Encyclopedia / M / Metronidazole



Metronidazole is an antiprotozoal drug with antibacterial effects. It is often given orally.


Metronidazole belongs to the family of medicines called anti-infectives. It is often used to treat infections and bacterial and trichomonal vaginitis, as well as a wide variety of systemic infections (including dysentery) and infections of the respiratory tract, bones, joints and stomach. A commonly used brand name of metronidazole is Flagyl. Flagyl is available in oral and parenteral (IV) form and is usually given orally.

Side Effects

Drinking alcoholic beverages while taking this medication may cause stomach pain, nausea, vomiting, headache and flushing or redness of the face. You should not drink alcoholic beverages or take other alcohol-containing preparations while you are taking this medicine and for at least a day after stopping it.

Other side effects may include numbness, tingling, pain or weakness in hands or feet.

Less common side effects include vaginal irritation, discharge or dryness (not present before use of the medicine); clumsiness or unsteadiness; mood or mental changes; skin rash; hives; redness or itching.

If given intravenously, side effects may include pain, tenderness, redness or swelling over the vein in which the medicine is given.

Metronidazole should not be used in the first trimester of pregnancy. If taken with warfarin (Coumadin), it may increase the likelihood of bleeding. Therefore, inform your physician of any and all medications you are taking.


What are the chances that I could be allergic to this medication and develop severe and life-threatening reactions?

What signs and symptoms should the doctor be notified of immediately?

If taken orally, is the medication best taken with food?

Are there any special instructions in taking this medication?