Minocycline: Everything you need to know about this antibiotic used in the treatment of rosacea.

Minocycline is a broad-spectrum antibiotic belonging to the tetracycline family. It is used to treat a variety of infections caused by bacteria, including acne and the papulopustular rosacea. It is a second-generation tetracycline, similar to doxycycline. In terms of papulopustular rosacea, a minocycline treatment allows for the reduction in the number of papules and pustules, which visibly improves the appearance and texture of the skin. Minocycline is also associated with a reduction in redness, contributing to an improved quality of life for patients suffering from rosacea.

From a mechanistic standpoint, minocycline is a bacterial protein translation inhibitor. This substance has the ability to cross the bacterial wall, either through porins or by diffusion across the phospholipid layer, before attaching to the 30S subunit of the ribosomes. Minocycline thus halts protein synthesis. Deprived of the proteins essential for their growth, the bacteria cease to multiply. This antibacterial property of minocycline is particularly interesting in the case of papulopustular rosacea, a dermatosis which is believed to be influenced by the multiplication of certain microorganisms on the skin surface.

Minocycline also acts on the inflammatory symptoms of rosacea by inhibiting the production of pro-inflammatory cytokines such as interleukins-1 and 6 (IL-1 and IL-6) and tumor necrosis factor (TNF-α) by immune cells. Minocycline can also prevent the degradation of collagen by collagenase-type enzymes, thus reducing tissue damage associated with inflammation. Finally, this substance can modulate certain intracellular signaling pathways, such as the MAPK and NF-κB, playing a role in the regulation of the expression of genes involved in inflammation processes.

Note : Minocycline can cause photosensitization of the skin. Therefore, it is recommended to apply daily sun protection throughout the treatment. Moreover, it is good to know that minocycline is not advised for pregnant women during the last six months of pregnancy and for children under eight years old as it could lead to permanent discoloration of the teeth.

Today, minocycline is an antibiotic predominantly used orally to alleviate the symptoms of acne or papulopustular rosacea. A recent study involving 80 patients with papulopustular rosacea highlighted the benefits of administering this substance and compared its effectiveness to doxycycline, another antibiotic that can be prescribed to combat this skin condition. For this purpose, the 80 volunteers were divided into 2 equal groups of 40 people. Individuals in the first group received 100 mg of minocycline per day for 16 weeks, while those in the second group were given 40 mg of doxycycline.

Following the treatment, a symptom improvement of more than 50% was measured in 40% of the "minocycline" group and in 36% of the patients in the "doxycycline" group. Furthermore, 35% of the patients in the "minocycline" group noticed an "excellent improvement", compared to 36% of those in the "doxycycline" group. No major adverse effects were reported. Minocycline, having a less favorable benefit/risk ratio than doxycycline, could thus be an interesting treatment alternative for people suffering from papulopustular rosacea who cannot take doxycycline, for whatever reason.

Less common, the topical application of minocycline could also be of interest in cases of papulopustular rosacea. This is at least what two identical clinical studies conducted in parallel by STUART and his team suggest. The first involved 669 patients with papulopustular rosacea and the second 718. In each study, the patients were divided into two groups: one group received a cream with 1.5% minocycline (437 people in the first study and 479 in the second) and the other received the same cream without minocycline. After 12 weeks of daily application, very good results were obtained in both studies, showing that topical minocycline could be effective in combating papulopustular rosacea.

Indeed, in the first study, scientists observed a 64% reduction in inflammatory lesions in the "minocycline" group. In the second, the measured decrease was 61%. These two reductions were significantly greater than those in the "placebo" groups. Significant decreases in erythema, visibility of telangiectasias, and patients' burning sensations were also recorded. Moreover, the tested cream was very well tolerated. These clinical studies thus provide hope for the potential of topical minocycline in treating papulopustular rosacea.

• RAMAMURTHY N. & al. Tetracyclines inhibit tissue collagenases. Effects of ingested low-dose and local delivery systems. Journal of Periodontology (1985).

• VIDAL. Substance Active Minocycline (2013).

• NIEUWENBURG S. & al. DOMINO, doxycycline 40 mg vs. minocycline 100 mg in the treatment of rosacea: a randomized, single‐blinded, noninferiority trial, comparing efficacy and safety. British Journal of Dermatology (2017).

• STUART I. & al. Minocycline 1.5% foam for the topical treatment of moderate to severe papulopustular rosacea: Results of 2 phase 3, randomized, clinical trials. Journal of the American Academy of Dermatology (2020).