The stability of prostaglandin E1 in dilute physiological solutions at 37 degrees C

The stability of prostaglandin E1 (PGE1) in three physiologic solutions was studied at body temperature (37 degrees C) over 32 days. The solutions were 100 mcg/ml PGE1 in isotonic saline (pH 4.5), 0.1 M phosphate buffered water (pH 7.4) or 0.01 M phosphate buffered isotonic saline (pH 4.7). PGE1 was found to be more stable in the saline and buffered saline solutions at the pH values of 4.5 and 4.7 respectively. Twenty-five per cent of the PGE1 remained at 32 days in these solutions while 95% of the PGE1 in the solution at pH 7.4 was degraded by day 14. The degradation of PGE1 in the acidic solutions appeared to be nearly linear when plotted on a semilog graph. This data allows one to use PGE1 in an aqueous, slightly acidic solution in a system that requires it to be kept at 37 degrees C for up to 30 days such as a biologically implantable pump. Investigators can use such a system in vivo to study the effect of known concentrations of PGE1 given over a period of time to a specific area of interest.