Antiprotozoals for trichomoniasis

Examples

Generic Name	Brand Name
metronidazole	Flagyl

Metronidazole is approved by Health Canada 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

This medicine is 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.

How Well It Works

The cure rate in treating trichomoniasis using metronidazole is 90% to 95%.²

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.

Follow-up

• No follow-up is needed if symptoms go away.
• If symptoms do not go away, you may need to take the medicine again.
• Vaginal metronidazole may be added to the oral treatment for increased effectiveness.
• 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. If this is the case, you may need to take a large dose of metronidazole. This will usually cure the infection.

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.² Vaginal medicines are not effective in treating trich in areas other than the vagina and cervix. Metronidazole vaginal gel, which is used to treat bacterial vaginosis, is not recommended by the Public Health Agency of Canada (PHAC) for treatment of trich.¹

Side Effects

Common and expected side effects include:

• Metallic taste in the mouth.
• Dark urine colour.
• 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 non-prescription nighttime cold medicines) while taking metronidazole. You should not use alcohol for at least 3 days after your last dose of this medicine. Alcohol interacts with the medicine, 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 this medicine 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.

Trichomoniasis during pregnancy raises the risk of premature rupture of membranes (PROM) and premature delivery. Treating the infection does not appear to reduce this risk.⁴ If you are pregnant and have trich, talk to your doctor about the pros and cons of treatment.

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Author:	Amy Fackler, MA Debby Golonka, MPH Carrie Henley	Last Updated: November 13, 2006
Medical Review:	Larry J. Anderson, MD - Infectious Disease Renée M. Crichlow, MD - Family Medicine Adam Husney, MD - Family Medicine Jeanne Marrazzo, MD, MPH - Infectious Disease Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology
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