May precipitate w/drawal symptoms in patients physically dependent on opioids. Hypothyroidism, adrenocortical insufficiency, asthma or decreased resp reserve, prostatic hyperplasia, hypotension, shock, inflammatory or obstructive bowel disorders or myasthenia gravis. Avoid abrupt w/drawal. May precipitate w/drawal symptoms in physically dependent patients who have recently used pure agonists eg, morphine. Development of psychological & physical dependence (repeated use). May affect ability to drive or operate machinery. Renal or hepatic impairment. Pregnancy. Infants especially neonates. Elderly or debilitated patients.