A woman treated with single-dose methotrexate (50 mg/m²) for an unruptured ectopic (beta-hCG 2,100 IU/L) has a 5% drop in hCG from day 1 to day 4, and a 10% drop from day 4 to day 7. The correct interpretation and management is:
- A Treatment is successful; continue weekly hCG monitoring until undetectable
- B The response is inadequate; a second dose of methotrexate should be given on day 7 ✓
- C Treatment failure; immediate surgical intervention is required
- D Normal pattern; a day 4-to-7 drop of 10% is sufficient for continued monitoring
Correct answer: B. The response is inadequate; a second dose of methotrexate should be given on day 7
Explanation
Single-dose methotrexate protocol requires at least a 15% decline in serum hCG from day 4 to day 7 to indicate adequate response. A decline of <15% (here only 10%) from day 4 to day 7 indicates inadequate response and warrants a second methotrexate dose. A 5% change from day 1 to day 4 is expected (hCG often transiently rises in days 1–4 due to continued trophoblastic activity before the drug takes effect). Surgical intervention is reserved for rupture, hemodynamic instability, or failure after two doses.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.