anthelmintic drugs. helmintic infections human is the primary host for most helminthic infections. ...
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Anthelmintic Drugs
Helmintic infections
Helmintic infections
Human is the primary host for most helminthic infections.
Most worms produce eggs and larva
These pass out of human body and infect secondary host
Immature forms invade humans via skin or GIT
Types of worms
Worms live in host,s alimentary canal
Worms or larvae live in muscles , viscera , menninges, lungs. Subcutaneous tissues
Intestinal Worms
A) Round worms ( Nematodes )
Ascaris lmubricods ( common ) Enterobius vermicularis ( pin worm) Trichris trichuria ( whip worm) Strongyloids stercoralis ( thread Ankylostoma dudenale ( hook worm
B) Tape worms ( cestodes )
Taenia saginata ( Beef) Taenia solium ( pork) Humans become infected by eating
raw or unde cooked meat containing larvae of infected cattle or pig
Continue ( cestodes )
In some cases the larva gets encysted in muscles , viscera , brain , eye resulting in cysticercosis
Tissue worms
Filariae ( bancrofti, loa loa ) Adult filariae live in the lymphatics ,
causing lymphadenitis , swelling of limb. Microfilariae goes to blood stream to be ingested by mosquitoes
Trichnella spiralis : larva migrats from intestine to tissues of leg or foot producing ulcer
Anthelminthic Drugs
May act by causing : paralysis of the worm. damaging the worm leading to partial digestion or
rejection by immune mechanisms. interfere with the metabolism of the worm.
Ascaris lumbricoids ( common round worm)
filariasis
Hookworm
Pinworm male ,female
Tapeworm
whipworm
Dircrocoelium dendriticum
Fasiola hepatica
Tricuris tricura
Trichinela spiralis
elephantiasis
Hydateid cyct
cysticercosis
ANTHELMINTIC DRUGS
ALBENDAZOLE Broad spectrum Drug of choice for treatment of hydatid
disease and cysticercosis. Used for the treatment of ( intestinal
nematodes ) e.g. ascariasis , tricurasis and strongyloidiasis, pinworm, hookworm
Mechanism Of Action
Inhibits microtubule synthesis that irreversibly impairs glucose uptake , intestinal parasites are immobilized and die slowly.
larvicidal in : hydatid ,cysticercosis , ascariasis and hook worm infections.
Ovicidal in ascariasis ,hookworm , trichuriasis
Pharmacokinetics
Benzimidazole carbamate
Administered orally , absorption increased with a fatty meal
Metabolized in the liver to the active metabolite albendazole sulfoxide
Pharmacokinetics
Plasma half life 8-12 hours sulfoxide is mostly protein bound
distributes well to tissues and enters bile, CSF & hydatid cysts.
Metabolites are excreted in urine
Clinical uses
Used on empty stomach when used against intraluminal parasites but with a fatty meal when used against tissue parasites.
In ascariasis ,trichuriasis ,hookworm, pin worm infections : children over 2 years & adults (single dose 400mg, repeated for 2-3 day in heavy ascaris infection . For 2 wks for pin worm infection
2. Hydatid diseases
Albendazole (con’)
3. Neurocysticercosis: Used with corticosteroid to decrease the
inflammation caused by dying organism and it also reduces the duration of course for 21 days
4. Other infections: Drug of choice in cutaneous and visceral larva migrans , intestinal capillariasis & others
Adverse Effects
In short term(1-3 days): No significant adverse
effects
In long term use : abdominal pain, headache ,fever ,fatigue, alopecia ,
increased liver enzymes , pancytopenia. Not given during pregnancy, hypersensitive peoples &
children under 2 years .
MEBENDAZOLE (Vermox)
Synthetic benzimidazole Wide spectrum and safer than albendazole
Mechanism of action:
As albendazole
It kills hookworm, pin worm , ascariasis and trichuris eggs.
Pharmacokinetics
less than 10% of orally administered drug is absorbed
Absorption increases with fatty meal. Absorbed drug is 90 % protein bound Converted to inactive metabolites . Half- life of 2-6 hours Excreted in urine .
Clinical Uses
Tablets should be chewed before swallowing.
Pinworm , trichuriasis, hookworm & ascaris infections.
in adults and children over 2 years cure rate is 90-100 % except hookworm it is less.
Adverse Effects & Precautions
Short term therapy.Mild GI disturbance.
High dose : hypersensitivity reactions, agranulocytosis , alopecia ,elevation of liver enzymes .
Used with caution under 2ys of age may cause convulsion. Contraindicated in pregnancy.
.
Thiabendazole Mechanism as other benzimidazole
Chelating agent and form stable complexes with metals including iron, but does not bind with calcium.
Rapidly absorbed
Half- life of 1-2 hrs
Completely metabolized in liver and 90% is excreted in urine
Can also absorbed through skin
Clinical uses
Should be given after meals .and tablets should be chewed
Strongyloidal infections In cutaneous larva migrans .Thiabendazole cream
is applied topically or drug can be given orally for 2 days.
Adverse Effects & Contraindications
More toxic than other benzamidazoles GI disturbances Pruritus ,headache, drowsiness ,
psychoneurotic symptoms. Irreversible liver failure. Fatal Stevens –Johnson syndrome Not used in young children , pregnancy, hepatic
and renal diseases.
PYRANTEL PAMOATEBroad spectrum Pharmacokinetics: Poorly absorbed orally Half of the drug is excreted unchanged in the feces.Mechanism of action: Neuromuscular blocking drug leads to paralizes of worms
Effective against luminal organisms( mature or immature forms). Not effective against migratory stages in the tissues or
against ova
Clinical uses Pin worm given orally with or without food.
Ascariasis
Hookworm
Adverse Effects
Infrequent mild GI disturbance drowsiness , headache ,insomnia. Rash ,fever
Contraindications Pregnancy Children under 2 years of age
PIPERAZINE Only recommended for the treatment
of ascariasis cure rate 90% for 2 days treatment.
Readily absorbed orally and excreted mostly unchanged in urine
Mechanism of action: Causes paralysis of ascaris by blocking
acetylcholine at myoneural junction , the live worms expelled by normal peristalsis.
Treatment is continued for 3-4 days or repeated after one week in case of heavy infections.
Adverse Effects
GI disturbance Neurotoxicity , allergic reactions .
Contraindications Epilepsy Impaired liver or kidney functions pregnancy
NICLOSAMIDE
Second-line drug for treatment of tape worm infections.
Mechanism of action: Adult worm is rapidly killed by inhibition of
oxidative phosphorylation .
Pharmacokinetics: Poorly absorbed from gut & excreted in urine.
Clinical Uses
Treatment of most forms of tapeworms. Not effective against cysticercosis or hydatic
disease. Given in the morning on empty stomach. Purgative is necessary to purge all dead segments&
prevent liberation of ova.
Adverse effects
Mild ,infrequent and transitory GI disturbance
Alcohol consumption should be avoided
Not indicated in children under 2 years of age or in pregnancy.
DIETHYL CARBAMAZINE
Drug of choice for the treatment of filariasis and tropical eosinophilia.
Pharmacokinetics: Rapidly absorbed from gut Half- life is 2-3 hours The drug should be given after meals It is excreted in urine as unchanged or metabolite. Dosage is reduced in urinary alkalosis and renal
impairment.
Mechanism Of Action
Immobilizes microfilariae and alters their surface structure ,displacing them from tissues & making them susceptible to destruction by host defense mechanism
Adverse Effects
Fever , malaise, papular rash, headache, GI disturbance,cough. Chest,muscle,joint pain
Leucocytosis Retinal hemorrhage Encephalopathy lymphangitis and lymphadenopathy. *It is not teratogenic
Contraindications & Cautions
* Hypertension
* Renal disease
*patient with lymphangitis
Patients suspected of malaria
IVERMECTIN Drug of choice for treatment of filaria &
strongyloidiasis It is a macrocyclic lactone ring Given only orally Rapidly absorbed Does not cross BBB. Half- life is 16 hrs Excretion in urine & feces.
Mechanism Of Action
Paralyze nematodes by intensifying GABA- mediated transmission of signals in peripheral nerves.
Clinical uses
Drug of choice for cutaneous larva migrans & strongyloidiasis.
Onchocerciasis
It is also used for scabies , lice . Filariasis ( it is microfilaricidal ).
Adverse Effects
Fatigue ,dizziness, GI disturbance Killing of microfilaria result in a Mazotti
reaction ( fever, headache, dizziness, somnolence, hypotension , tachycardia, peripheral edema……).
Corneal opacities & other eye lesions.
Contraindications & Cautions
Concomitant use with other drugs that enhance GABA
e.g Barbiturates, bnzodiazepines, valproic acid. pregnancy Meningitis Children under 5 years of age.
BITHIONOL
Drug of choice for the treatment of fascioliasis ( sheep liver fluke)
Pharmacokinetics: It is orally administered and excreted in urine.
Adverse Effects
GI disturbance Dizziness, headache Skin rashes , urticaria, Leucopenia
Contraindications and precautions: Hepatitis , leucopenia Used with caution in children under 8 years
of age.