Serum human chorionic gonadotropin clearance curves in patients with interstitial pregnancy treated with systemic methotrexate.

Objective: To evaluate short-term effectiveness of systemic methotrexate (MTX) in interstitial pregnancy.

Design: Case series.

Setting: Two Dutch teaching hospitals.

Patient(s): Eight consecutive patients with an unruptured interstitial pregnancy.

Intervention(s): Four doses of 1.0 mg/kg IM MTX alternated with 0.1 mg/kg oral folinic acid. Serum hCG concentrations were determined before the first MTX injection and followed until levels were undetectable. A second MTX course was started on day 14, if by then serum hCG concentrations were > 40% of the initial value. Serum hCG clearance curves of all patients in the present study were compared with those from our earlier studies, in which a different folinic acid regimen (15 mg orally) was used.

Main Outcome Measure(s): Serum hCG clearance curves.

Result(s): All patients were treated successfully: five with one course and three with two courses. Serum hCG clearance curves of these patients tended to decline more rapidly than those successfully treated with the 15 mg folinic acid regimen.

Conclusion(s): Systemic MTX is an attractive therapeutic option in the conservative treatment of unruptured interstitial pregnancy. The regimen of four doses of 1.0 mg/kg IM MTX alternated with 0.1 mg/kg folinic acid is effective. Serum hCG clearance curves may serve as a guideline for monitoring MTX treatment, thus enabling a timely detection of impending treatment failure.