Antihelmintics Drugs

DR.NAZISH

Antihelmintic agents• Drugs for nemtodes :• Diethylcarbamazine• Ivermectin• Mebendazole• Pyrantal pamoate• Thiabendazole• Drugs for trematodes :• Praziquantal , Oxamniquine• Bithionol , Metrifonate• Drugs for cestodes :• Albendazole• Niclosamide

Overview • 3 major groups of helminths(worms) that infects

humans are:• Nematodes (roundworms, whipworm, pinworms,

threadworms ,hookworms)• Trematod (flukes)• Cestodes (tapeworms)

Drugs for treatment of Nematodes • Mebendazole :

• Synthetic benzimidazole compound and wide spectrum antihelminthic, less adverse effects.

• Drug of choice in the treatment of infections by whipworm ,pinworm, hookworms, roundworms.

• Half life 2-6 hours.• Absorption is increased if drug is ingested with fatty meal.• Underoes first pass metabolism and excreted mainly in urine .• The drug acts by inhibiting microtubule synthesis.• Contraindicated in pregnancy.(embryotoxic and teratogenic) and

should b given with caution in cirrhosis and children of 2 years.

• Clinical uses: • Ascariasis(round worms) trichuriasis

(whipworm), hookworms disease(ancylostoma duodenale, nectar americanus), pinworm disease(enterobiasis).

• Adverse effects:• Short term therapy free of side effects.• Mild nausea, vomiting, diarrhea ,abdominal

pain.• High dose therapy--- hypersenstivity

reactions(rash, urticaria, alopecia, agranulocytosis, elevated liver enzymes.)

Pyantal pamoate• Broad spectrum antihelminthic,• Highly effective for Pinworm, Ascariasis and

Trichostrongylus Orientalis infection.• A tetrahydropyrimidine derivative• Poor absorption from GIT• The drug is a neuromuscular blocking agent that causes

release of acetycholine and inhibition of cholinestrase ,this results in paralysis of worms followed by expulsion.

• Adverse effects:are infrequent, mild and transient.• Nausea,vomiting,diarrhea,abdominal

cramps,dizziness,drowsiess,headche,insomnia,rash fever,weakness.

• Caution : in liver dysfunctioning patient

Thiabendazole • A benzimidazole compound .• Rapidly absorbed after ingestion.• Half-life 1.2 hrs.• Completely metabolized in liver and excreted in urine.• Dose should be given after meals.• Adverse effects : dizziness, anorexia, nausea,

vomiting, epigastric pain, abdominal cramps, diarrhea, pruritis, headche, drowziness and neuropsychiatric symptoms,Irreversible liver failure and fatal stevens johnson syndrome.

• Contra : pregnancy or hepatic or renal disease.

Ivermectin • Drug of choice for river blindness and threadworm

infection.• Used orally only in humans and rapidly absorbed.• Half life is about 16 hours. Excretion is through feces.• Drug Targets the parasite’s glutamate-gated chloride

receptors. chloride influx is increased & hyperpolarization occurs, resulting in paralysis of the worms.

• Clinical uses: onchocerciasis, stongyloidiasis, scabies,• Adverse effects: fatigue, dizziness, nausea, vomiting,

abdominal pain ,rashes ,fever ,headche, pruritis, hypotension, tachycardia, lymphadenitis and peripheral edema.

• Contra : pregnancy.

Diethylcarbamazine • Drug of choice in the treatment of filariasis, loiasis,

tropical eosinophilia .• A synthetic piperazine derivative.• Rapidly absorbed from GIT,half life---1-2 hrs if acidic

urine.• Drug should b taken after meals.• Urinary alkalosis and renal impairment may require

dosage reduction.• Clinical uses: Wuchereria Bancrofti, brugia malai.• Adverse effects: fever, rash, mayalgia ,leukocytosis,

anorexia,nausea,vomiting, proteinuria,joint pain,• Caution: hypertension or renal disease.

Drugs for the treament of TrematodesPraziquantal:

• Drug of choice of all forms of schistosomiasis and cysticercosis.• Permeability of the cell membrane is increased,causing contractures

and paralysis of the parasite.• Synthetic isoquinoline pyrazine derivative• Peak serum concentration are reached 1-3 hours after therapeutic

dose.• Half life is 0.8-1.5 hrs• Excretion is mainly via kidneys and bile.• Clinical uses: paragonimasis,taeniasis,neurocuysticercosis,h.nana, hydatid disease.• Contra :ocular cysticercosis.• Drug interaction: phenytoin,carbamazepine, dexamethasone.

Bithionol • Used in treatment of lung fluke( pul.paragonimiasis)

and sheep liver fluke (fascioliasis ).• Excretion is via kidneys.• Severe effects needs interruption of therapy.• adverse effects:• Diarrhea ,nausea , vomiting ,anorexia, skin reaction,

dizziness headche.• Caution: in children

Drugs for the treatment of Cestodes• Niclosamide:• Second line drug for most tapeworm infections.• Drug should be given in morning on an empty stomach.• Adult worms are rapidly killed due to inhibition of

oxidative phosphorylation or stimulation of ATPase activity.

• Clinical uses;( beef ,pork,fish,dog tapeworm), Cycticercosis .

• Adverse effects:mild nausea , vomiting , diarrhea,and abdominal discomfort.

• Contra : alcohol

Albendazole • A broad spectrum oral antihelimintics and drug of choice for

hydatid disease and cysticercosis. • It is a benzimidazole carbamate.• Half life---8-12 hrs• Excreted in urine• Should b given empty stomach when used against intraluminal

parasite but with fatty meal when used against tissue parasite.• Clinical uses: ascariasis , trichuriasis, hookworm, pinworm

infections, hydatid disease, neurocysticercosis.• Adverse effects: insomnia, diarrhea, lassitude, nausea, long

term (pancytopenia ,alopecia, liver enzymes increased).• Contra : hypersenstivity to albendazole, pregnancy, children

under 2 yrs.

•Thank you