Article ID Journal Published Year Pages File Type
8513555 Journal of Pharmaceutical Sciences 2018 39 Pages PDF
Abstract
Phase transformations of poorly water-soluble drugs, in low concentration, supersaturated aqueous solutions are of considerable interest. Herein, fluorescence lifetime and steady-state fluorescence spectroscopy were employed to investigate the fluorescence properties of the autofluorescent compound, felodipine (a 1,4-dihydropyridine calcium channel blocker), when present as free drug in solution, drug-rich aggregates, and crystals. Measurements were also performed in the absence and presence of liver microsomes. To study nonfluorescent drugs, an environment-sensitive fluoroprobe, 6-propionyl-2-dimethylaminonaphthalene, was employed. The lifetime of free felodipine in solution in simple media was found to be ∼0.4 ns, whereas felodipine present in drug-rich aggregates and crystals was characterized by a longer lifetime of ∼2 and ∼9 ns, respectively. In the presence of structures containing lipids, the local environment of felodipine was found to change based on fluorescence characteristics and the concentration where felodipine aggregates formed was greatly increased. The lifetime of 6-propionyl-2-dimethylaminonaphthalene in solutions containing clotrimazole (an imidazole derivative with antimycotic activity) or efavirenz (a non-nucleoside reverse transcriptase inhibitor with antiviral activity) increased on aggregate formation as a result of the change in polarity of the probe local environment. Fluorescence lifetime coupled with steady-state fluorescence spectroscopy was demonstrated to be effective in identifying the concentration where drug aggregates formed, contributing to improved understanding of the phase behavior of poorly water-soluble drugs in biologically relevant media.
Related Topics
Health Sciences Pharmacology, Toxicology and Pharmaceutical Science Drug Discovery
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