Wet resinate beads consisting of carboxylic ion exchange resin and codeine have been coated with polyureas by use of interfacial water promoted polyreaction of various diisocyanates. Retardation of drug release from coated resinates was estimated based on the measurement of codeine concentration during elution in simulated gastric juice. It has been found that the rate of codeine release depends on the parameters of encapsulation process: type of diisocyanate used, content of water in resinate, duration of swelling of resinate with water, diisocyanate/resinate weight ratio, reaction time and temperature.