Reduced hydrolytic lability of epoprostenol in the presence of cationic micelles.

The rapid hydrolysis of epoprostenol to 6-keto-prostaglandin F1 alpha is hydronium ion-catalyzed even at pH 10 or higher. In the presence of 1.0% hexadecyltrimethylammonium chloride, the rate was reduced significantly (1580-fold at pH 2 and 283-fold at a physiological pH). This decrease in the hydrolysis rate is attributed to two causes: favorable partitioning of epoprostenol in the micellar phase and electrostatic repulsion between the hydronium ion and the cationic micellar surface.