Study to Assess the Bioavailability, Pharmacokinetics, Safety, and Tolerability of AVP-923 in Healthy Adult Participants

Inclusion Criteria: * Healthy adults, 18 to 65 years of age, inclusive * Willing to sign informed consent form * Cytochrome P450 2D6 genotype that confers extensive metabolizer profile (as per documented phenotype interpretation from local laboratory and approval from Avanir) Exclusion Criteria: * History or presence of significant pulmonary, hepatic, renal, hematologic, allergic, endocrine (including diabetes), immunologic, dermatologic, neurologic (including history or presence of seizures or convulsive disorders), psychiatric disease (including history of suicidal ideation or behavior) or any eating disorder deemed clinically significant by the investigator * History or presence of significant cardiovascular disease, including complete heart block, QT interval corrected for heart rate (QTc) prolongation, and/or torsades de pointes * History or presence of any gastrointestinal (GI) disease or condition that could compromise participant safety or affect the absorption of study drug, including GI ulcers, GI bleeding, esophageal or gastric varices, and dyspepsia requiring regular (i.e., more frequently than once a month) use of acid-reducing drugs * Known hypersensitivity/intolerance to dextromethorphan or quinidine * Participants whom the principal investigator or his delegate deems to be ineligible