• Sum of Pain Intensity Differences Relative to the Baseline Pain Intensity. [ Time Frame: Baseline value to 48 hours after first study drug intake. ] [ Designated as safety issue: No ]
  Pain Intensity assessed at predefined time points over a 48 hour period using an 11-point Numeric Rating Scale (NRS) where a score of zero indicates "no pain" and a score of ten indicates "pain as bad as you can imagine". Differences calculated as [baseline-post baseline] at each predefined time point. The theoretical maximum range of Sum of pain intensity differences (SPID48) is from -480 (indicative of an increase in pain) to 480 (indicative of a decrease in pain).
  
  

• Number of Participants Using Rescue Medication [ Time Frame: Baseline up to 72 hours after first study drug intake ] [ Designated as safety issue: No ]
  Number of participants who used at least one dose of rescue medication during the 72 hour double blind period.
  
  
• Total Pain Relief (TOTPAR) [ Time Frame: Baseline to 48 hours after first study drug intake ] [ Designated as safety issue: No ]
  Total pain relief (TOTPAR) in the 48 hour period from the first dose of study drug. The subject was to indicate pain relief at rest in response to the following question: How much relief have you had from your starting pain? None = 0, A little = 1, Some = 2, A lot = 3 and Complete = 4. The theoretical maximum range of Total pain relief (TOTPAR)48 is from 0 (indicative of no pain relief) to 192. The higher the value the better the pain relief.
  
  
• Sum of Pain Intensity Differences Over 6 Hours (SPID6) Relative to the Baseline Pain Intensity [ Time Frame: Baseline to 6 hours after intake of first study drug ] [ Designated as safety issue: No ]
  Pain Intensity assessed at predefined time points over a 6 hour period using an 11-point Numeric Rating Scale (NRS) where a score of zero indicates "no pain" and a score of ten indicates "pain as bad as you can imagine". Differences calculated as [baseline-post baseline] at each predefined time point. The theoretical maximum range of Sum of pain intensity differences (SPID6) is from -60 (indicative of an increase in pain) to 60 (indicative of a decrease in pain).
  
  
• Sum of Pain Intensity Differences Over 12 Hours (SPID12) Relative to the Baseline Pain Intensity [ Time Frame: Baseline to 12 hours after first study drug intake ] [ Designated as safety issue: No ]
  Pain Intensity assessed at predefined time points over a 12 hour period using an 11-point Numeric Rating Scale (NRS) where a score of zero indicates "no pain" and a score of ten indicates "pain as bad as you can imagine". Differences calculated as [baseline-post baseline] at each predefined time point. The theoretical maximum range of Sum of pain intensity differences (SPID12) is from -120 (indicative of an increase in pain) to 120 (indicative of a decrease in pain).
  
  
• Sum of Pain Intensity Differences Over 24 Hours (SPID24) Relative to the Baseline Pain Intensity [ Time Frame: Baseline to 24 hours after first study drug intake ] [ Designated as safety issue: No ]
  Pain Intensity assessed at predefined time points over a 24 hour period using an 11-point Numeric Rating Scale (NRS) where a score of zero indicates "no pain" and a score of ten indicates "pain as bad as you can imagine". Differences calculated as [baseline-post baseline] at each predefined time point. The theoretical maximum range of Sum of pain intensity differences (SPID24) is from -240 (indicative of an increase in pain) to 240 (indicative of a decrease in pain).
  
  
• Sum of Pain Intensity Differences Over 72 Hours (SPID72) Relative to the Baseline Pain Intensity [ Time Frame: Baseline to 72 hours after first intake of study drug ] [ Designated as safety issue: No ]
  Pain Intensity assessed at predefined time points over a 72 hour period using an 11-point Numeric Rating Scale (NRS) where a score of zero indicates "no pain" and a score of ten indicates "pain as bad as you can imagine". Differences calculated as [baseline-post baseline] at each predefined time point. The theoretical maximum range of Sum of pain intensity differences (SPID72) is from -720 (indicative of an increase in pain) to 720 (indicative of a decrease in pain).
  
  

Subjects undergoing bunionectomy often experience moderate to severe acute pain post-surgery. Normally such pain is controlled when subjects receive repeated doses of opioid analgesics. However, opioid therapy is commonly associated with side effects such as nausea, vomiting, sedation, constipation, addiction, tolerance, and respiratory depression. CG5503, a newly synthesized drug with an immediate release (IR) formulation, also acts as a centrally acting pain reliever but has a dual mode of action. The aim of this trial is to investigate the effectiveness (level of pain control) and safety (side effects) of CG5503 IR 75mg compared with no drug (placebo) or one dose of morphine (an opioid commonly used to treat post-surgical pain). This trial is a randomized, double-blind (neither investigator nor patient will know which treatment was received), active- and placebo-controlled, parallel-group, multicenter trial to evaluate the treatment of acute pain after bunionectomy. The trial will include a blinded 72 hour inpatient phase immediately following bunionectomy, during which subjects will be treated with either 75-mg CG5503 IR, a placebo, or 30-mg morphine, and pain relief will be periodically assessed. Assessments of pain relief include the pain intensity numeric rating scale (PI), pain relief numeric rating scale (PAR), and patient global impression of change scale (PGIC). Safety evaluations include monitoring of adverse events, physical examinations, and clinical laboratory tests. Venous blood samples will be collected for the determination of serum concentrations of CG5503 and morphine. The alternative trial hypothesis is that at least 1 dose strength of CG5503 will be different from placebo in controlling pain at 48 hours.