Examples

How It Works

These medicines kill Giardia lamblia in the digestive tract.

Metronidazole comes in tablet and liquid forms. It usually is taken in tablet form for 3 to 7 days for treatment of giardiasis.

Tinidazole comes in tablet form. It usually is taken for 1 day either in one dose or in several doses throughout the day.

Why It Is Used

These medicines are used to treat certain bacterial and parasite infections. They also are an effective treatment for giardiasis infection.

These medicines may be used if stool analysis or other testing shows giardiasis infection is present.

If your doctor thinks that your symptoms are caused by giardia, he or she may prescribe one of these medicines even before your test results are back.

If you are pregnant, talk with your doctor or pharmacist before taking these medicines.

How Well It Works

Metronidazole cures giardiasis in adults 80% to 95% of the time.¹

Tinidazole is very effective for the treatment of giardiasis. A single dose often cures the infection with very few side effects.²

Side Effects

The most common side effects of these medicines include:

• A metallic taste in the mouth.
• Nausea, vomiting.
• Dizziness.
• Headache.

A rare side effect is a low number of white blood cells (neutropenia, leukopenia). The white blood cell count returns to normal when you stop taking the drug.

Do not drink alcohol while you are taking metronidazole or tinidazole. Using alcohol while you are taking these medicines can cause headaches, nausea, reddening of the face, belly cramps, and vomiting. You should also avoid alcohol for at least 3 days after you finish your last dose of these medicines.

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

What To Think About

Metronidazole may be used with caution in pregnant women.

Do not use alcohol while you are taking either of these medicines or for 3 days after you finish your last dose.

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

References

Citations

1. Hill DR (2005). Giardia lamblia. In GL Mandell et al., eds., Principles and Practice of Infectious Disease, 6th ed., vol. 2, pp. 3198–3205. Philadelphia: Elsevier.
2. Rosenthal PJ, Goldsmith RS (2008). Giardiasis section of Protozoal and helminthic infections. In SJ McPhee et al., eds., Current Medical Diagnosis and Treatment, 47th ed., pp. 1309–1311. New York: McGraw-Hill Medical.