Objective: To compare the complete abortion rate, the induction-to-abortion time, and side effects between 600 mcg and 800 mcg misoprostol sublingually.

Materials and Methods: Total, of 108 pregnant women with gestational age less than 12 weeks with early pregnancy loss from March 2020 to February 2021 at the Department of Obstetrics and Gynecology, Queen Savang Vadhana Memorial Hospital, were included. For group 1 (n=54), 600 mcg misoprostol was administrated sublingually. For group 2 (n=54), 800 mcg misoprostol was administrated sublingually. If the abortion did not occur, the repeated misoprostol in the same dose would be administrated sublingually every 6 hours for a maximum of three doses.

Results: There was no significant difference in the complete abortion rate between the two groups (55.6% in the 600 mcg misoprostol group, 64.7% in the 800 mcg misoprostol group, p=0.339, and 95% CI 0.082 to 1.862). The induction-to-abortion time was 9.5 hours (IQR 6.75 to 48.00) in the 600 mcg misoprostol group and 10 hours (IQR 6.00 to 60.00) in the 800 mcg misoprostol group. The side effects of both groups were similar, included abdominal pain, diarrhea, nausea and vomiting, fever, heavy bleeding, and headache.

Conclusion: The efficacy of the 600 mcg misoprostol was noninferior to 800 mcg misoprostol. The adverse effects were similar in both groups. Mean induction-to-abortion time was also similar in both groups.