Pharmacokinetics of different routes of administration of misoprostol

BACKGROUND: The pharmacokinetic parameters of four different routes of administration of a single dose of 400 μg of misoprostol were studied. METHODS: A total of 40 women undergoing termination of pregnancy by suction evacuation was randomized by computer model to receive 400 μg of misoprostol by one of four routes: (i) sublingual (ii) oral (iii) vaginal and (iv) vaginal with addition of water. Venous blood samples were taken at 0, 1, 2, 5, 10, 20, 30, 45, 60, 120, 240 and 360 min after the administration of misoprostol. Misoprostol acid (MPA) was determined in serum samples using gas chromatography/tandem mass spectrometry. RESULTS: Sublingual misoprostol achieved the highest serum peak concentration (Cmax) (574.8 ± 250.7 pg/ml) of MPA and this was significantly higher than those in the other groups [Oral: 287.6 ± 144.3 pg/ml (P < 0.01), vaginal: 125.2 ± 53.8 pg/ml (P < 0.001) and vaginal with water: 162.8 ± 57.1 pg/ml (P < 0.001)]. The time to peak concentration (Tmax) was similar in both the sublingual (26.0 ± 11.5 min) and oral groups (27.5 ± 14.8 min) and was significantly shorter than those in both vaginal groups. The area under the MPA concentration versus time curve up to 360 min in the sublingual group (743.7 ± 291.2 pg˙h/ml) was significantly greater than those in oral (402.8 ± 151.6 pg˙h/ml, P < 0.05) and vaginal (433.7 ± 182.6 pg˙h/ml, P < 0.05) groups, but no significant difference was found between sublingual and vaginal administration if water (649.3 ± 333.8 pg˙h/ml) was added. CONCLUSION: The new sublingual route of administration of misoprostol demonstrated a great potential to be developed into a method of medical abortion.