M. Alden et al., EFFECT OF COUNTERIONS ON THE INTERACTIONS IN SOLID DISPERSIONS BETWEEN POLYETHYLENE-GLYCOL, GRISEOFULVIN AND ALKALI DODECYL SULFATES, International journal of pharmaceutics, 110(3), 1994, pp. 267-276
Solid dispersions of polyethylene glycol (PEG) 3000 and 10% w/w griseo
fulvin with or without different surfactants incorporated were prepare
d by the melting method. The anionic surfactants lithium dodecyl sulph
ate (LiDS), sodium dodecyl sulphate (SDS) and potassium dodecyl sulpha
te (KDS) were added in equivalent amounts, similar to 2% w/w. Phase an
alysis was performed by X-ray powder diffraction and investigation of
short-range structure by C-13-CP/MAS solid-state NMR. In all samples w
ith surfactant added, solid solutions (PEG/MDS)(1-x) griseofulvin(x) w
ere formed. The properties of the solid solutions with Na+ and K+ ions
were almost identical. The addition of LiDS created a structure of th
e solid solution that was more crystalline than that structure of the
sodium- and potassium-containing compounds. The ion with the highest c
harge-to-radius ratio, Li+, formed chemical bonds that were different
from those of the other ions. This was indicated by a changed influenc
e on the hydrophilic parts of the griseofulvin molecules in the lithiu
m compound. The melting behaviour of the solid solutions, investigated
by DSC, showed a second transformation in the melt at 186-196 degrees
C, indicating a two-phase region in the liquid phase. For the lithium
-containing compounds the transformation appeared at lower temperature
than for the sodium- and potassium-containing compounds.