Antitussive drugs delivered by ion exchange resins

The present invention relates generally to a mixture of coated and non-coated sulfonic acid cation exchange resins (Amberlite IR69) cross-linked with about 8% divinyl benzene onto which dextromethorphan has been loaded. About 30% of the drug/resin complexes are coated with a mixture of ethyl cellulose or ethyl cellulose latexes with plasticizers and water dispersible polymers such as SURELEASE. The coating level is about 50% w/w drug. Coated and uncoated drug/resin complexes are loaded with drug to about 45% by weight drug/resin complex. The ratio of coated and uncoated drug/resin complexes is about 55/45. The particle sizes of the coated and uncoated drug/resin complexes is about 20 to about 300 and about 20 to about 250 microns, respectively.