A young reproductive‑age woman with severe lower‑abdominal pain starting one day before menstruation and lasting two days into menses, refractory to acetaminophen while taking combined oral contraceptive pills, what is the most likely diagnosis and appropriate first‑line management?

Severe Perimenstrual Dysmenorrhea Refractory to Acetaminophen

This patient most likely has primary dysmenorrhea that has failed first-line therapy with acetaminophen; she requires immediate escalation to therapeutic-dose NSAIDs (ibuprofen 600–800 mg every 6–8 hours or naproxen 440–550 mg every 12 hours) for 5–7 days during symptomatic periods, and if NSAIDs fail after 2–3 cycles, she should be evaluated for secondary causes such as endometriosis. 1

Diagnosis: Primary vs. Secondary Dysmenorrhea

• Primary dysmenorrhea is the most common cause of severe menstrual pain in young women and is defined as painful menstruation without pelvic pathology. 2
• The timing is classic: pain starting one day before menses and lasting two days into the menstrual period. 2
• Severe dysmenorrhea significantly impairs quality of life, with affected women scoring 54% on quality-of-life measures during menstruation compared to 80% during pain-free phases and 81% in controls. 3

Immediate Management: NSAID Escalation

• Acetaminophen alone is inadequate for dysmenorrhea; therapeutic-dose NSAIDs are the evidence-based first-line treatment. 1
• Begin ibuprofen 600–800 mg every 6–8 hours with food OR naproxen 440–550 mg every 12 hours for 5–7 days during symptomatic periods. 1
• Approximately 18% of patients do not respond to NSAIDs, which should trigger evaluation for secondary causes. 1
• Do not under-dose NSAIDs; use the recommended therapeutic doses from the start. 1

Addressing the Combined Oral Contraceptive Failure

• The patient is already on combined oral contraceptives (OCPs), which are commonly used but have limited evidence for endometriosis-related pain. 4, 5
• OCPs may provide initial relief for primary dysmenorrhea but are less effective than GnRH analogues for dysmenorrhea and may not prevent endometriosis progression with long-term use. 4, 5
• If NSAIDs plus OCPs fail after 2–3 cycles, consider switching to progestin-only pills (norethindrone acetate or dienogest), which have randomized controlled trial evidence for endometriosis-related pain and may be superior to combined OCPs. 4

When to Investigate for Secondary Dysmenorrhea

• Obtain transvaginal ultrasound when cramping does not improve after 2–3 menstrual cycles of appropriate NSAID therapy, when abnormal pelvic examination findings are present, or when pain patterns change abruptly. 1
• Endometriosis is the leading cause of secondary dysmenorrhea in young women and should be considered when pain persists despite NSAIDs and hormonal agents. 2
• Do not continue ineffective therapy beyond 2–3 cycles without imaging. 1
• Transvaginal ultrasound provides 82.5% sensitivity and 84.6% specificity for secondary causes, though small endometriotic implants may be missed. 6

Diagnostic Algorithm

1. Rule out pregnancy with serum β-hCG testing in all reproductive-age patients with pelvic pain. 1
2. Perform pelvic examination to assess for cervical motion tenderness, uterine tenderness, or adnexal tenderness, which would indicate possible pelvic inflammatory disease requiring empiric antibiotics. 7, 8
3. If examination is normal, escalate to therapeutic-dose NSAIDs immediately. 1
4. Reassess after 2–3 cycles; if no improvement, obtain transvaginal ultrasound. 1, 2
5. If ultrasound is non-diagnostic but symptoms persist, consider MRI pelvis (90% sensitivity and 91% specificity for endometriosis). 1

Adjunctive Non-Pharmacologic Measures

• Heat application to the abdomen/back, acupressure at LI4 and SP6 points, and topical peppermint essential oil may reduce symptoms. 1

Common Pitfalls to Avoid

• Do not delay NSAID initiation while awaiting diagnostic work-up. 1
• Never assume OCPs alone are adequate treatment for severe dysmenorrhea; NSAIDs are essential. 1, 5
• Do not omit pregnancy testing, even if contraception is reported or menses are recent. 1
• Always rule out sexually transmitted infections and chronic pelvic inflammatory disease, which may present as worsening dysmenorrhea. 1
• Recognize that approximately 10% of patients fail both NSAIDs and hormonal contraception and require further investigation. 1

Workplace Impact Counseling

• Severe dysmenorrhea is a legitimate medical condition that significantly impairs daily function and work performance. 3
• Provide documentation for workplace accommodations if needed, as this condition affects quality of life comparably to other chronic pain conditions. 3