Compressed Donut-Shaped Tablets with Zero-Order Release Kinetics

AbstractPurpose. Simple uncoated compressed tablets with a central hole (donut-shape) are proposed to provide a constant drug release over a long period of time (>20 hrs). The effect of hole size and drug solubility on the release kinetics is investigated. Methods. The donut-shaped polyethylene oxide (PEO, Mw = 4 × l06) tablets (600 mg and 12 mm diameter) are bored with a drill bit (3/32″, 7/64″, 1/8″, and 5/32″). Results. The release of theophylline from the donut-shaped tablets is zero order (80 – 90% release) before rapidly decreasing. As the hole size is increased from 7/64″ to 5/32″, the release rate increases and the release time is shortened. However, the release of theophylline from the donut-shaped tablet with a hole size of 3/32″ follows the same anomalous release profile from a tablet without a hole. As drug solubility increases, the duration of linear drug release is shortened to 65 – 70% release followed by a severe tailing at the later stage of the release. Conclusions. Donut-shaped PEO tablets with a hole provide zero-order release kinetics because the effect of the releasing surface area on the release kinetics is reduced.