Metronidazole 2% Gel Versus Clindamycin 1% Gel for Moderate Acne Vulgaris

This is an investigator-initiated, parallel-group randomized controlled trial (RCT) conducted in the Department of Dermatology, Jinnah Postgraduate Medical Centre (JPMC), Karachi. After approval from the Institutional Review Board (IRB) and the College of Physicians and Surgeons Pakistan (CPSP), adults aged 18-35 years with moderate acne vulgaris, defined by a Modified Global Acne Grading System (mGAGS) score of 45-80, and not using other anti-acne therapies will be enrolled using non-probability consecutive sampling. Participants who are pregnant or lactating, have severe acne (mGAGS >80), have a known allergy to metronidazole or clindamycin, or have other dermatologic conditions affecting the face will be excluded.

Participants will be randomized in a 1:1 allocation using blocked randomization to receive either metronidazole 2% gel or clindamycin 1% gel. The assigned treatment will be applied as a thin layer twice daily (morning and night) for 12 weeks after gentle cleansing and drying of the face. Concomitant anti-acne products will be discouraged during the intervention period. Follow-up assessments will occur at weeks 4, 8, and 12. At each visit, acne severity will be assessed using mGAGS, and tolerability will be evaluated by recording local adverse effects, including erythema, itching, dryness, burning, or irritation.

The primary endpoint is treatment response at week 12, defined as a ≥50% reduction in total mGAGS score from baseline. Participants will be classified as responders (≥50% reduction) or non-responders (<50% reduction). Data will be analyzed using Statistical Package for the Social Sciences (SPSS) version 26. Categorical outcomes will be compared using the chi-square test or Fisher's exact test, and continuous variables will be compared using the independent-samples t test or Mann-Whitney U test according to data distribution. Stratified analyses will explore effect modification by age and sex. A two-sided p value ≤0.05 will be considered statistically significant.

Inclusion criteria

Adults aged 18-35 years of either sex.

Clinical diagnosis of moderate acne vulgaris, defined as a Modified Global Acne Grading System (mGAGS) score of 45-80.

Not currently using any other anti-acne treatment (topical or systemic).

Exclusion criteria

Pregnant or lactating women.

Severe acne vulgaris, defined as an mGAGS score >80.

Known hypersensitivity/allergy to metronidazole or clindamycin (or any component of the study gels).

Any other dermatologic condition affecting the face that may interfere with assessment of acne severity or treatment response.