindicated in patients with hypersensitivity and cardiovascular
disorders.
• Precaution should be taken by patients with renal or hepatic impairment.
Dose
• Adult: 1-6 mg/kg daily for 3 days, for 3 week
• Child: 1-2 mg/kg

31. •Ivermectin is the drug of choice for the treatment of
onchocerciasis (river blindness) caused by Onchocerca volvulus
and for cutaneous larva migrans and strongyloidiasis.
• MOA: Ivermectin targets the parasite’s glutamate-gated
chloride channel receptors. Chloride influx is enhanced, and
hyperpolarization occurs, resulting in paralysis of the worm.
The drug is given orally. It does not cross the blood-brain
barrier and has no pharmacologic effects in the CNS.
• Uses:
• Drug of choice in treatment of onchocercosis, and
threadworm infection
• Adverse effect
• The killing of the microfilaria can result in a Mazotti-like
reaction (fever, headache, dizziness, somnolence, and
hypotension).
• Contraindication
• patients with meningitis, because their blood-brain barrier is
more permeable, making CNS effects possible.
• Ivermectin is also contraindicated in pregnancy.

32. •Piperazine
•MOA: causes paralysis of worm by blocking acetylcholine
at myoneural junction ,expelling the live worm by normal
peristalsis.
•Indications:
•Used for the treatment of ascariasis/ enterobiasis.
•Not recommended for other helminth infections
Dose: For Ascariasis
•Adult: 75 mg /kg/day once for 2 days
•Children: 75 mg/ yr
•Treatment is continued for 3-4 days or repeated after
one week in case of heavy infections.
For Enterobiasis: 50 mg /kg once a day for 7 days OR
75 mg single dose repeated after 3 wks

33. Adverse effects:
• GI disturbance
• Neurotoxicity ,allergic reactions serum sickness like syndrome
Contraindications
• Epilepsy
• Impaired liver or kidney functions
• pregnancy
• Malnutrition

34. • LEVAMISOLE
•MOA: The ganglia in worms are stimulated causing tonic
paralysis and expulsion of live worms. Interference with
carbohydrate metabolism (inhibition of fumarate
reductase) may also be contributing.
•Dose: Ascariasis—Single dose 150 for adults, 100 mg for
children 20–39 kg body weight, 50 mg for 10–19 kg.
•Adverse effects: One or two doses used in helminthiasis
are well tolerated.
•Incidence of side effects—nausea, abdominal pain,
giddiness, fatigue, drowsiness or insomnia is low.

35. • BITHIONOL is drug of choice for the treatment of fasioliasis ( sheep liver
fluke)
• It is also alternative drug for pulmonary paragonimiasis
• Clinical uses:
• 30-50 mg /kg in 2-3 divided doses administered orally after meals on alternate
day for 10 – 15 days.
• Adverse effects:
GI disturbance
Dizziness,headache
Pruriuts ,urticaria,Leucopenia
• Contraindications and precautions:
hepatitis ,leucopenia
Used with caution under 8 years of age.