Correct Answer: C. Single-dose methotrexate injection
This is an unruptured ectopic pregnancy (6 weeks amenorrhea, positive hCG, adnexal mass, hemodynamically stable) managed medically with single-dose methotrexate. The discriminating factors are: (1) hCG <5000 IU/L (here 2800), (2) mass <3.5 cm (here 3 × 2.5 cm), (3) hemodynamic stability, and (4) no rupture. Per Indian guidelines (FOGSI, ICOG) and Harrison, single-dose methotrexate (50 mg/m² IM) is the first-line medical management for uncomplicated ectopic pregnancy meeting these criteria. Single-dose regimen is preferred over serial dosing because it has comparable efficacy (success rate ~88–95%), lower toxicity, better compliance, and lower cost—critical in Indian practice settings. The patient requires close follow-up with serial hCG monitoring (days 4 and 7; should decline by ≥15% by day 7). Leucovorin rescue is NOT needed with single-dose methotrexate because the lower cumulative dose avoids significant bone marrow and hepatic toxicity. This regimen preserves tubal integrity, crucial for future fertility.
Why the other options are wrong
A. Serial methotrexate + leucovorin rescue — Serial methotrexate (days 0, 4, 8 with leucovorin rescue on days 1, 5, 9) is reserved for hCG >5000 IU/L or when single-dose fails. This patient's hCG is 2800—well below the threshold. Serial dosing increases cumulative toxicity, cost, and requires more clinic visits; it is overtreatment for uncomplicated early ectopic pregnancy. Leucovorin rescue is unnecessary with single-dose regimens. B. Salpingectomy — Surgical management (salpingectomy or salpingostomy) is indicated for ruptured ectopic pregnancy, hemodynamic instability, contraindications to methotrexate, or failed medical management. This patient is hemodynamically stable with no signs of rupture (no acute abdomen, no shock). Medical management is preferred to preserve tubal function and fertility—critical in Indian women of reproductive age. Surgery is reserved as second-line therapy. D. Oral methotrexate — Oral methotrexate has poor bioavailability and unpredictable absorption, leading to subtherapeutic levels and higher failure rates (~20–30%). The intramuscular route ensures reliable drug delivery and better outcomes. Oral administration is not recommended by FOGSI or international guidelines (ACOG, RCOG) for ectopic pregnancy management and is a common NBE trap confusing route of administration.
High-Yield Facts
- Single-dose methotrexate (50 mg/m² IM) is first-line medical management for unruptured ectopic pregnancy with hCG <5000 IU/L and mass <3.5 cm.
- Success rate of single-dose methotrexate is 88–95%; serial dosing is reserved for hCG >5000 IU/L or single-dose failure.
- Leucovorin rescue is NOT used with single-dose methotrexate because cumulative toxicity is minimal; it is only given with serial methotrexate regimens.
- Serial hCG monitoring on days 4 and 7 is mandatory; hCG should decline by ≥15% by day 7 to predict success.
- Hemodynamic stability + no rupture signs = medical management eligible; surgery (salpingectomy) is reserved for rupture, instability, or failed medical therapy.
- Methotrexate is contraindicated in active pulmonary/renal disease, immunodeficiency, blood dyscrasias, and active infection; baseline CBC, LFT, renal function required.
Mnemonics
HEMODYNAMIC STABLE = MEDICAL (HSM) Hemodynamic stable → Methotrexate (medical). Hemodynamic unstable → Surgery (salpingectomy). Use this at the bedside to decide ectopic pregnancy management in seconds. hCG <5000 = SINGLE-DOSE (5S rule) hCG <5000 → Single-dose methotrexate. hCG >5000 → Serial-dose methotrexate. Memorize the 5000 cutoff—it's the most tested threshold in NEET PG. MTX ROUTE: IM > Oral (Route Rule) Intramuscular methotrexate is standard (reliable absorption). Oral methotrexate is NOT recommended (poor bioavailability, high failure). Always choose IM in exams.
NBE Trap
NBE commonly pairs "serial methotrexate + leucovorin" with early ectopic pregnancy to trap students who memorize methotrexate without understanding the hCG threshold and regimen selection. The trap is confusing "methotrexate is the drug" with "which methotrexate regimen"—single-dose vs. serial is the discriminator.
Clinical Pearl
In Indian primary health centers and district hospitals, single-dose methotrexate is preferred because it requires only one injection, one follow-up visit (day 7 hCG), and costs ~₹200–400—making it accessible to resource-limited settings. Serial dosing demands 3 injections and 3 clinic visits, increasing dropout and cost; reserve it only for high hCG cases where single-dose is likely to fail.
_Reference: DC Dutta's Textbook of Obstetrics (8th ed.) Ch. 10 (Ectopic Pregnancy); FOGSI Guidelines on Management of Ectopic Pregnancy; Harrison Ch. 306_