When presented with a case of rosacea, many dermatologists will reach out for metronidazole. The trust in this drug has been built over decades of scientific evidence proving its safety and effectiveness. If you’re considering using this treatment, here are some facts you should know about metronidazole.
What is metronidazole?
Metronidazole is primarily used as an antibiotic and antiprotozoal medication. It kills off microorganisms by messing with their DNA structure, causing derangements in the normal processes of their targets. It can come in oral, topical, or injectable forms, and has been used for everything from enteritis to vaginosis, amoebiasis to trichomoniasis, surgical prophylaxis, among others.
How does metronidazole work against rosacea?
Funnily enough, we aren’t exactly sure. Metronidazole is a first line therapy for rosacea and is FDA-approved for this purpose, but the question on how an antibacterial/antiprotozoal works against a condition where microorganisms are not the root cause is still not quite clear.
Rosacea is a complex disease, but experts agree that a dysregulated immune system is one of the major factors involved in its development. Indeed, the symptoms of rosacea, such as redness, pustule and papule development, and dryness of the skin, are all hallmarks of an immune response in the skin.
It would seem that metronidazole is a potent antioxidant. Reactive oxygen species (ROS) are produced by a variety of mechanisms when an immune response is mounted. While it’s good that our bodies are capable of fighting invaders and protecting ourselves, the accumulation of ROS causes unwanted collateral damage in the process.
That’s where metronidazole comes in. A study by Akamatsu et al. (1990) found the metronidazole was able to curb the ROS generated by activated neutrophils. Another study by Narayanan et al. (2007) found that metronidazole is great at scavenging ROS, sequestering them and preventing the damage they cause to the rest of the body.
Is metronidazole an effective rosacea treatment?
Metronidazole has long been proven to minimize erythema or redness, papules, and pustules. Clinical trials in the 80s and 90s were promising, with metronidazole improving 68-96% of rosacea patients involved in the studies (Schmadel and McEvoy, 1990).
Since its entry into the market, metronidazole has continued to live up to the hype. A community-based study involving 580 rosacea patients confirmed that twice daily application of metronidazole is effective in actual practice (Campbell, 2005). A review of literature found that moderate to severe cases of rosacea improved with metronidazole treatment over a period of 7-12 weeks, with the number of inflammatory papules and pustules decreasing by 48-65.1% (McClellan and Noble, 2000). It is safe enough to use as maintenance medication to prevent remission of rosacea flare-ups (Dahl et al., 1998).
Other rosacea treatment options have since emerged, but metronidazole continues to hold its own. Together with more recently introduced azelaic acid, metronidazole is considered a first-line therapy for mild to moderate papulopustular rosacea (del Rosso, 2002; van Zuuren et al., 2007).
What are the side effects of metronidazole?
The most common side effects of topical metronidazole is dryness, stinging, and itchiness at the site of application. These are usually noted at the start of therapy, and eventually go away with continued use (McClellan and Noble, 2000). When used according to the dermatologist’s instructions, topical metronidazole will not be appreciably absorbed into circulation and cause side effects associated with oral or intravenous formulations of the drug.
Metronidazole should not be used by pregnant women. Lactating women should get their doctor’s advice before using this drug.
While metronidazole does not cause photosensitization, sun protection is still recommended. UV rays are known to decrease the effectiveness of this drug, so you should be staying out of the sun and avoiding tanning beds while under therapy.
What should I know before starting metronidazole?
Metronidazole works its magic best on papulopustular rosacea, and has been used for ocular rosacea (Barnhorst et al., 1996). Unfortunately, it is not effective on telangiectasia.
It is also important to manage your expectations about this drug. It is palliative, not curative--that is, it’s not something you do for a couple of months and you’re free of rosacea forever. Studies show that the rosacea relapse occurs 6 months or less after stopping metronidazole therapy (Dahl et al., 1998). So to continue reaping this drug’s benefits, you will need to continue using it.
Metronidazole is not an overnight drug. It takes around 3-4 months of continued use to be able to see improvement. So trust the process, consult your dermatologist, and you will find out if you are one of thousands of rosacea patients who have found their holy grail in metronidazole.
This content is for general information only and is not a substitute for medical advice.
References:
Akamatsu H, Oguchi M, Nishijima S, et al. The inhibition of free radical generation by human neutrophils through the synergistic effects of metronidazole with palmitoleic acid: a possible mechanism of action of metronidazole in rosacea and acne. Arch Dermatol Res. 1990;282:449-454.
Campbell J. 2005. Treatment of moderate to severe rosacea with topical metronidazole 0.75% gel: A meta-analysis. Journal of the American Academy of Dermatology. Poster Discussion Session 495—Pediatrics, 5(3):171. https://doi.org/10.1016/j.jaad.2004.10.692
Dahl MV, Katz HI, Krueger GG, et al. Topical Metronidazole Maintains Remissions of Rosacea. Arch Dermatol. 1998;134(6):679–683. doi:10.1001/archderm.134.6.679
McClellan, K. J., & Noble, S. (2000). Topical metronidazole. A review of its use in rosacea. American journal of clinical dermatology, 1(3), 191–199. https://doi.org/10.2165/00128071-200001030-00007
Sabrina Narayanan, Andreas Hùnerbein, Melkamu Getie, Andreas Jäckel, Reinhard H H Neubert, Scavenging properties of metronidazole on free oxygen radicals in a skin lipid model system, Journal of Pharmacy and Pharmacology, Volume 59, Issue 8, August 2007, Pages 1125–1130, https://doi.org/10.1211/jpp.59.8.0010
Schmadel, L. K., & McEvoy, G. K. (1990). Topical metronidazole: a new therapy for rosacea. Clinical pharmacy, 9(2), 94–101.
van Zuuren, E. J., Gupta, A. K., Gover, M. D., Graber, M., & Hollis, S. (2007). Systematic review of rosacea treatments. Journal of the American Academy of Dermatology, 56(1), 107–115. https://doi.org/10.1016/j.jaad.2006.04.084
Weir CB, Le JK. Metronidazole. [Updated 2022 Apr 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539728/
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