The dissolution of nortriptyline HCl from polyethylene glycol solid dispersions

Abstract

The dissolution characteristics of nortriptyline hydrochloride dispersions in a range of different molecular weight polyethylene glycol carriers have been investigated. The release rate was found to be higher from dispersions in PEG 3400 than from the drug alone, while a logarithmic decrease was seen with increasing carrier molecular weight. Studies indicated that there was little difference in release rate from flash- and slow-cooled dispersions. A linear relationship was found between drug dissolution rate and concentration in PEG 20 000 up to 25% w/w drug. The release rate was shown to increase with rotation speed, although the results obtained were not consistent with the relationship proposed by Levich (Levich, V.G., Physicochemical Hydrodynamics, Prentice Hall, NJ, 1962, pp. 60–72). A hypothesis has been presented for the involvement of solubilisation of the drug at the solid-liquid interface as a mechanism for the observed dissolution behaviour.