drugs used against parasites by Dr. Maria Qammar

1. Dr. Maria Qammar
Assistant Professor
M-Phil (Pharmacology)
ANTI HELMINTHIC DRUGS

2. Helminths??
 Parasitic worms
 Multicellular organisms
 Feed on a living host to gain nourishment and
protection, while causing poor nutrient absorption
and disease in the host.

3. Groups:
 Nematodes:
 Round worm (Ascaris lumbricoides)
 Hook worm (Necator americanus, ancylostoma
deudenale)
 Pin worm (Entrobius vermicularis)
 Thread worm (Strongyloides stercoralis)
 Filarial worm ( Wuchreria bancrofti, Brugia malayi,
Onchocerca volvulus)
 Whip worm (Trichuris trichura)
 Trichinea worm ( Trichinella spiralis)
 Guinea worm (Dracunculus medinensis)

6. Groups…
 Trematodes:
 Blood fluke (Schistosoma hematobium, S. mansoni,
S. japonicum)
 Lung fluke (Paragonimus westermani)
 Liver Fluke (Faciola hepatica)
 Cestodes:
 Pork tapeworm (Taenia solium)
 Beef tapeworm (Taenia saginata)
 Fish tapeworm (Diphyllobothrium latum)
 Dog tapeworm ( Echinococcus granulosus)

9. Classification According To Action on
Parasite

10. Classification Based On MOA:
Based on mechanism of action, these drugs may be
classified as:
1) Drugs inhibiting polymerization of beta tubulin:
Albendazole, mebendazole, thiabendazole,
triclabendazole.
2) Drugs causing spastic paralysis (NN receptor agonist):
Pyrantal pamoate, levamisole
3) Drugs causing flaccid paralysis (GABA agonist):
Piperazine, ivermectin.
4) Drugs altering microfilarial membrane and increasing
phagocytosis: Diethylcarbamazine
5) Drugs inhibiting oxidative phosphorylation: Niclosamide,
Bithionil.
6) Drugs inhibiting cholinesterase: Metrifonate
7) Drugs causing influx of calcium: Praziquantal.

11. Albendazole (Important)
 Benzimidazole carbamate
 Drug of choice for treatment of most nematode
infestations.
 Mechanism of Action
Inhibit microtubule synthesis by inhibiting the
polymerization of beta tubulin.

12. Pharmacokinetics
 Absorption: Increase with fatty meal
 Plasma Half life: 8-12 hrs
 Active metabolite – albendazole sulfoxide
 Distributes well to tissues
 Sulfoxide enters bile, CSF, and hydatid cyst
Albendazole cont….

13. Uses:
 Round worm
 Hook worm
 Pin worm
 Whip worm infections
 Hydatid disease (400mg twice daily with meals for
1 month)
 Neurocysticercosis (Taenia solium)
 Cutaneous larval migrans
 Visceral larval migrans
Albendazole cont….

17. Adverse Effects:
 Epigastric distress
 Nausea, vomitting
 Pancytopenia
 Increases liver enzymes
 Headache, dizziness, lassitude
CONTRAINDICATIONS:
 Pregnancy
 Children less than 2 years
Albendazole cont….

18. Mebendazole
 Synthetic benzimidazole
 Similar to albendazole
 Ascariasis (Round worm, pin worm and whip
worm infections)
 GIT disturbances, agranulocytosis and alopecia
 Rarely seizures in chidren under 2 years.
 Teratogenic

19. Thiabendazole
 Chelating agent: binds with iron but does not bind
with calcium.
 Strongyloides, Cutaneous larval migrans

20. Pyrantel Pamoate (UQ)
 Stimulates nicotinic receptor at neuromuscular
junction of nematodes, contraction of muscles
and depolarization induced spastic paralysis.
 Activity only against adult nematodes but not
eggs.
 Not effective against cestodes and trematodes.
 GIT distress, headache and weakness
 Caution against hepatic dysfunction.

21. Ivermectin (UQ)
 Intensify GABA mediated transmission of signals in
the peripheral nerves causing flaccid paralysis.
 Against nematodes microfilariae
 Onchocerciasis
 Strongeloidosis
 Brugia malayi
 Wuchreria bancrofti
 Scabies
 Lice
 Ascariasis
 Cutaneous larval migrans

22. Adverse Effects of Ivermectin
Mazotti Reaction:
They are due to killing action of ivermectin on
microfilariae
 Fatigue, dizziness, nausea, vomitting, abdominal
pain, rashes.
 Fever, tachycardia, hypotension, peripheral edema.
 corneal opacity.
 Controlled by anihistamines and corticosteroids.
 Swelling and abcesses at sites of adult worms
 Avoid with other GABA enhancing drugs: barbiturates,
benzodiazepines and valproic acid
 Avoid in pregnancy and younger children.
Ivermectin cont….

23. Diethylcarbamazine Citrate:
 Immobilizes microfilariae and alters their surface
structure, displacing from tissues and making
them more susceptible to destruction by host
defence mechanism.
 DEC acts on both microfilariae and adult, while
ivermectin acts only in microfilariae. Drug of
choice for filariasis, loaisis and tropical
eosinophilia.

24. Piperazine (Imp)
 Acting as an agonist at GABA receptors causing
flaccid paralysis
 Alternative drug of ascariasis
 Cause GIT disturbances
 Avoid in pregnancy, hepatic and renal
dysfunction, seizure disorders

25. Praziquantel (UQ)
 For cestodes and trematodes except fasciola hepatica and
hydatid disease.
 Cause influx of calcium, causing marked contractility and
then paralysis of cestode and trematode muscles, followed
by vacuolization and parasite death.
 Drug of choice for
 Schistosomiasis (blood fluke)
 Paragonimiasis (lung fluke)
 Clonorchiasis (liver fluke)
 Neurocysticercosis (eggs of Taenia solium) (Pork tapeworm)
 Hydatid disease
 Taenia
 Diphyllobothriasis (uncooked fish infected with
Diphyllobothrium latum)

26. Adverse Effects of Praziquantel
 Headache, dizziness, drowsiness, malaise
 GIT irritation
 Skin rash, fever
 In treatment of neurocysticercosis : increased
intracranial hypertention, seizures.
 Corticosteroids reduces the risk of serious
reaction

27. Bithionil
 Co drug for trematodes
 Co drug of choice for facioliasis and
paragonimiasis
 Cause uncoupling of oxidative phosphorylation.
 Phototoxicity

28. Niclosamide
 Second line drug for cestodes (tape worm).
 Adult worms are rapidly killed due to inhibition of
oxidative phosphorylation or stimulation of
ATPase activity.
 Taenia saginata
 Taenia solium
 Diphyllobothrium latum
 Intestinal fluke infections
 GIT side effects.

29. Metrifonate
 Only active against Schistosoma hematobium.
 Organophosphate prodrug that is converted in the
body to the cholinesterase inhibitor.
 Cholinesterase inhibitor paralyzes adult worms
 Mild cholinergic symptoms are seen: nausea,
vomitting, diarrhea, abdominal pain,
bronchospasm, headache, sweating etc.
 Should not be used after recent exposure to
insecticides or drugs that might potentiate
cholinesterase inhibition.
 Also contraindicated in pregnancy.

30. Oxamniquine
 Alternative to praziquantal for the treatment all
stages of S. mansoni infections.
 Mechanism of action is unknown.
 Dizziness, drowsiness, headache
 Orange to red discolouration of urine, proteinuria,
microscopic hematuria.

31. Doxycycline
 Tetracycline
 W. bancrofti and onchocerciasis (river blindness)