Physical stability of semisynthetic suppository bases.

Changes in the melting range of several semisynthetic suppository bases were studied over time. X-ray diffraction studies characterized the changes as amorphous to crystalline transitions, with likely polymorphic effects occurring concurrently. Use of a modified Krowczynski apparatus to test pure base and single-ingredient suppositories showed dramatic hardening of the materials over periods as short as 6 weeks. Data were obtained by differential scanning calorimetry on freshly solidified, incrementally aged, and equilibrated samples. These methods may be used as both predictive and ongoing physical stability tests in the evaluation of suppository bases and formulas.