Dysmenorrhoea Management
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Direct answer
NSAIDs started at the first cramp relieve primary dysmenorrhoea in most women — mefenamic acid 500 mg thrice daily or ibuprofen 400 mg three to four times daily after food — because the pain is prostaglandin-driven myometrial ischaemia in an otherwise normal pelvis, classically beginning within hours of menarche onset of ovulatory cycles, spasmodic, peaking on the first one to two days of bleeding, and easing with age and parity. Combined oral contraceptives (or the patch or ring) are the second-line suppression, working by thinning endometrium and shrinking prostaglandin production; the levonorgestrel intrauterine system serves when contraception is also wanted. Secondary (congestive) dysmenorrhoea — pain with a pelvic cause such as endometriosis, adenomyosis, fibroids, copper IUD use or chronic pelvic infection — begins years after menarche, worsens rather than improves, and is investigated with transvaginal ultrasound (and laparoscopy when endometriosis is suspected despite normal imaging) rather than endlessly escalated analgesia; treatment is of the cause. The clinical filter worth memorising: dysmenorrhoea that fails NSAIDs, starts in the twenties, or accompanies dyspareunia, heavy bleeding or infertility is secondary until proven otherwise.
What you must remember
- Primary dysmenorrhoea: spasmodic, suprapubic, radiating to back and thighs, starting with menstruation (or just before), first one to two days worst, with nausea, vomiting, headache or diarrhoea; begins within 6-12 months of menarche as cycles become ovulatory; pelvic examination and ultrasound are normal.
- Mechanism: excess prostaglandins (PGF2 alpha chiefly) drive myometrial hypercontractility and basal artery vasoconstriction — uterine muscle angina, which is why NSAIDs (prostaglandin synthetase inhibitors) outperform plain analgesics.
- Drug doses: mefenamic acid 500 mg thrice daily, ibuprofen 400 mg three to four times daily, naproxen 500 mg initially then 250 mg every 6-8 hours — started at pain onset or the day before, with food; paracetamol alone is weaker.
- Hormonal suppression: combined oral contraceptives (also easing heavy bleeding and giving contraception); levonorgestrel-IUS especially with adenomyosis or fibroids; continuous or cyclical regimens both used.
- Non-drug measures: topical heat (as effective as ibuprofen in some trials — a viva favourite), exercise, transcutaneous electrical nerve stimulation, and reassurance that pain improves after a pregnancy in many women.
- Secondary causes checklist: endometriosis (cyclical worsening pain, deep dyspareunia, dyschezia), adenomyosis (bulky tender uterus plus heavy bleeding), submucous fibroids (heavy periods), copper IUD (cramping in first months), chronic pelvic inflammatory disease with tubo-ovarian mass, and outflow obstruction in the young (transverse vaginal septum, imperforate hymen — presenting as primary dysmenorrhoea with a haematocolpos).
- Investigation pathway: history and examination first, transvaginal ultrasound next (adenomyosis, fibroids, endometrioma), then MRI for deep disease and laparoscopy with histology as the definitive endometriosis test; tumour markers are not for dysmenorrhoea.
- Red flags demanding fast track: pain severe enough to miss school or work monthly despite NSAIDs, new-onset pain after 25, postcoital bleeding, or a palpable mass — the examination expects escalation, not repeat prescriptions.
Sorting primary from secondary pain
Two teenagers sit in clinic. The first, 16, has had cramps since six months after menarche, worst on day one, relieved partly by ibuprofen, normal examination and scan. Her plan is confident: mefenamic acid 500 mg at onset thrice daily for two days, heat pad, review — with a combined pill if pain or acne tips the balance; the pattern is unmistakably primary, so she is managed entirely at first visit.
The second, 19, began her menses at 12 painlessly and now misses college two days a month; pain is deep, bilateral, worst at the tail end of bleeding, with painful intercourse in the preceding months. This timeline — late onset, worsening trajectory — is the secondary signature. Transvaginal ultrasound shows a 3 cm endometrioma with a fixed retroverted uterus: endometriosis, joining that pathway — hormonal suppression now, fertility planning later. The third pattern belongs to a 13-year-old with monthly severe cramps and amenorrhoea — the adolescent with an outflow obstruction, where the "dysmenorrhoea" is uterus contracting against a haematocolpos: examination under anaesthesia and incision of the obstruction, not analgesics. Same symptom, three engines, three answers — the sorting logic is the examinable skill.
Frequently asked questions
Why do NSAIDs work better than paracetamol in primary dysmenorrhoea?
The pain is prostaglandin-mediated myometrial ischaemia, and NSAIDs inhibit prostaglandin synthesis at the source, unlike paracetamol's central action.
What features suggest secondary rather than primary dysmenorrhoea?
Onset years after menarche, progressive worsening, pain lasting beyond the first days of flow, deep dyspareunia, heavy bleeding, infertility or an abnormal examination — investigate with ultrasound and laparoscopy.
Which hormonal options treat dysmenorrhoea?
Combined oral contraceptives as the classic choice, and the levonorgestrel intrauterine system for adenomyosis- or fibroid-related pain with contraception needs.
What is the first-line treatment of primary dysmenorrhoea?
NSAIDs such as mefenamic acid 500 mg thrice daily or ibuprofen 400 mg three to four times daily, started at pain onset, with heat and reassurance.
Which cause must be excluded in an adolescent with severe cyclical pain and primary amenorrhoea?
Outflow tract obstruction — imperforate hymen or transverse vaginal septum causing haematocolpos, which needs surgical correction rather than analgesia.