Effect of core size and excipients on the lag time and drug release from a pulsatile drug delivery system.

BACKGROUND: Pulsatile drug delivery system, based on a core-in-cup dry-coated tablet was examined and evaluated. The system consisted of three different parts: a core tablet (with increasing diameter), containing the active ingredient acting as reservoir; an impermeable outer shell; and a top cover layer barrier. The core tablet contained either caffeine or theophylline as model drugs.

OBJECTIVE: To investigate and evaluate how the geometrical characteristics of the core tablets, drugs, and excipients influence the behavior of the system presented, namely, lag time and drug release.

RESULTS AND DISCUSSION: Drug release exhibited a lag time period dependent on the core tablet size, drug solubility, and characteristics of polymer and polymer mixtures. The lag time was increased by increasing the core tablet diameter and the quantity of soluble lactose in the top cover layer.

CONCLUSIONS: The quantity and characteristics of materials, the core tablet size, and the erosion of the top cover layer were found to be important factors in controlling the lag time and release. Increase in core tablet diameter resulted in lower lag times and greater release and release rates. Similarly, by increasing sufficiently the quantity of the soluble excipient lactose, in the top layer we observed a decrease of the lag times and an increase of release.