RESEARCH QUESTION/RATIONALE Hidradenitis suppurativa is a chronic, auto-inflammatory skin disease characterized by painful inflammatory nodules, abscesses, and sinus tract formation. A pilot study with metformin in HS found improvement of the disease in 18 out of 25 patients, with minimal side effects. Therefore, the primary objective of this study is to determine the clinical efficacy of doxycycline and metformin compared with the standard treatment with doxycycline alone after 24 weeks of treatment.
HYPOTHESIS We hypothesize that combined treatment with metformin and doxycycline is more effective compared with doxycycline monotherapy.
STUDY DESIGN A multicentre randomised controlled superiority trial.
STUDY POPULATION The study population is comprised of adult patients with mild/ moderate Hidradentis Suppurativa according to the HS-Physician Global Assessment and refined Hurley staging.
INTERVENTION(& COMPARATOR) Intervention treatment consists of a combinaiton of doxycycline 100mg daily and metformin; up-titrated from 500mg daily in week 1, to 1000mg a day in week 2, to 1500mg a day from week 3 through to week 24. This will be compared with doxycycline monotherapy 100mg a day for 24 weeks.
OUTCOME MEASURES The primary outcome measure is the validated, dynamic, and internationally accepted, open-end International Hidradenitis Suppurativa Severity Score System (IHS4) after 24 weeks of treatment. Secondary outcomes include HiSCR, NRS skin-related pain, quality of life after 12 and 24 weeks of treatment.
SAMPLE SIZE/DATA ANALYSIS The sample size is 31 patients per arm, calculated for a superiority design with a power of 80%, alpha level of 0.05, and 10% drop-out. The primary outcome will be analysed using a unpaired T-test, according to the intention-to-treat principle.