Effect of nitroglycerin-soluble additives on the stability of molded nitroglycerin tablets.

Nitroglycerin vapor pressures at 25 degrees C were determined for additive-nitroglycerin systems over the additive-nitroglycerin weight ratio range of 0.5 to 3.0 for 16 additives exhibiting solubility in nitroglycerin. The effects of the additives on nitroglycerin chemical stability at 25 degrees C and 50 degrees C were also studied. Tablet stability characteristics, i.e., content uniformity, open-dish stability, and chemical decomposition were evaluated for selected tablet formulations. Most additives lowered the vapor pressure of nitroglycerin sufficiently to stabilize content uniformity when used at additive-nitroglycerin weight ratios near 1. Higher additive levels are needed for significant potency stabilization in open-dish stability tests, but these levels normally decrease the chemical stability of nitroglycerin. However, stabilization of content uniformity, a twofold reduction of potency loss in an open-dish stability test, and chemical stability are possible with at least three of the additives studied.