4. Antihelminthic agents. Classification. Mechanism of action. Indications for use. Side effects. Contraindications Comparative evaluation of drugs.

Anthelminthic agents disrupt the function of the neuromuscular system of helminths, exhibiting anticholinesterase (emetine), cholinomimetic (ditrazine, combantrine) or anticholinergic (piperazine) action. Many drugs (levamisole and others) disrupt various types of metabolism in helminths

Mechanisms of action	Drugs
Cell poisons	Ethylene tetrachloride
Drugs that disrupt the function of the neuromuscular system in roundworms	Piperazine, ditrazine
Drugs that paralyze the neuromuscular system in flatworms and destroy integumentary tissues	Fenasal, Bithionol
Means acting on the energy processes of helminths	Aminoacriquine, Levamisole, Pirvinia pamoat, Oxygen

The effectiveness of antihelminthic agents for various helminthiasis is not the same and is primarily determined by the biological species of parasitic worms and their localization in the body. On the basis of ideas about the direction of action of drugs on various classes of helminths, a classification of antihelminthic agents is constructed. In accordance with this, funds are allocated that are used mainly for the treatment of nematodes, cestedoses and trematodes.

Anthelminthic agents used mainly for nematodes

A drug	Helminthiasis
Citric Seed (Santonin)	Ascariasis
Levamisole (decaris)	Ascariasis
Piperazine adipate (vermitox)	Ascariasis, enterobiasis
Naphtamon (befenium)	Ankyostomosis, trichocephalosis
Diphezil	Trichocephalosis
Pirantel (Combatrin)	Enterobiasis, ascariasis, non-cardiosis
Thiabenzadol (mintezol)	Strongyloidiasis, noncatorosis, trichinosis
Ditrazine (notezin)	Filariasis

Anthelminthic drugs used mainly for cestodosis

A drug	Helminthiasis
Male fern extract	Teniosis, teniarinchiasis, hymenolepiasis, diphyllobothriasis
Fenasal (niclosamide)	Teriarynchiasis, diphyllobothriasis, hymenolepiasis

Broad-spectrum anti-herbal remedies

A drug	Helminthiasis
Ambilgar (niridazole)	Nematodes, trematodes
Praxivantel (Pickwiton)	Cestodoses, trematodes
Mebendazole (vermox, mebenvent)	Nematodes, trematodes, cestodoses
Albendazole (Zentel)	Nematodoses, cestodoses
Bithionol (actamer)	Nematodoses, cestodoses

One of the most effective remedies for ascariasis is levamisole (decaris). A single injection of the drug leads to deworming in 90 - 100% of patients, regardless of the degree of their infection. Unlike santonin, the drug acts on ascaris of all age groups. Levamisole is less effective in ankylostomiasis and strongyloidiasis.

The mechanism of the anthelmintic action of levamisole is based on the specific inhibition of the enzyme succinate dehydrogenase, as a result of which the fumarate reduction reaction, which is most important for nematodes, is blocked. It should be borne in mind that levamisole does not affect succinate dehydrogenase in mammals and only inhibits the helminth enzyme.

The main indication for the use of the drug is ascariasis. Treatment with levamisole (unlike treatment with many anthelmintic drugs) does not require preliminary preparation of the patient - a special diet, the use of laxatives, etc. It is used once before bedtime (for adults at a dose of 150 mg). The drug is well tolerated.

In the treatment of cestodoses, the most common remedy is male fern extract, which is highly toxic and requires careful special preparation of the patient. The main active principles of the male fern extract - philicic acid, aspidin and desaspidin - cause paralysis of the neuromuscular apparatus of flatworms.

Treatment is carried out according to a specific scheme, including diet and laxatives. The dose of the extract for adults is up to 8 g. Often there are numerous side effects in the form of nausea, vomiting, abdominal pain, palpitations. Convulsions, collapse, heart failure are possible. These side and toxic effects, as well as certain contraindications, limit the use of male fern preparations.

In modern medical practice, for the treatment of cestodosis, fenasal is mainly used, which is highly effective in theriarynchiasis, diphyllobothriasis and hymenolepiasis. Fenasal paralyzes tapeworms. In addition, it causes the destruction of the integumentary tissues of helminths and reduces their resistance to the action of proteolytic enzymes of the gastrointestinal tract, contributing to the digestion of cestodes (in this regard, phenasal is not recommended for use in teniasis due to the risk of developing cystcercosis).

Treatment with fenasal does not require special preparation of patients. It is usually taken at night after a light dinner at a dose of 3 g (for adults); with hymenolepiasis, a course treatment is carried out.

The drug is well tolerated. The high efficiency of phenasal in cestodosis, the absence of contraindications and pronounced side effects ensures its widespread use in medical practice, not only in adults, but also in children.