Hypersensitivity. Acute resp depression, cor pulmonale, cardiac arrhythmias, severe bronchial asthma, chronic obstructive airways disease, paralytic ileus, suspected surgical abdomen, delayed gastric emptying, acute alcoholism, brain tumor, increased cerebrospinal or ICP, head injury, severe CNS depression, convulsive disorders, delirium tremens, hypercarbia, concurrent administration of MAOIs or w/in 2 wk of discontinuation of use. Not recommended for pre-op use or for the 1st 24 hr post-op. Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption. Moderate to severe hepatic impairment. Severe renal impairment (CrCl <10 mL/min).