Metronidazole (topical)

Tolerability and safety

Irritation potential

Low

Allergen risk

Low

Pregnancy

Caution

About this ingredient

Topical metronidazole (Metronidazole, brands Metrogel, Rozex, Rosalox) is a synthetic imidazole antibiotic, first-line for rosacea. An active member of the 5-nitroimidazole family. Mechanism. Systemically suppresses anaerobic bacteria by damaging their DNA. Topical antimicrobial effect is minimal – the main action is anti-inflammatory: suppresses neutrophil migration, reduces reactive oxygen species production and arachidonic acid metabolism. Where applied. 0.75% gel and cream (Metrogel, Rozex), 1% cream (Noritate). Main indication – papulopustular rosacea. Prescription-only in Spain, listed by AEMPS as ATC D06BX01. In Spain in Rozex, Noritate, generic Metronidazol Mylan. Evidence base. The van Zuuren meta-analysis (Cochrane 2015, updated 2019) included 28 topical metronidazole RCTs in rosacea – 50–70% papule and pustule reduction over 8–12 weeks. Efficacy comparable to topical azelaic acid 15%, lower than ivermectin 1%. NICE 2024 and AAD 2023 recommend metronidazole as first-line for papulopustular rosacea. Safety. Well tolerated. Irritation, dryness, mild burning in 10–15% of patients in the first 2 weeks. Contact allergies are rare (<1%). Does not photosensitize. Non-comedogenic. Pregnancy and lactation – use with caution. FDA Category B. Topical use in the first trimester per AAD 2023 and SEGO 2023 is acceptable if needed – systemic absorption is minimal (<1%). In the second and third trimesters – safe. In lactation – safe; do not apply on the breast immediately before feeding. Oral form controversy. Oral metronidazole for rosacea is used in short courses (3–4 weeks) for severe forms. Long-term use is not recommended due to neurotoxicity risk and alcohol interaction. Topical is the maintenance therapy form. Compatibility. Combines with azelaic acid, niacinamide, hypoallergenic moisturizers. Does not combine with aggressive cleansers and acids – risk of rosacea flare.

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