Egg albumin microspheres containing sulphamethizole.

Egg albumin microspheres containing sulphamethizole have been prepared by a capillary extrusion procedure. The microspheres were coarse (dvn = 1835 microns) with a narrow size distribution and tended to lose their spherical shape on drying. Scanning electron microscopy revealed that the microspheres were porous with drug concentrated at the periphery of the matrix. This excess surface concentration resulted in a burst effect for drug release in acidic dissolution media with up to 30 per cent drug released in 2 min. This was followed by a more gradual release of drug and finally the release tended to tail off as the matrix became depleted of drug. The average t50 per cent release was 12 min. Variable swelling of the matrix occurred during the first 20-30 min of dissolution which complicated the interpretation of release data. Treatment of the albumin spheres with spermaceti or paraffin wax tended to reduce swelling and increased the t50 per cent release to 33 min and 43 min respectively. Cross-linking of the matrix with aldehydes or by gamma-irradiation proved unsatisfactory.