Poly(d,l-lactide) microspheres with progesterone loadings of 0, 10, 20, 30 and 50% w/w were manufactured using an interrupted
solvent evaporation process. Spherical microspheres with loadings close to the theoretical values were produced. The glass
transition of the polymer could be identified by a step change in the heat capacity measured by TMDSC. Progesterone was found
to plasticise the glass transition temperature at contents of 20% w/w or less. At a 30% loading, cold crystallisation of progesterone
was seen indicating that an amorphous form of the drug was present; these microspheres were found to exhibit a pitted surface.
TMDSC of the 50% progesterone samples suggested that most of the drug was present as crystals. This was supported by the SEM
and PXRD results.