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 all sorts of infections caused by bacteria, including acne and the papulopustular rosacea. It is a second-generation tetracycline, like the doxycycline. In terms of papulopustular rosacea, a treatment with minocycline allows to reduce 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 a better quality of life for patients suffering from rosacea.

From a mechanistic perspective, 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 itself 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 tumour 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 signalling pathways, such as the MAPK and NF-κB pathways, playing a role in the regulation of the expression of genes involved in inflammation processes.

Note : Minocycline can cause photosensitisation 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 children under eight years old as it could lead to permanent discolouration of the teeth.

Today, minocycline is an antibiotic predominantly administered orally to alleviate the symptoms of acne or papulopustular rosacea. A recent study involving 80 patients suffering from 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 individuals. The 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 over 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 reported an "excellent improvement", compared to 36% of those in the "doxycycline" group. No major adverse effects were reported. Minocycline, having a less favourable benefit/risk ratio than doxycycline, could thus be an interesting treatment alternative for individuals 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 suffering from 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 had the same cream without minocycline. After 12 weeks of daily application, very good results were obtained in both studies and showed that topical application of 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 reductions in erythema, visibility of telangiectasias, and patients' burning sensations were also recorded. Furthermore, the cream tested 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).