The present invention includes an expandable osmotic layer and a coating suspension for providing an expandable osmotic layer, both of which are useful for the manufacture of controlled release dosage forms. The expandable osmotic layer of the present invention may be produced using the coating suspension of the present invention. Advantageously, the coating suspension of the present invention can be used to coat expandable osmotic layers under both wet and dry process conditions without sacrificing the quality of the expandable osmotic layers produced, and therefore provides a relatively robust coating suspension that facilitates commercial production of controlled release dosage forms including a coated expandable osmotic layer.