Drug Interactions

Metronidazole (Flagyl®) Interactions

Metronidazole Drug Interactions

  • Alcohol: Metronidazole taken in combination with alcohol may produce disulfiram-like reaction - unpleasant effects such as abdominal cramps, nausea, vomiting, and flushing. Metronidazole is guessed to block the breakdown of alcohol, leading to accumulation of acetaldehyde in the blood.
    Try to avoid alcohol during treatment and for at least 3 days after.
  • Disulfiram: In a clinical trial of combined therapy with disulfiram and metronidazole in the treatment of chronic alcoholics, severe acute psychotic reactions occurred in 6 out of 29 patients.
  • Warfarin: Metronidazole inhibits the breakdown of the more potent S-isomer of warfarin. This is the pharmacologically active metabolite of the racemic parent molecule. Therefore, the activity of warfarin is enhanced by metronidazole.

Interference with Clinical Laboratory Tests:

  • Metronidazole may show negative interference with continuous flow spectrophotometry of aspartate aminotransferase (previously GOT) so that hepato-cellular damage which is detectable by raised serum AST may be missed.

Can you take Metronidazole with Amoxicillin?

Yes, it is safe to take metronidazole and amoxicillin at the same time. The combination metronidazole plus amoxicillin has been widely used in the treatment of dental infections4 and other diseases5.

Can you take Metronidazole with Ciprofloxacin (Cipro®)?

Yes. There should not be any problems taking metronidazole along with ciprofloxacin. The combination metronidazole plus ciprofloxacin is used in the treatment of Crohn's disease and mixed aerobic/anaerobic infections6.

Can you take Metronidazole with Levofloxacin (Levaquin®)?

Yes. It is safe to take metronidazole in combination with levofloxacin. Also, levofloxacin plus metronidazole is used in the the treatment of intra-abdominal infections7.

Can you take Metronidazole with Miconazole (Monistat® )?

Yes. It is safe to use metronidazole and Monistat® at the same time.

Can you take Metronidazole and Fluconazole (Diflucan®) at the same time?

Metronidazole and fluconazole don't have any interaction so they can be taken together.

Can you take Metronidazole and Ibuprofen (Advil, Motrin, Midol®) at the same time?

Yes, it is safe to take metronidazole along with ibuprofen and other NSAIDs.

Can you take Metronidazole and Tramadol (Ultram®) at the same time?

Yes, it is safe to take metronidazole and tramadol together.

Can you take Metronidazole and Prednisone at the same time?

Possible minor drug interaction. Prednisone induces the metabolism of metronidazole by liver enzymes3. Reports about other corticosteroids are lacking.

Can you take Metronidazole and Mebendazole (Vermox®) together?

One case-control study identified that concomitant use of metronidazole and mebendazole represents a risk factor for an outbreak of Stevens-Johnson syndrome/toxic epidermal necrolysis2.

Can you take Metronidazole and Albendazole (Albenza®) together?

No contraindication on concomitant use. Metronidazole plus albendazole combination seems to work synergistically for giardiasis8.

Metronidazole during Pregnancy & Lactation:
Pregnancy Risk Factor: B (no proven risk)
Although metronidazole is in the FDA category B (meaning it is unlikely to be harmful to the fetus), it should be avoided during the 1st trimester of pregnancy because of concerns about its mutagenicity.

Because of the potential for tumorigenicity, shown in mouse and rat studies, a decision should be made whether to discontinue nursing or to discontinue metronidazole, taking into account the importance of the treatment to the mother. Metronidazole is secreted in human milk in concentrations similar to those found in plasma.

See also


  • 1. U.S. FDA Metronidazole (Flagyl) Prescribing Information
  • 2. Chen KT, Twu SJ, Chang HJ, Lin RS. Outbreak of Stevens-Johnson syndrome/toxic epidermal necrolysis associated with mebendazole and metronidazole use among Filipino laborers in Taiwan. Am J Public Health. 2003 Mar;93(3):489-92. PubMed
  • 3. Eradiri O, Jamali F, Thomson ABR. Interaction of metronidazole with phenobarbital, cimetidine, prednisone, and sulfasalazine in Crohn’s disease. Biopharm Drug Dispos (1988) 9, 219– 27.
  • 4. López NJ, Socransky SS, Da Silva I, Japlit MR, Haffajee AD. Effects of metronidazole plus amoxicillin as the only therapy on the microbiological and clinical parameters of untreated chronic periodontitis. J Clin Periodontol. 2006 Sep;33(9):648-60. PubMed
  • 5. Wong WM, Huang J, Xia HH, Fung FM, et al. Low-dose rabeprazole, amoxicillin and metronidazole triple therapy for the treatment of Helicobacter pylori infection in Chinese patients. J Gastroenterol Hepatol. 2005 Jun;20(6):935-40. PubMed
  • 6. Greenbloom SL, Steinhart AH, Greenberg GR. Combination ciprofloxacin and metronidazole for active Crohn's disease. Can J Gastroenterol. 1998 Jan-Feb;12(1):53-6. PubMed
  • 7. Hermsen ED, Hovde LB, Sprandel KA, Rodvold KA, Rotschafer JC. Levofloxacin plus metronidazole administered once daily versus moxifloxacin monotherapy against a mixed infection of Escherichia coli and Bacteroides fragilis in an in vitro pharmacodynamic model. Antimicrob Agents Chemother. 2005 Feb;49(2):685-9. PubMed
  • 8. Cacopardo B, Patamia I, Bonaccorso V, Di Paola O, Bonforte S, Brancati G. Synergic effect of albendazole plus metronidazole association in the treatment of metronidazole-resistant giardiasis Clin Ter. 1995 Dec;146(12):761-7. PubMed

By HealthyStock Research Group, September 2009
Medical resources reviewed: August 2018

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