Programmable drug release of highly water-soluble pentoxifylline from dry-coated wax matrix tablets

The programmable release of pentoxifylline from a dry-coated wax matrix tablet containing behenic acid as wax matrix was investigated at 37 degrees C in Japanese Pharmacopeia XII 1st (pH 1.2) and 2nd (pH 6.8) fluids. The dry-coated tablet consisted of a low drug concentration (33% w/w) in the outer layer tablet and a high concentration (50-67% w/w) in the core. The drug release from the wax matrix significantly increased after penetrating the core; therefore, the drug release profiles showed specific biphasic curves. Because the contact angle of the wax matrix tablet increased with a decrease in the drug concentration, the fluid penetration in wax matrix tablet increased with an increase of the drug concentration. The time required for 75% drug release (T75) decreased with an increasing drug concentration in the core, and the T75 at pH 6.8 was slightly longer than that in pH 1.2. The larger core tablet had a shorter T75, indicating that the drug release rate was controlled by regulating the drug concentration and/or the weight of the core tablet.