The two synthetic prostaglandin analogues, carboprost and misoprostol, are used extensively in obstetric and gynaecological practice. Our recent research of these compounds' use for intra-umbilical injection to treat adherent placenta necessitated their storage in solution for 3-4 days. This raised concerns over the stability and applied dosage in the in-house infusion preparations. It requires various pharmacological preparations before administration in clinical practice. We used LCMS to develop a simultaneous, valid, fast and simple method to assess the stability and recovery of their in-house preparations in different conditions. The linearity between 0-40 microg/ml was above 0.995. The reproducibility (CV) was within 5.2%. The limit of quantitation of the method for both compounds is about 2 microg/ml. The accuracy of both compounds from 0.4-40 microg/ml is 96.4-104.3% while the precision is 0.4-7.4%. The recoveries of carboprost in the infusion were from 100.3+/-4.0 to 102.4+/-1.6% and that of misoprostol in Cytotec tablet was from 44.9+/-3.5 to 50.0+/-5.0% in water and saline at 4 degrees C and room temperature. No interference was found from the matrix and between the tested compounds. The compounds were basically stable for 6 days in water and in saline, whether they were stored at 4 degrees C or at room temperature. However, only half of the dosage of misoprostol was recovered in the solution. Therefore, misoprostol dosage should be adjusted before clinical application.