PREDICTION OF DRUG-RELEASE BY CHARACTERIZATION OF THE TORTUOSITY IN POROUS CELLULOSE BEADS USING A SPIN-ECHO NMR TECHNIQUE

The tortuosity of pores in cellulose beads has been estimated using a spin echo NMR technique and by direct release measurements. The tortuo sity determined with NMR was slightly higher (tau = 2.7) than the valu es obtained from direct release measurements (tau = 1.6-2.4:). The dev iations are explained in terms of unfulfilled prerequisites for the mo dels describing the dissolution process. Another explanation may be di fferences in drug loading and pore structure in the outer and inner la yer of the porous cellulose beads. The NMR measurements are described in derail and special problems occurring when applying this technique are discussed. In this work it is shown to be possible to predict drug release from structural data of porous cellulose beads.