Acupuncture for Primary Dysmenorrhea: Meta-Analyses Confirm Clinically Relevant Reduction in Menstrual Pain

Primary dysmenorrhea — cyclic menstrual pelvic pain without identifiable pelvic pathology — is the most common gynecologic complaint among adolescents and women of reproductive age, with prevalence estimated between 50% and 90% and direct impact on school and work absenteeism. The first-line treatment recommended by guidelines (ACOG, RCOG) is nonsteroidal anti-inflammatory drugs (NSAIDs), followed by combined hormonal contraceptives. Even só, a significant portion of women presents unsatisfactory response, gastric intolerance, or contraindication to NSAIDs — opening space for evidence-based adjuvant therapies, among which acupuncture has been consolidated.

What the Meta-Analyses Show

The consolidated findings point to a clinically relevant reduction in pain intensity in the acupuncture group compared with sham, with a moderate-to-large effect magnitude. When compared directly with NSAIDs in head-to-head trials, acupuncture showed comparable analgesic efficacy, with the advantage of a safety profile — lower incidence of gastrointestinal complaints, no bleeding risk, and no contraindications in patients with ASA-sensitive asthma or peptic ulcer disease. The benefits are maintained over multiple consecutive menstrual cycles and tend to increase with continuity of treatment.

Mechanisms of Analgesia in Menstrual Pain

The pain of primary dysmenorrhea is mediated mainly by prostaglandins (PGF2α and PGE2) derived from the endometrium, which induce ischemic myometrial contractions. Acupuncture acts at multiple levels: reduction of inflammatory markers and circulating prostaglandins, central pain modulation through the release of endorphins and enkephalins in the central nervous system, regulation of autonomic tone (with parasympathetic increase and sympathetic attenuation), and modulation of the hypothalamic–pituitary–ovarian axis in neuroendocrine patterns synchronized with the menstrual cycle. In neuroimaging studies, stimulation of SP-6 and CV-4 modulates the salience network and the anterior cingulate córtex — central regions in the processing of visceral pain.

Positioning in Guidelines

Although Western gynecologic guidelines do not yet position acupuncture as a first-line therapy, the accumulated literature already justifies its inclusion as a second- or third-line option in patients with unsatisfactory response, intolerance, or contraindication to NSAIDs and combined hormonal contraceptives. In adolescents — a population in which prolonged exposure to NSAIDs and hormones is avoided — acupuncture offers a particularly attractive risk–benefit profile.