Medical abortion with methotrexate 75 mg intramuscularly and vaginal misoprostol

Methotrexate (50 mg/m² intramuscularly and 50 mg orally) followed by vaginal misoprostol have proven to be > 90% effective at causing abortion in women at less than 49 days' gestation. Although the effectiveness of the oral dose (which has a lower serum bioavailability) demonstrates that a methotrexate dose of 50 mg/m² may be more than necessary, an intramuscular regimen is more advantageous because it is less costly. This trial was designed to investigate the potential effectiveness of a single dose of methotrexate, 75 mg intramuscularly, in a regimen for early abortion. One hundred subjects received 75 mg methotrexate intramuscularly followed 5 to 6 days later by 800 μg misoprostol vaginally. The misoprostol dose was repeated if the abortion did not occur. Outcome measures included successful abortion (complete abortion without requiring a surgical procedure), duration of vaginal bleeding, and side effects. One subject was lost to follow-up. Complete abortion occurred in 94 of 99 (94.9%, 95% CI 90.6, 99.3%) patients. The complete abortion rate was no different for earlier gestations: 38 of 40 (95.0%, 95% CI 88.2, 100%) at up to 42 days' gestation and 56 of 59 (94.9%, 95% CI 89.3, 100%) at more than 42 days' gestation (p = 0.99). Abortion occurred in the 24 h following the initial or repeat misoprostol dose (immediate success) in 70.7%; the remaining 24.2% of women who aborted did so after a delay of 22 ± 10 days (mean + standard deviation). Vaginal bleeding lasted 17 ± 8 days and 11 ± 7 days in immediate success and delayed success patients, respectively. Overall, 77.8%, 86.9%, and 91.9% of patients had passed the pregnancy by 14, 28, and 35 days, respectively, after receiving methotrexate. This preliminary evaluation demonstrates that a medical abortion regimen using 75 mg methotrexate intramuscularly appears to have similar effectiveness to one with 50 mg/m² methotrexate.