Antiparasitics are class of medications which are employed for treatment of parasitic diseases. Parasitic infections are caused by parasites [helminths, amoeba, parasitic fungi, protozoa etc.]
They target parasitic agents of the infections by destroying them or inhibiting their growth & are usually effective against limited number of parasites within a particular class (Narrow spectrum). Broad-Spectrum antiparasitics are drugs with efficacy in treating a wide range of parasitic infections caused by parasites from different classes.
They may be administered orally, intravenously or topically.
Some antiparasitics are metronidazole, tinidazole, pyrimethamine, pentamidine, nitazoxanide etc.
Effectiveness– They must have broad spectrum of action & active against all developmental stages of the parasite as well as against both tissue and luminal forms.
Safe– They should be safe for use with low or nil toxicity, should not discolor body fluids or & no tissue residues and/or a short withdrawal time. There should not be interaction with other drugs or environmental toxins.
Convenient to use- They should be convenient for use with effective one dose treatment to minimize the cost and must have dose forms that are easy to administer. No-purgation is ideal as it decreases the number of drugs, number of handlings, and the resultant mess.
Low cost- The drug must be cost effective particularly in mass therapy situations, it must be inexpensive to administer.
Antiparasitics, drugs which kill or inhibit the growth of parasitic organisms, may be subdivided into the following major therapeutic categories:
Antiprotozoal: Medications for protozoal diseases are termed as antiprotozoals. They are used against various infections which include amoebiasis, giardiasis, cryptosporidiosis, microsporidiosis, malaria, babesiosis, trypanosomiasis, Chagas disease, leishmaniasis and toxoplasmosis. Currently, many of the treatments for these infections are limited by their toxicity.
The mechanisms of antiprotozoal drugs differ significantly drug to drug.
- Eflornithine, a drug used for treating trypanosomiasis, inhibits ornithine decarboxylase.
- Aminoglycoside antibiotic/antiprotozoal used to treat leishmaniasis are thought to inhibit protein synthesis.
Antihelmintics: These are the substances used to inhibit or kill helminthic/worm parasites. These are also called wormers. Helminths are parasitic worms that feed on a living host to gain nourishment and protection, while causing poor nutrient absorption, weakness and disease in the host. It can be antinematodal, anticestodal as well as antitrematodal.
There are two main types of antihelmintics: those that act more rapidly on membrane ion-channels and those that act biochemically and more slowly.
- Antinematodal: Substances used in the treatment or control of nematode infestations or agents designed to reduce nematode infection i.e. roundworm infections. Some examples are piperazine, imidazothiazoles, benzimidazole a tetrahydropyrimidines (tetramizole, levamisole etc.) and pro-benzimidazoles (thiabendazole, mebendazole etc.).
- Anticestodal: Drug used to combat tapeworm infection or inhibit/ treat tapeworm infestations. It include natural organic compound arecoline and the synthetic compounds bunamidine, dichlorophen, praziquantel, uredofos, niclosamide and resorantel etc.
- Antitrematodal: Medications against trematode infections i.e. fluke infestations. Because of the lower susceptibility to injury of immature flukes measure of efficiency of antitrematodal drugs is measured by their efficiency against immature flukes. It Includes albendazole, bithionol sulfoxide, bromsalans, carbon tetrachloride,clioxanide, niclofolan, triclabendazole etc.
Antimalarial: They are drugs mainly used to control symptoms of malaria, e.g. chloroquine & primaquine.
- Chloroquine oral tablet plays a role in the invasion of red blood cells within the parasite period, which will effectively control the onset of symptom.
- Primaquine is used for the prevention of malaria recurrence and spread of drugs. It is mainly used for eradicating vivax malaria and controlling malaria transmission.
Antifilarial: These are agents to control filariasis , parasitic disease caused by an infection with roundworms of the Filarioidea type. Ivermectin, diethylcarbamazine etc are commonly used antifilarials.
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