Antiprotozoals for trichomoniasis


Generic Name Brand Name
metronidazole Flagyl
tinidazole Tindamax

Both metronidazole and tinidazole are approved by the U.S. Food and Drug Administration (FDA) for the treatment of trichomoniasis.

How It Works

Antiprotozoals kill the tiny parasite (a one-celled protozoan organism) that causes trichomoniasis (trich).

Why It Is Used

These medicines are used to cure trichomoniasis by destroying the parasite that causes the condition.

Oral metronidazole can be taken either as a single dose (2 g) or as multiple doses (500 mg) 2 times a day for 7 days. A single oral dose of 2 g metronidazole can be taken by a pregnant woman if needed.1 Women who are breast-feeding will be instructed by their health professional on the use of metronidazole.

The treatment regimen with tinidazole is a one-time dose of 2 g. Tindamax is available in strengths of 250 mg and 500 mg tablets, so you may take one or two tablets up to 4 times in 1 day to total the recommended dose of 2 g. Pregnant women should not take tinidazole because it is not yet clear whether this medicine is safe to use during pregnancy.

How Well It Works

The cure rate in treating trichomoniasis using metronidazole is 90% to 95%.1

The cure rate using tinidazole is 86% to 100%.1

Sex partners should be treated at the same time. Sexual intercourse should be avoided until symptoms are gone. Men may not have any symptoms but still need treatment.

People who are infected with HIV receive the same treatment for trich as those who are HIV-negative.


  • No follow-up is needed if symptoms go away.
  • If symptoms do not go away, you may need to take the medicine again.
  • If treatment fails after this and you have not been reinfected, further testing may be done to determine the cause of your symptoms. It is possible to have a strain of trich that is resistant to metronidazole. High-dose tinidazole is used for metronidazole-resistant trich organisms and is as effective as metronidazole in curing trich.2

Metronidazole vaginal suppositories or creams are not recommended because oral metronidazole is much more effective. Vaginal medicines cure trich in less than 50% of cases.1 Metronidazole vaginal gel, which is used to treat bacterial vaginosis, is not recommended by the CDC for treatment of trich.1

Side Effects

Common and expected side effects include:

  • Metallic taste in the mouth.
  • Dark urine color.
  • Nausea and vomiting with the higher dose of metronidazole or with use of alcohol, or products that contain alcohol, during treatment.

These side effects will go away once the medicine is stopped.

Although a rare side effect, metronidazole may cause pancreatitis, an inflammation of the pancreas, in some people. Also, metronidazole may not cure trich in some people. When treatment resistance or severe side effects occur, another type of treatment will be needed.3

Caution: Do not use alcohol or products that contain alcohol (such as nonprescription nighttime cold medicines) while taking metronidazole or tinidazole. You should not use alcohol for at least 3 days after your last dose of these medicines. Alcohol interacts with the medicines, and the combination can cause nausea, abdominal cramps, headaches, reddening of the face, and vomiting.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

The oral form of these medicines is the most effective treatment for trichomoniasis.

Oral metronidazole can be taken by pregnant women at any time during pregnancy.

While taking these medicines and for at least 3 days after your last dose, do not use alcohol or products that contain alcohol.

Trich during pregnancy raises the risk of premature rupture of membranes (PROM) and premature delivery. Treating the infection does not appear to reduce this risk.2 If you are pregnant and have trich, talk to your doctor about the pros and cons of treatment.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.



  1. U.S. Department of Health and Human Services (2006). Sexually Transmitted Diseases Treatment Guidelines, 2006 (CDC Publication Vol. 55, No. RR-11), pp. 52–54. Atlanta: U.S. Department of Health and Human Services. Also available online:
  2. American College of Obstetricians and Gynecologists (2006). Vaginitis. ACOG Practice Bulletin No. 72. Obstetrics and Gynecology, 107(5): 1195–1206.
  3. Feola DJ, et al. (2002). Metronidazole-induced pancreatitis in a patient with recurrent vaginal trichomoniasis. Pharmacotherapy, 22(11): 1508–1510.

Last Updated: July 22, 2008

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