A Comparative Bioavailability/Food Effect Study of Immediate-Release and Extended-Release Tramadol HCl/Acetaminophen Combination Products Following Single-Dose and Multiple-Dose Administration in Healthy Adult Volunteers

Inclusion Criteria: * Adult males or females aged 18-55 years inclusive with body mass index (BMI) between 18-30 kg/m2 * Healthy as determined by pre-study medical history, physical examination and 12-lead ECG * Clinical laboratory tests within the reference ranges or clinically acceptable to the Investigator * Negative for hepatitis B surface antigen (HBsAg), hepatitis C antibody and human immunodeficiency virus (HIV) I and II tests at screening * Negative for drugs of abuse and alcohol at screening and admission * Non-smokers for at least 3 months preceding screening * If female, were not currently pregnant or breast feeding and were using medically acceptable methods of contraception and if male, were themselves and their female partners using medically acceptable methods of contraception * Able and willing to give written informed consent. Exclusion Criteria: * Subjects who did not conform to the above inclusion criteria * Female subjects who were pregnant, trying to become pregnant, lactating or not using acceptable methods of contraception * Clinically relevant history or presence of respiratory, gastrointestinal, renal, hepatic, haematological, lymphatic, neurological, cardiovascular, psychiatric, musculoskeletal, genitourinary, immunological, dermatological, connective tissue diseases or disorders * Clinically relevant surgical history * Clinically relevant family history * History of relevant atopy * History of relevant drug hypersensitivity * History of alcoholism * History of drug abuse * Male subjects who consumed more than 21 units of alcohol a week and female subjects who consumed more than 14 units of alcohol a week * Significant infection or known inflammatory process on screening * Acute gastrointestinal symptoms at the time of screening and/or admission (e.g. nausea, vomiting, diarrhoea, heartburn) * Acute infection such as influenza at the time of screening or admission * Use of prescription drugs within 7 days of first dosing, unless agreed as non clinically relevant by the Principal Investigator and Sponsor * Use of over-the-counter medication excluding routine vitamins but including mega dose vitamin therapy within 14 days of first dosing, unless agreed as non clinically relevant by the Principal Investigator and Sponsor * Use of any investigational drug or participation in any clinical trial within 3 months of their first dosing * Donation or receipt of any blood or blood products within the previous 3 months prior to first dosing * Vegetarians, vegans or having medical or cultural dietary restrictions. * Inability to communicate reliably with the Investigator. * Subjects who were unlikely to co-operate with the requirements of the study