Abstract: Described is a stable pharmaceutical composition of 3-(hydroxymethyl-5,5-diphenylhydantoin disodium phosphate ester, the prodrug of 5,5-diphenylhydantoin (phenytoin) a commonly used drug for the treatment and management of epilepsy and other types of convulsive states. It has been found that degradation of the prodrug to phenytoin can be controlled by controlling the pH of the composition. Controlling the pH to between 8.3 to 9.4 results in the production of diphenylglycinamide as the primary degradant and minimization of degradation to phenytoin. If the pH is maintained at a lower or higher value, then the degradation pattern changes, with earlier than expected product failure.

Abstract: An injectable, aqueous pharmaceutical composition for the treatment of cardiac conditions comprising an effective amount of methyl 3-[4-(2-hydroxy-3-isopropylamino)propoxy]phenylpropionate hydrochloride (esmolol) for treating such a cardiac condition, said composition comprising about 1 mg to 250 mg of esmolol per milliliter of said injectable pharmaceutical composition; 0.01 to 0.02M buffer; said composition having a pH range of 4.5 to 5.5, the esmolol degrading in aqueous solution to produce 3-[4-(3-propionic acid)phenoxy]-1-isopropylamino-2-propanol hydrochloride, said 3-[4-(3-propionic acid)-phenoxyl]-1-isopropylamino-2-propanol hydrochloride having a pK in the pH range of said composition to thereby act as a secondary buffer to increase the buffer capacity and minimize the change in pH as degradation occurs, whereby the stability of esmolol in an aqueous composition is enhanced.