A 28-year-old woman presents with 6 weeks of amenorrhea, right lower abdominal pain, and vaginal spotting. Transvaginal ultrasound shows an empty uterus with a 3.5 cm mass in the right adnexa. β-hCG is 8,500 mIU/mL. She is hemodynamically stable with no signs of rupture. What is the drug of choice for medical management of this ectopic pregnancy?

Explanation

## Medical Management of Unruptured Ectopic Pregnancy **Key Point:** Methotrexate is the gold-standard drug of choice for medical management of hemodynamically stable, unruptured ectopic pregnancy with β-hCG <5,000–10,000 mIU/mL and no contraindications. ### Mechanism of Action Methotrexate is a **dihydrofolate reductase inhibitor** that blocks DNA synthesis and cell division. It arrests rapidly dividing trophoblastic cells, causing regression of the ectopic pregnancy. ### Dosing Regimens | Regimen | Dose | Frequency | Best For | |---------|------|-----------|----------| | **Single-dose** | 50 mg/m² IM | Once | β-hCG <1,000; no risk factors | | **Two-dose** | 50 mg/m² IM | Days 0 & 4 | β-hCG 1,000–5,000 | | **Multi-dose** | 1 mg/kg IM | Days 1, 3, 5, 7 + folinic acid | β-hCG >5,000 | ### Eligibility Criteria for Medical Management 1. Hemodynamically stable (no rupture) 2. β-hCG <5,000–10,000 mIU/mL (higher levels: lower success rate) 3. Ectopic mass <3.5–4 cm 4. No fetal cardiac activity 5. No contraindications to methotrexate (normal renal/hepatic/hematologic function) 6. Reliable follow-up (serial β-hCG monitoring) **High-Yield:** Success rate of methotrexate is **88–96%** for β-hCG <1,000 and **70–80%** for β-hCG 1,000–5,000. ### Monitoring After Methotrexate - β-hCG on days 4 and 7 (should decline by ≥15% between days 4–7) - If β-hCG plateaus or rises → repeat dose or surgical intervention - Continue monitoring until β-hCG becomes undetectable (may take 4–6 weeks) **Clinical Pearl:** In this case, β-hCG of 8,500 is at the upper limit of medical management eligibility; single-dose methotrexate may have lower success, but multi-dose is appropriate and indicated. ### Why Not Other Agents? - **Mifepristone** (progesterone antagonist): Used adjunctively in some protocols but NOT first-line monotherapy for ectopic pregnancy - **Misoprostol** (prostaglandin analogue): No role in ectopic pregnancy; used for medical abortion of intrauterine pregnancy - **Oxytocin** (uterotonic): Contraindicated in ectopic pregnancy; causes uterine contractions but does not affect the ectopic mass [cite:Telinde's Operative Gynecology 13e Ch 12]