Amorphous formulations of APIs in polymers tend to absorb water from the atmosphere. This absorption of water can induce API recrystallization, leading to reduced long-term stability during
storage. In this work, the phase behavior of different formulations was investigated as a function of relative humidity. Indomethacin and naproxen were chosen as model APIs and poly(vinyl
pyrrolidone) (PVP) and poly(vinyl pyrrolidone-co-vinyl acetate) (PVPVA64) as excipients.