Cw. Lin et Tm. Cham, EFFECT OF PARTICLE-SIZE ON THE AVAILABLE SURFACE-AREA OF NIFEDIPINE FROM NIFEDIPINE-POLYETHYLENE GLYCOL-6000 SOLID DISPERSIONS, International journal of pharmaceutics, 127(2), 1996, pp. 261-272
Solid dispersions containing 5%, 10%, 20%, 30% and 50% of nifedipine w
ere prepared with polyethylene glycol (PEG) 6000 as carrier, respectiv
ely, by the fusion method. Drug release from four different size fract
ions of nifedipine-polyethylene glycol 6000 solid dispersions were exa
mined. The probability parameters of Weibull distribution or log-norma
l distribution could be obtained from linear regression of the dissolu
tion data. The effects of particle size on the dissolution rate of nif
edipine were evaluated in terms of the time course of the available su
rface area (S(t)). The X-ray diffraction patterns showed that nifedipi
ne was dispersed homogeneously in an amorphous state in the solid disp
ersions with nifedipine concentration up to 10%. The initial values an
d faster rate of decrease of S(t) during the dissolution process were
markedly enhanced in the solid dispersions with lower contents of nife
dipine (5% and 10%) due to the formation of high energy metastable (am
orphous) states of the drug and differences in the particle sizes had
little effect on the values of the available surface area and the diss
olution of the drug. Values of available surface area were particle si
ze dependent for the solid dispersions with higher contents of nifedip
ine (20%, 30% and 50%) and the rate of decrease of S(t) was enhanced a
s the particle size reduced.