Primary Dysmenorrhea
A 15-year-old girl has crampy lower abdominal pain beginning a few hours before each period and lasting two days for the past year. Menarche was at 13 years and cycles are regular. She is not sexually active. Abdominal and pelvic examinations are normal. Which of the following is the most appropriate initial treatment?
- A.Combined estrogen-progestin oral contraceptive
- B.Oral naproxen started at pain onsetCorrect
- C.Cervical dilatation under anesthesia
- D.Oral danazol for six months
Explanation
Regular cycles, pain that starts with menses and resolves within two days, onset within a few years of menarche, and a normal pelvic examination define primary dysmenorrhea. NSAIDs are first-line therapy. Endometrial prostaglandins, particularly PGF2-alpha, are released as the corpus luteum regresses and progesterone falls; they trigger high-amplitude uterine contractions, uterine ischemia, and pain. NSAIDs inhibit cyclooxygenase and cut prostaglandin production at its source, so they are most effective when started at or just before pain onset rather than after cramps peak. Naproxen, ibuprofen, and mefenamic acid all work; effect is usually apparent within one or two cycles. Combined oral contraceptives are effective second-line therapy by thinning the endometrium and suppressing ovulation, and are preferred when contraception is also desired or NSAIDs fail after two to three cycles. Cervical dilatation has no role and carries risks of perforation and cervical incompetence. Danazol is an androgenic agent used for refractory endometriosis and causes hirsutism, acne, and dyslipidemia, making it inappropriate as initial therapy in an adolescent. Failure of NSAIDs plus hormonal therapy after three to six months should prompt evaluation for endometriosis or an obstructive müllerian anomaly.
Why each option
- A.
- Effective second-line therapy that thins the endometrium and suppresses ovulation; chosen when NSAIDs fail or contraception is also wanted.
- B.
- Correct. NSAIDs block cyclooxygenase-mediated prostaglandin synthesis and are first-line for primary dysmenorrhea, ideally started at or just before pain onset.
- C.
- Cervical dilatation is obsolete for dysmenorrhea and risks uterine perforation and cervical incompetence.
- D.
- Danazol is reserved for refractory endometriosis and causes androgenic side effects unacceptable as initial adolescent therapy.
Reference: ACOG Committee Opinion No. 760, Dysmenorrhea and Endometriosis in the Adolescent, reaffirmed 2023
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