Tablets for the controlled release of an active ingredient in a zero-order or near zero-order fashion are provided. The tablet includes a core and a coating. The core includes at least one active pharmaceutical agent and a polyethylene oxide with a molecular weight of between about 1,000,000 and 10,000,000, preferably between about 4,000,000 and 8,000,000. The core material is optionally, but preferably, coated with a cellulosic material. The active pharmaceutical agent can be hydrophilic, hydrophobic, or amphiphilic. When the active pharmaceutical agent is a hydrophilic agent, it is preferred that the coating is a relatively hydrophobic cellulose, such as ethylcellulose or propylcellulose. However, if the tablet is uncoated, it can provide a near-zero-order release rate rather than a zero-order release rate. When the active pharmaceutical agent is a hydrophobic or amphiphilic agent, the hydrophilic polymeric carrier is the same as in the first embodiment, the coating is a relatively more hydrophilic cellulose. The release rate for the active pharmaceutical agent can be controlled by adjusting the thickness of the coating, and, optionally, by adjusting the concentration of the polymeric excipients, as well as certain non-polymeric excipients which may optionally be present. An advantage of using relatively high molecular weight polyethylene oxide is that the release is pH independent, unlike where ionic polymers such as polyacrylic acids are used. Further, active pharmaceutical agents including functional groups that might react with such polymers can be used without an adverse reaction between the active agent and the polymer.
