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By Medifit Education



 Antiprotozoals 1


Antiprotozoal drug, any agent that kills or inhibits the growth of organisms known as protozoans.



Antiprotozoal drugs are used to treat a variety of diseases caused by protozoa. Protozoa are animal-like, one-celled animals, such as amoebas. Some are parasites that cause infections in the body. Protozoans cause a variety of diseases, including malaria and Chagas’ disease. While protozoans typically are microscopic, they are similar to plants and animals in that they are eukaryotes and thus have a clearly defined cell nucleus. This distinguishes them from prokaryotes, such as bacteria. As a result, many of the antibiotics that are effective in inhibiting bacteria are not active against protozoans.



Something that destroys protozoa or inhibits their growth and ability to reproduce.

A few of the protozoa of medical importance include Plasmodium (the cause of malaria); Entamoeba histolytica (the cause of amebiasis, amebic dysentery) and Trichomonas vaginalis (a cause of vaginal infection); and Pneumocystis carinii (a common cause of pneumonia in immunodeficient persons).

Some antiprotozoal drugs include the antimalarials Aralen (chloroquine), Daraprim (pyrimethamine), Lariam (mefloquine) and Plaquenil (hydroxychloroquine); Flagyl (metronidazole) which is active against Entamoeba histolytica and Trichomonas vaginalis; and Mepron (atovaquone) for Pneumocystis carinii.


Side effects

The most common side effects are diarrhea, nausea, vomiting, and stomach pain. These problems usually go away as the body adjusts to the drug and do not require medical treatment.

Other rare side effects may occur. Anyone who has unusual symptoms after taking an antiprotozoal drug should get in touch with his or her physician.



Antiprotozoal drugs may interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes antiprotozoal drugs should let the physician know all other medicines he or she is taking. Among the drugs that may interact with antiprotozoal drugs are:

  • Alcohol
  • Anticancer drugs
  • Medicine for overactive thyroid
  • Antiviral drugs such as zidovudine (Retrovir)
  • Antibiotics
  • Medicine used to relieve pain or inflammation
  • Amphetamine
  • Diet pills (appetite suppressants)
  • Monoamine oxidase inhibitors (MAO inhibitors) such as phenelzine (Nardil) and tranylcypromine (Parnate), used to treat conditions including depression and Parkinson’s disease.
  • Tricyclic antidepressants such as amitriptyline (Elavil) and imipramine (Tofranil)
  • Decongestants such as phenylephrine (Neo-Synephrine) and pseudoephedrine (Sudafed)
  • Other antiprotozoal drugs.

The list above does not include every medicine that may interact with an antifungal drug. Be sure to check with a physician or pharmacist before combining antifungal drugs with any other prescription or nonprescription (over-the-counter) medicine.

Antiprotozoals 2

By Medifit Education