Efficacy and safety of herbal medicine (Dangguijagyag-san) for primary dysmenorrhea: study protocol for a randomized, double-blind, placebo-controlled, parallel-group, multi-center trial

Dangguijagyag-san, also known as Dangguishaoyao-san in Chinese and Toki-shakuyakui-san in Japanese, has been frequently used to treat symptoms associated with dysmenorrhea. The purpose of this trial is to evaluate the efficacy and safety of the herbal medicine, Dangguijagyag-san, relative to those of active control, Gamisoyo-san, and a placebo control for primary dysmenorrhea. This protocol details a randomized, double-blind, parallel-group, multi-center, investigator-initiated, controlled trial evaluating treatment of primary dysmenorrhea. Two hundred and forty participants will be randomly divided into one of three groups: 1) the Dangguijagyag-san experimental group (EG) (n = 105), 2) the Gamisoyo-san active control group (ACG) (n = 30), and 3) the placebo control group (PCG) (n = 105). The interventions will be administered for two menstrual cycles, and the follow-up will be carried out for the following six menstrual cycles. The primary outcomes are difference in response rates between the EG and the ACG (non-inferiority comparison) and difference in changes from baseline in average pain intensity measured by the visual analogue scale between the EG and PCG (superiority comparison). The secondary outcomes are pain scores derived from pain assessment tools (verbal multidimensional scoring system, retrospective symptom scale, and short form McGill pain questionnaire), dosage of analgesics, pattern diagnosis questionnaires, and short form 36 health survey. Adverse events and vital signs will be checked at every visit, and laboratory tests will be performed for safety evaluation. The results of this clinical trial will offer evidence for the efficacy and safety of Dangguijagyag-san for primary dysmenorrhea. Clinical Research Information Service of Korea: KCT0003005