Bioavailability Study of BIA 5-453

Inclusion Criteria: * aged between 18 and 45 years, inclusive. * had a body mass index (BMI) between 19 and 30 kg/m2, inclusive. * were healthy as determined by pre-study medical history, physical examination, vital signs, complete neurological examination and 12-lead ECG. * had negative tests for HBsAg, anti-HCVAb and HIV-1 and HIV-2 Ab at screening * had clinical laboratory test results clinically acceptable at screening and admission to the first treatment period. * had negative screen for alcohol and drugs of abuse at screening and admission to the first treatment period. * were non-smokers or smoked ≤ 10 cigarettes or equivalent per day. * was able and willing to give written informed consent. Exclusion Criteria: * had a clinically relevant history or presence of respiratory, gastrointestinal, renal, hepatic, haematological, lymphatic, neurological, cardiovascular, psychiatric, musculoskeletal, genitourinary, immunological, dermatological, endocrine, connective tissue diseases or disorders. * had a clinically relevant surgical history. * had a clinically relevant family history. * had a history of relevant atopy or drug hypersensitivity. * had a history of alcoholism or drug abuse. * consumed more than 14 units of alcohol a week. * had a significant infection or known inflammatory process at screening or admission to the first treatment period. * had acute gastrointestinal symptoms (e.g., nausea, vomiting, diarrhoea, heartburn) at the time of screening or admission to the first treatment period. * used medicines within 2 weeks of admission to first period that affected the safety or other study assessments, in the investigator's opinion. * used any investigational drug or participated in any clinical trial within 3 months prior to screening. * participated in more than 2 clinical trials within the 12 months prior to screening. * donated or received any blood or blood products within the 3 months prior to screening. * was a vegetarian, vegan or with medical dietary restrictions. * could not communicate reliably with the investigator. * was unlikely to co-operate with the requirements of the study. * was unwilling or unable to give written informed consent.