Also indexed as: Flagyl, MetroCream, MetroGel, MetroLotion,
Noritate, Protostat
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.
Summary of
Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem
contradictory. For clarification, read the full article for details about the summarized
interactions.
 May Be Beneficial: Side effect
reduction/prevention—Taking these supplements may help reduce the likelihood and/or
severity of a potential side effect caused by the medication. |
Saccharomyces boulardii (for Clostridium
difficile only)
|
| May Be Beneficial: Supportive
interaction—Taking these supplements may support or otherwise help your medication
work better. |
Saccharomyces boulardii (for Clostridium
difficile only)
|
Check: Other—Before taking any of these supplements or eating any of
these foods with your medication, read this article in full for details. |
Diosmin
Milk thistle
|
| Depletion or interference |
None known
|
| Reduced drug
absorption/bioavailability |
None known
|
| Adverse interaction |
None known
|
An asterisk (*) next to an item in the summary indicates that the
interaction is supported only by weak, fragmentary, and/or contradictory scientific
evidence.
Interactions with Dietary Supplements
Diosmin
Diosmin is a flavonoid used to treat hemorrhoids and vein disorders. In a study of healthy
male volunteers who took 800 mg of metronidazole, pretreatment with 500 mg of diosmin per day
for nine days increased blood levels of metronidazole by 24%.1 Diosmin appears to
increase the availability of metronidazole by inhibiting the enzyme that normally breaks it
down. The results of this study suggest that taking diosmin may increase both the
effectiveness and toxicity of metronidazole.
Saccharomyces
boulardii
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.2 3 4
Interactions with Herbs
Milk
thistle (Silybum marianum)
Milk thistle has been reported to protect the liver from harm caused by some prescription
drugs.5 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.
Interactions with Foods and Other Compounds
Food
Metronidazole should be taken with food to avoid stomach upset.
Alcohol
Alcohol may interact with metronidazole, causing facial flushing, headache, light-headedness,
nausea, breathlessness, and other symptoms.6 Vinegar typically contains small
amounts of alcohol and should be avoided during metronidazole therapy. People should read all
product labels carefully for alcohol content and should avoid alcohol-containing products
during metronidazole therapy.
References:1. Rajnarayana K, Reddy MS, Krishna DR. Diosmin pretreatment affects
bioavailability of metronidazole. Eur J Clin Pharmacol 2003;58:803–7.
2. Surawicz CM, McFarland LV. Pseudomembranous colitis: causes and cures.
Digestion 1999;60:91–100 [review].
3. Eddy JT, Stamatakis MK, Makela EH. Saccharomyces boulardii for the
treatment of Clostridium difficile-associated colitis. Ann Pharmacother
1997;31:919–21.
4. 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].
5. Morazzoni P, Bombardelli E. Silybum marianum (Carduus
marianus). Fitoterapia 1995;66:3–42 [review].
6. Threlkeld DS, ed. Systemic Anti-Infectives, Metronidazole. In
Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Nov 1992,
353a–3e.