Pulsed proton NMR and solid-liquid fat ratio determinations in suppository vehicles and aminophylline suppositories

The physical state, melting behaviour and release rate of aminophylline suppositories were studied during storage. The fraction of non-crystallized fat, assessed by pulse NMR, varies between different vehicles. At room temperature several vehicles do not seem to be completely crystalline. Aging, as observed in prolonged melting time and a reduced release rate, is not expressed in a drastic reduction of the fraction of non-crystallized fat, as observed by NMR. On the contrary the mobility of the protons in the non-crystallized state is likely to offer a more promising tool to monitor aging.