ANTHELMINTHIC DRUGS-PART-I

HELMINTHIASIS-TREATMENTS

Helminthiasis is a collective name for infections of the GI tract with a variety of intestinal worms. Helminth is a Greek word for worms.

Classifications

1.Nematodes (roundworms)

2.Trematodes (flukes)

3.Cestodes (tapeworms)

The last two are unlike the roundworms they are flat in structure, so the types of flatworms.  

A.Drugs for Nematodes (Roundworms)

These are the worm infections more commonly occur.

1.Mebendazole  

Available in the pharmacy as OTC medicine by the brand name of Vermox

Mebendazole is the drug of choice for pinworm (Enterobius vermicularis); and whipworm (Trichuris trichiura).

It is also effective against hookworm (Necator americanus); and roundworm (Ascaris lumbricoides)

Mebendazole acts by interfering with the parasite's microtubules and decrease glucose uptake.

When given orally only a minute quantity is absorbed into the system and most of the drugs remain in the gut for action. 

During Pregnancy this medicine is not safe as it is proved as teratogenic in animal experiments.

Generally most anthelmintic drugs are not safe during pregnancy.

Side effects

Adverse effects are usually mild and the most frequent effects are nausea; vomiting;

Rarely intrahepatic cholestasis is reported as a condition in which the bile is blocked and collected abnormally inside the liver and not secreted into the duodenum.

2.Thiabendazole

Actions are similar to mebendazole.

It can be given orally.

It is used against the infection caused by threadworm (Strongyloides stercoralis); Cutaneous larva migrans (CLM)  caused by Ancylostoma in which the hookworm infections spread outside the body to the skin.

Visceral Larva Migrans caused by Toxocara (the roundworm infections in dogs, cat, and fox).Thiabendazole is the drug to be used for this.

Side effects

1.CNS effects like tingling and numbness

2.Diarrhea and nausea

3.Reactions caused by dying parasites such as fever, chills, and lymphadenopathy(swollen abnormal lymph nodes)

4.Sevens-Jhonson syndrome (Rare)

3.Albendazole

It is a newer broad-spectrum anthelmintic among the benzimidazoles group like mebendazole and thiabendazole.

Action is similar to the other two benzimidazoles by blocking the glucose uptake.

Side effects

Milder like nausea vomiting and dizziness

4.Pyrantel pamoate

Drug of choice for treating ascariasis

It also can be used for pinworms and hookworms.

Unlike benzimidazoles its mechanism of action is different. It acts as a depolarizing neuromuscular blocking agent that cause continuous stimulation of parasympathetic nicotinic receptors of the Nm type of the parasites and causes them to paralysis 

Side effects

Milder like nausea; vomiting; headache and rash

5.Diethylcarbamazine(Hetrazan)

This is the drug of choice for the treatment of filariasis caused by Wuchereria bancrofti

Mechanism of action is thought to decrease the muscular activity of the parasites.

Also can be used to treat the infections caused by onchocerca vulvulus to cause onchocerciasis characterized by severe itching skin bumps and blindness.

Side effects

Mild like nausea; headache; and vomiting.

Treatment for onchocerciasis may lead to a reaction known as Mazzotti reaction as a result of dying parasites and is characterized by pruritus; lymphadenopathy; hypotension followed by tachycardia.

6.Ivermectin

This is the drug of choice for river blindness caused by onchocerca vulvulus. and also for threadworm infections caused by Strongyloides stercoralis

The drug intensifies GABA mediated nerve transmission in nematodes and causes them to sleep.

The drug is, fortunately, acting selectively at the GABA receptors of the parasites only and not at the human receptors.

Also ivermectin does not cross the blood-brain barrier and hence not causes CNS side effects.

Side effects

Fever, headache, dizziness, and pruritus.