Development and validation of a stability-indicating method, structural elucidation of new degradation products from misoprostol by LC-MS time-of-flight, and an ex vivo study of vaginal permeation

Misoprostol (MSP) is commonly prescribed in obstetrics and gynecology clinical practice for labor induction, cervical ripening, first-trimester pregnancy termination, and the treatment of postpartum hemorrhage. Furthermore, there is a lack of comprehensive discussion evaluating how different commercially available formulations influence the overall efficacy of MSP, even though reports indicate issues with the quality of these formulations, particularly regarding stability and vaginal absorption processes. This study investigates the stability of MSP under acidic conditions and its in vitro permeation using swine vaginal mucosa. A forced degradation study was conducted using 0.2 M HCl, and a high-efficiency LC method was developed. Three degradation products were identified and characterized using electrospray ionization-high-resolution quadrupole-time-of-flight-MS, with respective m/z values of 391.2508, 405.2705, and 387.2259, respectively. These results suggest that the degradation mechanism involves dehydration of the beta-hydroxy ketone moiety, followed by isomerization to its most resonance-stable form and de-esterification. Finally, the in vitro permeation study revealed that the esterified form of MSP was unable to permeate the mucosa and required prior degradation for any component to be detected in the receptor fluid.