Diffusion of drugs from hydrogels and liposomes as drug carriers

BACKGROUND: The mass transfer of model drugs Lidocaine hydrochloride and Dihydroquercetin from hydrogels (the usual carriers for topical drugs), and hydrogels containing liposomes, as novel drug vehicles, was studied. Diffusion experiments were performed using a Franz diffusion cell. Experimental data were used to calculate drug diffusion coefficients across membranes, and their effective diffusion coefficients from hydrogels and liposome containing hydrogels. For the first time the diffusion resistance of all drug carriers was determined from corresponding diffusion coefficients. The main aim of this work was the study of drug diffusion coefficients from liposomes and their comparison with related diffusion coefficients from hydrogels to find how liposomes contribute to prolonged and controlled drug release. RESULTS: Drug diffusion coefficients were: 1.38 . 10(-8)-m(2) s(-1) for Lidocaine hydrochloride and 5.96 . 10(-9)m(-2) s(-1) for Dihydroquercetin, while corresponding effective diffusion coefficients from hydrogels were: 7.82 . 10(-10)m(2) s(-1) and 7.98 . 10(-10)m(2) s(-1), respectively. Effective diffusion coefficients from liposome-containing hydrogels were:4.82 . 10(-10)m(2) s(-1) (Lidocaine hydrochloride) and 4.305 . 10(-10)m(2) s(-1) (Dihydroquercetin). Diffusion resistances for the two hydrogels were almost the same. Very similar values of diffusion resistances for all liposome dispersions were obtained. CONCLUSION: Calculated diffusion coefficients and resistances demonstrate that liposomes, as drug carriers, significantly affect diffusion rates. The results obtained could be used whenever diffusion-controlled drug release is required. (C) 2010 Society of Chemical Industry