• Evaluation of the Drug Rating Questionnaire-Subject (DRQS), and the Addiction Research Center Inventory (ARCI) [ Time Frame: Days 1, 3, 5, 7, and 9 ] [ Designated as safety issue: Yes ]
• Evaluation of the DRQS, the ARCI, the Street Value Assessment Questionnaire (SVAQ), and the Treatment Enjoyment Assessment Questionnaire (TEAQ) [ Time Frame: Day 1, 3, 5, 7, 8, 9, and 10 ] [ Designated as safety issue: Yes ]

The purpose of this study is: (1) to assess the effect of oxycodone HCl on niacin-induced dysphoric effects when oxycodone HCl is administered in combination with niacin in subjects with a history of opioid abuse; (2) to assess the abuse liability of 4 times the usual recommended dose of Acurox (oxycodone HCl 40 mg plus niacin 240 mg) versus oxycodone HCL 40 mg alone in subjects with a history of opioid abuse.

• Drug: Niacin
• Drug: Oxycodone HCL plus Niacin
• Drug: Placebo
• Drug: Oxycodone HCl

Inclusion Criteria:

• Subject is male or female between 18 and 55 years of age
• Subject meets DSM-IV Criteria for the Diagnosis of Opioid Substance Abuse and subject is unlikely to experience an idiosyncratic reaction or respiratory depression after ingesting 40 mg of oxycodone
• Body weight is not more than 20% above or below ideal body weight
• Subject agrees to abstain from any Rx or OTC drugs (except as authorized by the Investigator) or alcohol
• Subject is in generally good health
• Subject is reliable, willing, cooperative, able to communicate effectively, and has a minimum of a 6th grade reading level
• Subject has an acceptable score on the MMSE for cognitive impairment
• For women of child-bearing potential: woman is not pregnant and not nursing, and is practicing an acceptable method of birth control

Exclusion Criteria:

• Subject has a disease that may endanger the subject or the validity of the data
• Subject is currently physically dependent on opiates or alcohol
• Subject was exposed to any investigational drug within 30 days prior to the inpatient phase
• Subject has a history of hypersensitivity to any drug, or a known allergy to any component of the study drug formulation
• Subject has a positive urine drug screen for a non-opiate drug
• Subject has a predisposing condition that may place the subject at risk for receiving niacin or oxycodone, or confound the study analyses
• Subject ingested niacin at doses higher than SDI within 14 days prior to the inpatient phase
• Subject has an abnormal bleeding tendency