In vitro controlled release of theophylline from metal-drug complexes

Two new metal-drug complexes constructed from non-toxic zinc and theophylline (TPL), an anti-asthmatic active drug, have been introduced into a release system based on matrices of hydroxypropylmethylcellulose (HPMC) and microcrystalline cellulose (MC). The release rate of TPL from the metal-drug complexes could be controlled by the amount of MC added, and the release mechanism changed from anomalous transport to Fickian diffusion.