Stability of procaine hydrochloride in a buffered cardioplegia formulation.

The stability of procaine hydrochloride in a buffered cardioplegia solution was studied. The formulation of Ringer's injection with added increments of potassium and magnesium plus procaine hydrochloride was buffered to a pH of 7.3-7.6 with tromethamine. Procaine hydrochloride content was measured in triplicate by ultraviolet spectrophotometry at set time intervals and at temperatures of 22, 40, and 61 degrees C. The time required for procaine to degrade to the lower shelf-life limit of 90% of its initial concentration was extrapolated to be approximately two days at room temperature and 11 days under refrigeration. It is recommended that the basic buffered cardioplegia solvent be manufactured separately, and the procaine hydrochloride be added at the time of dispensing to minimize its loss of potency.