Solid state studies of drug-cyclodextrin inclusion complexes in PEG 6000 prepared by a new method

The melting method was investigated as a possible method for producing drug -cyclodextrin (CD) inclusion compounds in a carrier. Various solid dispersi ons of alpha-, beta- and gamma-CD in polyethylene glycol (PEG) 6000 with an d without the addition of 5% w/w indomethacin or griseofulvin were prepared using the original components. Characterisations of the samples included X -ray powder diffraction, modulated-temperature differential scanning calori metry and dissolution tests by the paddle method according to USP XXI stand ard. Evidence of a complex between indomethacin and beta-CD in PEG 6000 was found. An indomethacin-gamma-CD complex formed a well defined phase in the PEG carrier, with tetragonal structure and unit cell parameters a = 23.885 (35) Angstrom and c = 23.181(64) Angstrom. No complexation of indomethacin with alpha-CD, or with griseofulvin and beta-CD could be detected. It is su ggested that competition between PEG and the drug for the binding to differ ent CDs along with varying patterns of water loss from the CDs influence th e inclusion reaction. The formation of complexes was accompanied by a decre ase in the relative crystallinity of the dispersions. Dissolution tests sho wed that the CDs have a delaying effect on the release of indomethacin from PEG 6000 in the order alpha-CD<gamma-CD less than or equal to beta-CD. (C) 1999 Elsevier Science B.V. All rights reserved.