Metronidazole (Flagyl) vs. azelaic acid (Finacea) similarities and differences

What is Metronidazole? What is Azelaic Acid?

Metronidazole is an antibiotic used to treat acne rosacea, Giardia infections of the small intestine, amebic liver abscess, amebic dysentery (infection of the colon causing bloody diarrhea), bacterial vaginosis, trichomonas vaginal infections, carriers of trichomonas (both sexual partners) who do not have symptoms of infection, abscesses (in the pelvis, liver, abdomen, and brain, Helicobacter pylori (H. pylori), C. difficile, and metronidazole vaginal gel is used to treat bacterial vaginosis.

Azelaic acid is a topical (applied to the skin) medication used for treating acne. Azelaic acid may work as an antibacterial agent that blocks protein synthesis and therefore growth of Propionibacterium acnes and other bacteria on the surface of the skin that are associated with the development of acne. It may also inhibit follicular keratinization, which prevents development of acne lesions.


Acne is the result of an allergy. See Answer

What are the side effects of metronidazole (Flagyl) and azelaic acid (Finacea)?


Flagyl is a useful antibiotic and is generally well tolerated with appropriate use.

The most common and minor side effects include:

Side effects that are uncomfortable, but may become serious include:

Serious side effects of Flagyl are rare and the drug should be stopped if these symptoms appear:

Azelaic acid

Common side effects include:

  • Burning
  • Stinging
  • Tingling

Other side effects include:

Other less common side effects include:

What is the dosage of metronidazole (Flagyl) vs. azelaic acid (Finacea)?


  • Metronidazole may be taken orally with or without food.
  • In the hospital, metronidazole can be administered intravenously to treat serious infections.
  • The liver is primarily responsible for eliminating metronidazole from the body, and doses may need to be reduced in patients with liver disease and abnormal liver function.

Azelaic acid

  • A thin layer of azelaic acid should be applied and massaged into the affected areas of the face every 12 hours.

What drugs interact with metronidazole (Flagyl) and azelaic acid (Finacea)?


  • Alcohol should be avoided because metronidazole and alcohol together can cause severe nausea, vomiting, cramps, flushing, and headache.
  • Metronidazole can increase the blood thinning effects of warfarin (Coumadin, Jantoven) and increase the risk of bleeding probably by reducing the breakdown of warfarin.
  • Cimetidine (Tagamet) increases blood levels of metronidazole while cholestyramine (Questran, Questran Light) reduces blood levels of metronidazole by reducing its absorption.
  • Metronidazole should not be combined with amprenavir (Agenerase) for treating human immunodeficiency disease (infection with HIV) because amprenavir contains propylene glycol.
  • Metronidazole blocks the breakdown of propylene glycol in the liver leading to accumulation of propylene glycol in blood. Accumulation of propylene glycol could cause seizures, increased heart rate, and lead to kidney failure.
  • Metronidazole increases the blood levels of carbamazepine (Tegretol, Tegretol XR, Equetro, Carbatrol), lithium (Eskalith, Lithobid) and cyclosporine though unknown mechanisms. Serious reactions may occur if these drugs are taken with metronidazole.

Azelaic acid

There are no drug interactions listed for this azelaic acid.


Skin Health: How to Get Clear Skin See Slideshow

Are metronidazole (Flagyl) and azelaic acid (Finacea) safe to use while pregnant or breastfeeding?


  • Metronidazole is not used in early pregnancy because of potential adverse effects on the fetus.
  • Metronidazole is excreted in breast milk. Females who are nursing, because of potential adverse effects on the newborn, should not use metronidazole.

Azelaic acid

  • The safety azelaic acid has not been evaluated. It is not known whether azelaic acid is excreted in human milk. However, laboratory experiments suggest that the small amount of azelaic acid that is absorbed into the body may be excreted in human milk at very low concentrations that may not be significant.

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Metronidazole and azelaic acid are antibiotics used to treat acne. Brand names for metronidazole include Flagyl and Flagyl ER and brand names for azelaic acid include Finacea and Azelex. A difference is metronidazole is taken orally and azelaic acid is used topically (on the skin).

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