Anthelmintic drugs are used to eradicate or reduce the numbers of helminthic parasites in the
intestinal tract or tissues of the body. Most anthelmintics are active against specific parasites;
thus, parasites must be identified before treatment is started.
Individual Drugs
Albendazole
Albendazole, a broad-spectrum oral anthelmintic, is used for pinworm infection, ascariasis,
trichuriasis, strongyloidiasis, and infections with both hookworm species. Albendazole is also
the drug of choice in hydatid disease and cysticercosis.
Anthelmintic Actions: Albendazole blocks glucose uptake by larval and adult stages of
susceptible parasites, depleting their glycogen stores and decreasing formation of ATP. As a
result the parasite is immobilized and dies. The drug has larvicidal effects in necatoriasis and
ovicidal effects in ascariasis, ancylostomiasis, and trichuriasis. The drug is teratogenic and
embryotoxic in some animal species and contraindicated in the first trimester.
Clinical Uses
- Ascariasis, Trichuriasis, and Hookworm and Pinworm Infections: For pinworm infections,
ancylostomiasis, and light ascariasis, necatoriasis, or trichuriasis, a single dose of 400 mg is
given orally for adults and in children over two years of age. In pinworm infection, the dose
should be repeated in 2 weeks. - Strongyloidiasis: 400 mg twice daily for three days (with meals).
- Hydatid Disease: 800 mg/kg/d in divided doses for three months
- Neurocysticercosis: 15 mg/kg /d for 8 days
- Other Infections: At a dosage of 200-400 mg twice daily, albendazole is the drug of choice in
treatment of cutaneous larval migrans (give daily for 3-5 days) and in intestinal capillariasis
(10-day course).
Adverse Reactions: Mild and transient epigastric distress, diarrhea, headache, nausea,
dizziness. In 3-month treatment courses causes jaundice, nausea, vomiting, abdominal pain,
alopecia, rash or pruritus occurs.
Diethylcarbamazine Citrate
Diethylcarbamazine is a drug of choice in the treatment of filariasis, loiasis, and tropical
eosinophilia.
Anthelmintic Actions: Diethycarbamazine immobilizes microfilariae and alters their surface
structure, making them more susceptible to destruction by host defense mechanisms. The
mode of action of diethylcarbamazine against adult worms is unknown.
Clinical Uses: - Wuchereria bancrofti, Loa loa: Diethycarbamazine is the drug of choice for treatment of
infections with these parasites, given its high order of therapeutic efficacy and lack of
serious toxicity. Microfilariae of all species are rapidly killed; adult parasites are killed more
slowly, often requiring several courses of treatment. - Onchocerca volvulus: Diethylcarbamazine temporarily kills microfilariae but are poorly
effective against adult worms. If diethylcarbamazine is used in onchocerciasis treatment,
suramin (a toxic drug) must be added to the regimen to kill the adult worms.
Adverse Reactions
Reactions to the drug itself are mild and transient includes: headache, malaise, anorexia, and
weakness are frequent. Reactions Induced by dying Parasites: As a result of the release of
foreign proteins from dying microfilariae or adult worms in sensitized patients. Reactions in
onchocerciasis affect the skin and eyes in most patients. The reactions may be severe, if
infection is heavy. Vision can be permanently damaged as a result of dying microfilariae in the
optic disks and retina. Reactions in W bancrofti, and L loa infections are usually mild in W
bancrofti, and occasionally severe in L loa infections. Reactions include fever, malaise, papular
rash, headache, gastrointestinal symptoms, cough, chest pains, and muscle or joint pains.
Ivermectin
Ivermectin is the drug of choice in individual and mass treatment of onchocerciasis and for
strongyloidiasis. The drug is rapidly absorbed. The drug has a wide tissue distribution. It
apparently enters the eye slowly and to a limited extent. Excretion of the drug and its
metabolites is almost exclusively in the feces.
Anthelmintic Actions: Ivermectin paralyze nematodes and arthropods by intensifying GABAmediated transmission of signals in peripheral nerves. In onchocerciasis, ivermectin is
microfilaricidal and affects embryogenesis. The mode of action of ivermectin on microfilariae is
uncertain.
Clinical Uses: Onchocerciasis, Bancroftian Filariasis, Strongyloidiasis, scabies and cutaneous
larva migrans
Adverse Reactions: The adverse effects of ivermectin are the Mazotti reaction, which starts on
the first day after a single oral dose and peaks on the second day. The reaction is due to killing
of microfilariae and its intensity correlates with skin microfilaria loads. The Mazotti reaction
includes fever, headache, dizziness, somnolence, weakness, rash, increased pruritus, diarrhea,
joint and muscle pains, hypotension, tachycardia, lymphadenitis, lymphangitis, and peripheral
edema. The Mazotti reaction diminishes with repeated dosing. Steroids may be necessary for
several days.
Levamisole
Levamisole hydrochloride is highly effective in eradicating Ascaris and moderately effective
against both species of hookworm.
Mebendazole
Mebendazole has a broad spectrum of anthelmintic activity and a low incidence of adverse
effects. Poorly absorbed after oral adminstration. It rapidly metabolized and excreted mostly in
the urine, either unchanged or as decarboxylated derivatives.
Mebendazole inhibits microtubule synthesis in nematodes, thus irreversibly impairing glucose
uptake. As a result, intestinal parasites are immobilized or die slowly.
Clinical Uses: The drug can be taken before or after meals; the tablets should be chewed
before swallowing. - Pinworm Infection: Give 100 mg once and repeat the dose at 2 and 4 weeks
- Ascaris lumbricoides, Trichuris trichiura, and Hookworm
- Hydatid Disease: Mebendazole is the alternative.
- Taeniasis: In Taenia solium infection, mebendazole has a theoretic advantage over
niclosamide in that proglottids are expelled intact. - Strongyloidiasis.
Adverse Reactions: Mild nausea, vomiting, diarrhea, and abdominal pain have been reported
infrequently, more often in children heavily parasitized by Ascaris.
Metrifonate
Metrifonate is a safe, alternative drug for the treatment of Schistosoma haematobium infections.
Metrifonate, an organophosphate compound, is rapidly absorbed after oral administration.
Clearance appears to be through nonenzymatic transformation to its active metabolite
(dichlorvos). Metrifonate and the active metabolite are well distributed to the tissues and are
completely eliminated in 24-48 hours.
Adverse Reactions: mild and transient cholinergic symptoms, including nausea and vomiting,
diarrhea, abdominal pain, bronchospasm, headache, sweating, fatigue, weakness, dizziness,
and vertigo.
Niclosamide
Niclosamide is a drug of choice for the treatment of most tapeworm infections. It appears to be
minimally absorbed from the gastrointestinal tract: neither the drug nor its metabolites have
been recovered from the blood or urine.
Clinical Uses: Niclosamide should be given in the morning on an empty stomach. The tablets
must be chewed thoroughly and are then swallowed with water. - T saginata, T solium, and Diphyllobothrium latum: A single 2 g dose of niclosamide results in
cure rates of over 85% for D latum and about 95% for T saginata. - Hymenolepis nana and H: Niclosamide is effective against the adult parasites in the lumen of
the intestine. The minimum course of treatment must be 7 days - Intestinal Fluke Infections: Niclosamide can be used as an alternative drug for the treatment
of intestinal flukes.
Adverse Reactions: Adverse effects, mild, and transitory. It causes nausea, vomiting, diarrhea,
and abdominal discomfort.
Oxamniquine
Oxamniquine is used for the treatment of S mansoni infections. It is active against both mature
and immature stages of S mansoni. It has also been used extensively for mass treatment.
Oxamniquine is readily absorbed orally.
Clinical Uses: Oxamniquine is safe and effective in all stages of S mansoni disease, including
advanced hepatosplenomegaly. It is better tolerated if given with food, although food delays
absorption. In mixed infections with S mansoni and S haematobium, oxamniquine has been
successfully used in combination with metrifonate.
Adverse Reactions: Central nervous system symptoms are most common; nausea and
vomiting, diarrhea, colic, pruritus, and urticaria also occur.
Piperazine
The piperazine salts are alternative drugs in the treatment of ascariasis. Piperazine is readily
absorbed from the gastrointestinal tract, and maximum plasma levels are reached in 2-4 hours.
Most of the drug is excreted unchanged in the urine in 2-6 hours.
Anthelmintic Actions: Piperazine causes paralysis of Ascaris by blocking acetylcholine at the
myoneural junction. The paralyzed roundworms are unable to maintain their position in the host
and are expelled live by normal peristalsis.
Clinical Uses: Ascariasis
Adverse Reactions: Piperazine cause nausea, vomiting, diarrhea, abdominal pain, dizziness,
and headache.
Praziquantel
Praziquantel is effective in the treatment of schistosome infections of all species and most other
trematode and cestode infections, including cysticercosis. The drug’s safety and effectiveness
as a single oral dose have also made it useful in mass treatment of several of the infections. It
is rapidly absorbed after oral administration. Most of the drug is rapidly metabolized to inactive
products after a first pass in the liver. Excretion is mainly via the kidneys and bile.
Anthelmintic Actions: Praziquantel drug increases cell membrane permeability to calcium,
resulting in marked contraction, followed by paralysis of worm musculature. Vacuolization and
disintegration of the tegumen occur, and parasite death follows.
Clinical Uses: - Schistosomiasis: Praziquantel is the drug of choice for all forms of schistosomiasis.
- Taeniasis and Diphyllobothriasis: A single dose of praziquantel, 10 mg/kg.
- Neurocysticercosis: The praziquantel dosage is 50 mg/kg/d in three divided doses for 14
days.
193 - H nana: Praziquantel is the drug of choice for H nana infections and the first drug to be
highly effective. A single dose of 25 mg/kg is used.
Adverse Reactions: Most frequent are headache, dizziness, drowsiness, and lassitude; others
include nausea, vomiting, abdominal pain, loose stools, pruritus, urticaria, arthralgia, myalgia,
and low-grade fever. Praziquantel appears to be better tolerated in children than in adults.
Adverse effects may be more frequent in heavily infected patients, especially in S mansoni
infections.
Pyrantel Pamoate
Pyrantel pamoate is a broad-spectrum anthelmintic highly effective for the treatment of pinworm
and Ascaris. Pyrantel pamoate because it is poorly absorbed from the gastrointestinal tract, it is
active mainly against luminal organisms.
Anthelmintic Actions: Pyrantel is effective against mature and immature forms of susceptible
helminths within the intestinal tract but not against migratory stages in the tissues or against
ova. The drug is a depolarizing neuromuscular blocking agent that causes release of
acetylcholine and inhibition of cholinesterase; this results in stimulation of ganglionic receptors
and worm paralysis, which is followed by expulsion from the host’s intestinal tract.
Clinical Uses: The standard dose is 11 mg (base)/kg (maximum, 1 g), given with or without
food. Pyrantel is given as a single dose and repeated in 2 and 4 weeks is effective in
Enterobius vermicularis, A lumbricoides, and hookworm infections.
Suramin
Suramin is an alternative drug for the eradication of adult parasites of Onchocerca volvulus and
a drug of choice in the treatment of the hemolymphatic stage of African trypanosomiasis due to
Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Suramin is a
nonspecific inhibitor of many enzymes. Toxic reactions are frequent and sometimes severe,
including nausea, vomiting, urticaria, fever, nephrotoxicity, peripheral neuritis, anemia, jaundice,
and exfoliative dermatitis. The drug should be given only under expert guidance.
Thiabendazole
Thiabendazole is the drug of choice for the treatment of strongyloidiasis and an alternative drug
for cutaneous larva migrans. It may also be tried in trichinosis and visceral larva migrans, given
in the absence of other effective drugs. It is no longer recommended for the treatment of
pinworm, ascarid, trichurid, or hookworm infection unless the safer drugs of choice are not
available. Thiabendazole is rapidly absorbed after ingestion. The drug is almost completely
metabolized in the liver. Ninety percent of the drug is excreted in the urine.
Anthelmintic Actions: Thiabendazole has anti-inflammatory properties, which may be an
important factor in its ability to relieve symptoms in some parasitic diseases. It also has
immunomodulating effects on T cell function appears to be an immunorestorative agent.
Thiabendazole also has antipyretic and mild antifungal and scabicidal actions. Thiabendazole’s
vermicidal action may be a result of interference with microtubule aggregation acting through
inhibition of the enzyme fumarate reductase. The drug has ovicidal effects for some parasites.
Clinical Uses: The standard dose is 25 mg/kg (maximum, 1.5 g). The drug should be given after
meals. Effective in Strongyloides stercoralis (The standard dose is given twice daily for 2 days).
In patients with hyperinfection syndrome, the standard dose is continued twice daily for 5-7
days. Thiabendazole is highly effective in the treatment of cutaneous larva migrans. Cutaneous
Larva Migrans (Creeping Eruption) The standard dose is given twice daily for 2 days.
Adverse Reactions: Adverse effects are generally mild and transient but can be severe; the
most common are dizziness, anorexia, nausea, and vomiting.
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