The morphine hydrogel suppository (MHS), a monolithic sustained release rectal preparation, has been developed and evaluated in three pilot studies. Two release profiles have been prepared. The first, MHS(B), has a high initial release rate followed by a constant release for the remainder of a 12-h period. The second, MHS(S), has the same constant release rate for 12 h. MHS(B) is intended to attain and maintain analgesic or near analgesic plasma concentrations of morphine, and MHS(S) to maintain that concentration for successive 12-h periods. The pilot studies suggest that MHS may be of value in the management of postoperative pain.