Abstract: Method for printing on a pharmaceutical tablet by etching a printing plate to form a pattern of etchings therein within an area corresponding to an outline of the tablet, varying the ink-retaining volumes of the etchings in a pre-determined manner and in a direction across the etching pattern from one side to an opposite side, placing ink into the etchings, and transferring ink from the etchings in the etched printing plate onto an outer surface of the tablet. Variations in the ink-retaining volumes of the etchings cause a larger amount of ink to be transferred from etchings having a larger ink-retaining volume than from etchings having a smaller ink-retaining volume during the ink transfer stage. This causes different changes in the color of the outer surface of the tablet dependent on the amount of ink being transferred.

Abstract: A controlled release pharmaceutical formulation which undergoes substantially or approaches zero order release of active drug is provided, preferably in the form of a coated tablet, containing a core portion from which medicament, such as procainamide hydrochloride, is slowly released over a controlled length of time. The core also includes one or more primary hydrocolloid gelling agents which is a hydropropylmethyl cellulose having a viscosity of within the range of from about 1,000 to about 6,000 centipoises in 2% solution at 20.degree. C., and a methoxyl content of 28-30%, optionally a secondary hydrocarbon gelling agent, such as hydroxypropyl cellulose and/or methyl cellulose, one or more non-swellable binders and/or wax binders (where the medicament and/or hydrocolloid gelling agents are non-compressible), one or more inert fillers or excipients, one or more lubricants, and optionally one or more anti-adherents such as silicon dioxide and water.