Objectives 1. To investigate the efficacy of 800 μg misoprostol (a PGE1 analogue) when administered to women pretreated with mifepristone for early pregnancy termination. 2. To establish means of minimising gastrointestinal side effects by comparing two different misoprostol regimens. The impact of these regimens on blood pressure was investigated in a subgroup of patients.

Design A randomised study of 150 women of 56 days gestation, or less, allocated to receive oral misoprostol either in a single dose of 800 μg or as two doses of 400 μg administered sequentially 2 h apart; in each case misoprostol was administered 36 to 48 h after receiving mifepristone 200 mg orally.

Main outcomes Complete abortion rates, the frequency and severity (patients' perception) of gastrointestinal side effects, and blood pressure changes in response to prostaglandin administration.

Results The overall success rate was 93%. Seventy-one (95%) women who received a single dose of misoprostol and sixty-nine (92%) who received the sequential dose aborted completely. There were two ongoing pregnancies in the first group (2.5%) and three (4%) in the second. The overall ongoing pregnancy rate was 3%. The incidence of diarrhoea was significantly lower for women receiving the sequential dose, and no significant differences were found in the incidence of the other gastrointestinal side effects. The only noted significant change in blood pressure was in diastolic pressure 4 h after the administration of the higher dose of prostaglandin, but this was slight.

Conclusions The combination of mifepristone and oral misoprostol provides an alternative method to inducing abortion of pregnancies of up to eight weeks gestation. Patients receiving the single dose of 800 μg were more troubled by diarrhoea than those on the sequential regimen. The ongoing pregnancy rate was higher than previously reported with vaginal or parenteral administration of prostaglandin.