Helminths are parasitic worms that infect humans. The major types are nematodes (roundworms and pinworms), trematodes (flukes), and cestodes (tapeworms). Antihelminthic drugs work by killing the worms or causing them to be expelled. Common antihelminthics include mebendazole, albendazole, pyrantel pamoate, piperazine, diethylcarbamazine, ivermectin, niclosamide, and praziquantel. They have different mechanisms of action and are used to treat different specific helminth infections. Albendazole and praziquantel are often used as first-line treatments

1. Antihelminthics
Dr. Kaushik Mukhopadhyay
Dept. of Pharmacology
ESI PGIMSR & ESIC Medical College, Joka

2. Relative
incidence
of helminth
infections
worldwide

3. Helminths are macroscopic, multiceullar organism
having their own digestive system, excretory,
reproductive and nervous systems.
Helminths
NEMATHELMINTHS PLATYHELMINTHS
TREMATODES CESTODES

4. Nematodes
 Long, round bodies, unsegmented worms, tapered at both
ends.
 Most found primarily in intestine.
 Attached to the mucosa and feed host blood and tissue fluid.
 EX:
Ascaris lumbricoides (roundworm),
Trichuris trichiura (whipworm),
Enterobius vermicularis (pinworm),
Ancylostoma duodenale & Necator americanes
(hookworms)
Enterobius vermicularis(Pin worm)
Wuchereria bacncrofti (Filarias)
(Nemathelminths)

5. Platyhelminths
Trematodes (Flukes)
Ex:-
Blood flukes ( Schistosomiasis)
Liver flukes (Clonorchiasis)
Lung Flukes (Paragonimiasis)
Intestinal flukes(Fasciolopsiasis)
Cestodes( Tape worm)
Ex:-
Beef tape worm (Taenia saginata)
Pork tape warm (Taenia solium)
Fish tape worm (Diphyllobothrum latum)
Dwarf tape warm (Hymenolepis nana)

6. ROUND WORM Hookworm
filariasis Pin worm male, female

7. Tapeworm whipworm
Onchocerciasis Fasiola hepatica

8. Antihelminthic Drugs

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

10. Available Drugs
1) Benzimidazoles – Mebendazole, Albendazole
2) Pyrantel pamoate
3) Piperazine
4) Levamisole
5) Diethyl carbamazine citrate (DEC)
6) Ivermectin
7) Niclosamide
8) Praziquantel

11. Mebendazole
 Synthetic benzimidazole derivative
 MOA:
inhibition of microtubule polymerization by binding to “ß-
tubulin”
A range of other biochemical changes are found in
nematodes following BZ exposure, including
inhibition of mitochondrial fumarate reductase,
reduced glucose transport,
and uncoupling of oxidative phosphorylation,

12. Mebendazole – contd.
 Pharmacokinetics: Minimal absorption, 75-90% is passed
unabsorbed in the faeces. Excreted mainly in urine as inactive
metabolite
 Adverse effects:
No adverse effects with short term therapy, mild GIT
disturbanes- nausea, diarrhoea and abdominal pain
Allergic reactions, granulocytopenia, loss of hair and
elevation of liver enzymes
 Uses: Common indications: 100 mg twice daily for 3 days
Enterobius 100 mg single dose + repeat after 2-3 weeks
Trichinella spiralis – 200 mg twice daily for 4 days

13. Albendazole
 Congener of Mebendazole
 Pharmacokinetics: Moderate and inconsistent oral
absorption
Fatty meals enhance absorption
Fraction absorbed is converted to “sulfoxide”
metabolite – active
It is active and penetrates brain with t1/2 of 8-9 Hrs –
BASIS of TISSUE Anthelmintic action
For intesinal worm given in empty stomach and for
tissue action – with fatty meals

14. Albendazole – Uses and dosage
 Available as 400 mg tablet and 200 mg/5ml susp.
Normal dosing: Single dose of 400 mg (200 mg below 2
years).
Tape worm: 400 mg for 3 days
Neurocysticercosis: treatment of choice – 400 mg twice
daily for 8-30 days
Hydatid disease: 400 mg BD for 1-6 months (for children,
15 mg/kg per day with a maximum of 800 mg)
Filariasis: with DEC or Ivermectin – in lymphatic filariasis
Used in mass programmes – yearly dose for
microfilaraemia transmission

15. Pyrantel pamoate
 Originally for thread worm but extended to hook worm and round
worms
 MOA:
 Activation of nicotinic cholinergic receptors
 Persistent depolarization leding to contracture and spastic
paralysis – expelling of worms
 Piperazine causes flaccid paralysis – antagonizing action
 Pharmacokinetics: Only 10-15% is absorbed
 ADRs: free from ADRs – mild GIT symptoms, tasteless, non-irritant and
abnormal migration to tissues is not provoked
 Dose and Uses: 250 mg tabs and 50 mg/ml susp.
 Used in Ascaris, entarobius and ancylostoma – single dose

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

17. Diethyl carbamazine citrate (DEC)
 Drug of choice for the treatment of filariasis, loiasis
 Pharmacokinetics:
 Rapidly absorbed from gut
 It is excreted in urine unchanged
 MOA: 2 mechanisms
 Alteration of Mf membrane – to be readily phagocytosed by tissue
monocytes
 DEC compromises intracellular processing and transport of certain
macromolecules to the plasma membrane
 Uses: Filariasis: 2 mg/kg tds X 7 days – improved
Elephantiasis not affected
 Tropical eosinophilia (2-4 mg/kg tds for 2-3 weeks)
 ADRs: Nausea, vomiting, loss of appetite etc.
 Febrile condition – rash, pruritus, enlargement of lymph nodes

18. Levamisole and Tetramisole
 Effective against any nematodes, but restricted to Ascriasis and
ancylostomiasis
 MOA: 2 mechanisms
 Tonic paralysis of worms and expulsion of live worms - by
stimulating ganglia of worms
 Inhibition of fumerate reductase enzyme: carbohydrate
metabolism interfered
 Dose:
 Ascariasis and A. duodenale
 Immunomodulator
 Safe and well tolerated – mass treatment of round worms

19. Ivermectin
 Obtained from Streptomyces avermitilis
 Action:
 Drug of choice for Onchocercosis volvulus and Strongyloides
and equal to DEC in Filaria
 Also efective against ascariasis, scabies and head lice
 MOA:
 Acts via special type of glutamate gated Cl- channel found only
in invertebrates
 Such channels are absent in man, flukes and tape worms – not
effective
 Potentiation of GABA activity – paralysis of muscles of worms

20.  Pharmacokinetics: absorbed well orally, widely distributed but not in
CNS, long half-life – 48 to 60 Hrs
 Uses: 3/6 mg tablets
 Filaria: single dose 0.2 mg per kg with 400 mg Albendazole
annually for 5-6 years
 Strongyloides: 0.2 mg/kg single dose
 Replaced DEC in O. volvulous by WHO
 ADRs: Pruritus, nausea, abdominal pain and sudden ECG changes
Ivermectin…contd

21. Niclosamide
 Against tape worms – saginata, solium, latum and nana
 MOA: Inhibition of oxidative phosphorylation in
mitochondria and interference of anaerobic generation
of ATP
Injured worms are digested or expelled (purgation)
But, problem with T. solium – dangerous visceral
cysticercosis
 Regimen:
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

22. Praziquantel
 Novel anthelmintic with wide range of action
 Action: Mainly on Trematodes, cestodes but not nematodes
 MOA:
 Rapidly taken up by worms
 At the lowest effective concentrations, it causes increased
muscular activity, followed by contraction and spastic paralysis
(influx of intracellular Ca++ ).
 At slightly higher concentrations, praziquantel causes
tegumental damage and exposes a number of tegumental
antigens
Pharmacokinetics: Rapidly absorbed and enhanced by food
 High first pass metabolism
 Phenytoin, carbamazepine and steroids induce metabolism –
failure of therapy

23. Praziquantel – contd.
 ADRs: Bitter in taste, produce nausea and vomiting and
abdominal pain
Headache, dizziness and sedation
Urticaria, rash, fever etc- destroyred flukes
 Uses: available as 500 mg/600 mg tabs
First line of drug in all tape worms except
Neurocysticercosis (10-25 mg/kg per day single dose)
First line of drug in all schistosome infestations and
flukes except Fasciola hepatica (50-75 mg/kg/day)

24. Drug of Choice
Albendazole is DOC of all nematodes except –
Enterobiasis (Mebendazole)
Wuchereria & brugia (DEC)
Oncocerca & Strongyloides (ivermectin)
Dracunculus (Metronidazole)

25. Drug of Choice
Praziquantel is DOC of all trematodes &
cystodes except –
Fasciola hepatica (Bithionol)
Hydatid disease (Albendazole)

26. Thank You