The invention relates to a pharmaceutical preparation for controlled, sustained release of dextromethorphan comprising a polystyrene sulfonate resin which has been cross- linked with about 3% to about 10% divinyl benzene, having an average particle size of at least 40 µm and less than 100 pm onto which dextromethorphan has been loaded in a ratio expressed in weight amounts of dextromethorphan-hydrobromide to resin of about 1:6 to about 1:10 and at least one pharmaceutically acceptable adjuvant.