This was a randomized (patients are assigned different treatments based on chance), open-label, three-way crossover study, performed in normal, healthy adults. Each patient received orally administered treatments (a different treatment during each dosing phase): Treatment A: single dose of Dilaudid SR 16 mg administered under fasting conditions without the naltrexone block;Treatment B: single dose of Dilaudid SR 16 mg administered under fed conditions without the naltrexone block, Treatment C: single dose of Dilaudid SR 16 mg administered under fasting conditions with naltrexone HCL 50mg block (3 oral doses of 50mg each administered 12 hours prior to , at the time of, and 12 hours after Dilaudid SR 16mg administration). There was a 7-day washout period between dosing phases.