Pilot Study of the Efficacy and Safety of Q8003 in Patients Who Have Undergone Total Knee Arthroplasty or Total Hip Arthroplasty

This Phase 2 study is a 3 arm, open-label pilot study to evaluate: * the analgesic efficacy of a flexible ascending regimen of Q8003 compared to a low dose regimen of Q8003 (3 mg/2 mg and potentially up to 6 mg/ 4mg) and to 1-2 Percocet® 5 mg/325 mg tablets. Study drug will be administered every 4-6 hours over a 48-hour Treatment Period to inpatients with moderate to severe postoperative pain who have undergone primary unilateral total knee arthroplasty or total hip arthroplasty. * for the flexible ascending regimen of Q8003 treatment group, to evaluate the adequacy of the algorithm for conversion of IV PCA morphine to oral morphine equivalent doses of Q8003. * the safety of the flexible ascending regimen of Q8003 administered over a 48-hour Treatment Period.