The thermal and photostability of solid pharmaceuticals

Abstract

Drugs degrade to different extents on separate exposure to heat, moisture, oxidation and light. Combination of these stresses causes very complex behaviour. Many studies have been reported of the thermal behaviour of drugs in the solid-state, but most of the information available on the photodegradation of drugs refers to reactions in solution, (usually aqueous) and photoreactions in the solid-state are even more complex. In drug formulations, the presence of excipients adds further complications because the excipients may increase, have no effect on, or decrease the inherent stabilities of the drug. The literature has been explored to review the thermal and photostabilities of solid pharmaceuticals.