Perforated coated tablets for controlled release of drugs at a constant rate

Tablets with a central hole and a water-impermeable coating were prepared. These perforated coated tablets (PCTs) dissolve and release drug through the central hole only. In vitro release of the model drugs sodium benzoate and benzamide from PCTs occurred at a constant rate up to 80% release. The zero-order release rate varies with hole size, drug solubility, drug concentration, diluent solubility, and binder concentration. These results demonstrate that the PCT design can be used to prepare drug delivery devices which release at controllable constant rates.