Skin rash, urticaria, pruritus; somnolence & prolonged sedation, alertness decreased, confusional state, euphoric mood, hallucinations, fatigue, headache, dizziness, ataxia, post-op sedation & anterograde amnesia, paradoxical reactions eg, agitation, involuntary movements (including tonic/clonic seizures & muscle tremor), hyperactivity, hostility, rage reaction, aggressiveness, paroxysmal excitement & assault in childn & elderly; seizures; may enhance physical dependence, w/drawal symptoms; nausea, vomiting, constipation, hiccup & dry mouth; severe cardiorespiratory adverse events; resp depression, apnea, resp arrest or cardiac arrest, hypotension, heart rate disorder, vasodilator effects, dyspnea & glottis spasm; skin reactions, CV reactions, bronchospasm, anaphylactic shock; erythema & pain on inj site, thrombophlebitis & thrombosis.