Effect of polyamidoamine (PAMAM) dendrimers on the in vitro release of water-insoluble nifedipine from aqueous gels.

The objective of this study was to determine the effect of ethylenediamine core PAMAM dendrimers on the release of nifedipine suspended in aqueous gels and to correlate release to the increase in solubility afforded by the dendrimers. Drug release from aqueous 5% HPMC gels containing nifedipine (2% wt/vol) through 0.2-microm membranes was measured using Enhancer cells and 50% ethanolic solution as the receptor medium. The release from gels containing PAMAM G-3 and G-5 (0.25%-1% wt/vol) was compared with gels containing the cosolvent isopropyl alcohol (10%-80% vol/vol). PAMAM dendrimers significantly increased the solubility of nifedipine. This caused a significant increase in the release rate of nifedipine from the gel suspensions. The increase in drug release depended on the concentration and generation size of the dendrimers added. For higher generations (G-5) lower concentrations were needed to obtain equivalent increases in release. Although the increase in solubility and release was not as high as from gels containing high concentrations of the cosolvent isopropyl alcohol, the dendrimers prevented the recrystallization of the drug that was observed when the gels containing isopropyl alcohol were left open.