The study is designed to evaluate the safety and efficacy of oxycodone/naltrexone (a) and oxycodone/naltrexone (b) versus placebo. During the blinded phase of the study (inpatient portion) the dosing regimen is 1 capsule containing Oxycodone Hydrochloride plus Naltrexone Hydrochloride (a) or Oxycodone plus Naltrexone Hydrochloride (b) or placebo taken with 4 to 6 ounces (oz) of water every 6 hours (q6h) for 48 hours following the first dose (Multiple-dose Period) while in-house. Then for the open-label phase of the study (outpatient portion) dosing will occur every 4 to 6 hours prn with Oxycodone plus naltrexone. The active and placebo study medications will appear identical. Study subjects with acute postoperative pain of moderate to severe intensity following unilateral bunionectomy surgery will be randomized after surgery, and will stay at the study center for the duration of the 48-hour double-blind period after dose 1 of study medication. The study will be conducted in the following 4 periods: 1) a pre-treatment period, 2) a multiple-dose inpatient period (double-blind), 3) a multiple-dose outpatient period (open-label), and 4) End of Study/Follow-up.