Antihelmintics Pharmacology Amity Institute Of Pharmacy

1. Antihelmintics
Pharmacology
Amity Institute Of Pharmacy
Priyanshu Ranjan Avinash Kumar Gupta Sanjeev Kumar Singh

2. Antihelmintics are drugs used to treat infections caused by parasitic worms
Act by various mechanisms –
May paralyse the worms
Some act by killing the adult & larval forms
Preventing their further growth by impairing egg formation
Overview

3. Helminthes

4. Benzimidazoles
Mebendazole, Albendazole, Thiabendazole
Vinyl Pyrimidines
Pyrantel Pamoate, Oxantel
Piperazine Derivatives
Diethylcarbamazine citrate, Piperazine citrate
Quinoline & Isoquinolines
Praziquantel, Oxamniquine
Classification

5. • Mebendazole is a synthetic benzimidazole that has a wide spectrum of anthelmintic
activity and a low incidence of adverse effects.
• It is a drug of choice in treating infections by whipworm, pinworm, hookworms &
roundworm.
• Mechanism of action: – Acts by inhibiting microtubule synthesis. Its bind with
parasites’ ‘β-tubulin’ & inhibit its polymerization.
In addition mebendazole probably blocks glucose uptake in parasite and depletes its
glycogen stores.
• Efficacy of the drug varies with –
Gastrointestinal transit time
Intensity of infection
Mebendazole

7. •Absorption of mebendazole from intestines is minimal
•Less than 10% of orally administered mebendazole is absorbed
•Half-life of 2-6 hours
•75 – 90% of oral dose passed in the faeces
•Dose:
– 100 mg chewable tablet
– 100 mg/5ml suspension
Pharmacokinetics

8. •It is generally administered in a dose of 100 mg for 2-3 weeks in condition
of enterobiasis.
•It is used to treat infections by Trichinella spiralis in a dose of 200 mg
every 12 hours (b.i.d) for four days.
•It is used to treat infections of visceral larva migrans.
Therapeutic Uses 💊

9. Adverse Effects
Mild Nausea
Diarrhoea
Vomitting
Abdominal pain
Pregnancy –
shown to be embryotoxic &
teratogenic in experimental
animals
Contraindications

10. • Structurally similar to mebendazole but relatively more effective
• Regarded as congener of mebendazole
• Has broad spectrum activity & active against all forms of parasitic worms
including roundworm, hookworm, whipworm & threadworms
• Mechanism of action –Acts by selectively and irreversibly inhibiting or blocking
the uptake of glucose and other nutrients & depleting glycogen storage
• Inhibiting microtubule formation by binding to microtubular protein of the
parasitic worms is another mechanism of action
Albendazole

12. •Used in the treatment of ascariasis, enterobiasis and hookworm infection
•Excellent drug for cysticercosis of muscles
•Treating Trichinosis
•Treating capillariasis
•Hydatid disease or echinococcosis
Therapeutic Uses 💊

14. • Pyrimidine derivative
• Has broad spectrum Anthelmintic activity
• Mechanism of action – Acts by activating nicotinic receptors that cause
release of acetylcholine and inhibition of cholinesterase at the NMJ of
helminthes & results in their spastic paralysis. Hence, helminthes are unable to
maintain their position in the intestinal lumen and are expelled from the body
Pyrantel Pamoate

15. •Used to cure enterobiasis and ascariasis (Dose – 11 mg per kg
orally)
•Combination of pyrantel & oxantel is effective
•Also effective against hookworm infections
Therapeutic Uses
Adverse Effects
GI manifestations – nausea, vomiting, diarrhoea, anorexia, etc
Other – Dizziness, insomnia, headache
💊

16. MOA - Piperazine causes hyperpolarization of Ascaris muscle by GABA
agonist action (opening of chloride channels leads to relaxation and decresses
responsiveness to contractile action of Ach)
• Orally active and partly metabolized in liver and excreted in urine.
• ADR: Its safe and well tolerated. Dizziness and excitement occur at high
doses. Toxic dose produce convulsion and death, due to respiratory failure.
• Contraindicated in renal insufficiency & epileptics
•Safe in pregnancy
Piperazine

18. • DEC developed in 1948 - first drug for filariasis.
• Absorbed after oral ingestion, well distributed, metabolized in liver
•Excretion is faster in acidic urine.
• Plasma t½ is around 2-10 hours
•DEC has a highly selective effect on microfilariae (Mf)
• Action of DEC appears to be alteration of Mf membranes so that they are
readily phagocytosed by tissue fixed monocytes, but not by circulating
phagocytes.
Diethyl carbamazine citrate (DEC)

19. THERAPEUTIC USES
Treating filariasis, tropical eosinophilia, Loa loa & O. vovulus infection
ADVERSE EFFECTS
•Nausea
•Loss of appetite
•Headache
•General weakness
•Dizziness

21. Thank You