Whether the transient hair shedding phase exist after minoxidil treatment and does it predict treatment efficacy? A retrospective study in androgenetic alopecia patients.

Purpose: Minoxidil is a routinely used drug in treating multiple hair disorders. This study aimed to investigate the facticity of the temporal increase in the hair shedding amount after topical use of minoxidil.

Materials and methods: We selected 49 patients who used 2% or 5% minoxidil topically to treat androgenetic alopecia for 24 weeks. The amount of hair shedding was recorded every four weeks before and after the treatment. The BASP classification and trichoscopy test results were also recorded before and after the treatment. The relative amount of hair shedding (RAHS) was defined as the recorded number of hair shedding after normalization. The correlation between the maximum RAHS (MRAHS) and the sulfotransferase activity as well as the therapeutic effect was calculated.

Results: A temporary increase in the amount of hair shedding was detected in the first 12 weeks. This increase has a longer duration in patients treated with 2% minoxidil compared to 5%. Its severity was correlated with the improvement of trichoscopy tests only in patients with 5% minoxidil but not in 2%. However, both patients in the 2% and 5% minoxidil groups had a significant association between the MRAHS and the improvement in BASP classification.

Conclusion: The amount of hair shedding increases temporarily after the topical minoxidil use, the level of which is a potential treatment efficacy.