Drug Information

Metronidazole is an antibiotic used to treat a variety of bacterial and parasitic infections, such as amebiasis, trichomoniasis, and giardiasis. It is also used as a component of multidrug antibiotic combinations to heal stomach and duodenal ulcers caused by Helicobacter pylori infections. Metronidazole is available alone and in a combination product.

From Vaginal Intro (733)

Metronidazole (vaginal) is an intravaginal antibiotic used to treat vaginal infections caused primarily by bacteria. Metronidazole is also available as oral and topical medications.

Common brand names:

Flagyl, MetroGel Vaginal, Noritate, MetroCream, MetroGel, Vandazole

Summary of Interactions with Vitamins, Herbs, & Foods

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • none

Reduce Side Effects

  • Probiotics

    The yeast Saccharomyces boulardii may help restore microbial balance in the intestines and prevent pseudomembranous colitis (PMC), an intestinal disorder caused by infection with Clostridium difficile. Even when Clostridium difficile is successfully treated with antibiotics, symptoms recur in about 20% of cases. Saccharomyces boulardii has been shown in controlled trials to reduce recurrences when given as an adjunct to antibiotic therapy.1 , 2 , 3

Support Medicine

  • none

Reduces Effectiveness

  • none

Potential Negative Interaction

  • none

Explanation Required 

  • Milk Thistle

    Milk thistle has been reported to protect the liver from harm caused by some prescription drugs.4 While milk thistle has not yet been studied directly for protecting people against the known potentially liver-damaging actions of metronidazole, it is often used for this purpose.

The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.


1. Surawicz CM, McFarland LV. Pseudomembranous colitis: causes and cures. Digestion 1999;60:91-100 [review].

2. Eddy JT, Stamatakis MK, Makela EH. Saccharomyces boulardii for the treatment of Clostridium difficile-associated colitis. Ann Pharmacother 1997;31:919-21.

3. McFarland LV, Surawicz CM, Greenberg RN, et al. A randomized placebo-controlled trial of Saccharomyces boulardii in combination with standard antibiotics for Clostridium difficile disease. JAMA 1994;271:1913-8 [published erratum appears in JAMA 1994;272:518].

4. Morazzoni P, Bombardelli E. Silybum marianum (Carduus marianus). Fitoterapia 1995;66:3-42 [review].