STUDIES ON DRUG-RELEASE FROM A CARBOMER TABLET MATRIX

The purpose of this investigation was to study the drug release mechan isms for tablet matrices of carbomer. Carbomer is a polymer of acrylic acid which is cross-linked with polyalkenyl polyether. The drug and t he carbomer were blended and directly compressed into tablets using a laboratory Carver press. The influence of the level of carbomer, the t ype of drug, and the pH of dissolution media were investigated by meas uring drug release kinetics. In general, the release of a relatively n eutral molecule (e.g. theophylline) in the pH 7.2 phosphate buffer sol ution appears to exhibit nearly zero-order kinetics via a diffusion-co ntrolled mechanism for all polymer levels studied (10-85%). The drug r elease process based on diffusion can be described by the general expr ession: M(t) = k(1)t(1/2) + k(2)t, where M(t) represents the amount of the drug released at time t, and k(1), k(2) are related to kinetic co nstants characteristic of the drug delivery systems. The release kinet ics are modified when an ionic species, such as sodium salicylate, is incorporated into the tablet matrix.