Stability of hydralazine hydrochloride in aqueous vehicles

The stability of hydralazine hydrochloride in aqueous vehicles which contain either dextrose, fructose, lactose, maltose, mannitol, sorbitol or sucrose has been studied using a stability-indicating high-performance liquid chromatographic method. Dextrose, fructose, lactose and maltose had adverse effects on the stability of hydralazine. In mannitol (better than sorbitol) and sorbitol, hydralazine was stable for about 21 days (loss in potency of less than 10%) and sucrose had an adverse effect only after its hydrolysis to fructose and dextrose. The optimum pH range of stability in dextrose was approximately between 3.2 and 4.4. The first-order rate of decomposition increased with an increase in the concentration of dextrose but not with an increase in the concentration of hydralazine. In the absence of other excipients the phosphate and citrate buffers did not adversely affect the stability of hydralazine hydrochloride.