Inclusion Criteria:  All subjects (young and elderly):  A signed and dated informed consent form before any study-specific screening procedure was performed; Healthy male and female subjects as determined by the Investigator on the basis of medical history, physical examination, clinical laboratory test results, vital signs and digital 12-lead electrocardiogram (ECG); Non-smoker or ex-smokers for at least 3 months at screening; BMI between 18 and 30 kg/m2, inclusive; Negative tests for hepatitis B surface antigen (HBsAg), anti-hepatitis C virus antibodies (HCV Ab) and anti-human immunodeficiency virus antibodies (HIV-1 and HIV-2 Ab) at screening; Clinical laboratory test results clinically acceptable at screening and admission to the study;  Negative screen for alcohol and drugs of abuse at screening and admission to the study;  If male:  Using an effective method of contraception with a pregnant partner or partner of childbearing potential (condom or occlusive cap [diaphragm or cervical or vault caps] with spermicidal foam or gel or film or cream or suppository; true abstinence; or vasectomy) throughout the study;  Refraining from donating sperm throughout the study.  Young subjects only:  Males and females aged between 18 and 40 years, inclusive.  If female:  No childbearing potential by reason of surgery or at least 1 year post-menopause (i.e., 12 months post last menstrual period), or menopause confirmed by follicle-stimulating hormone (FSH) testing; If of childbearing potential, using an effective non-hormonal method of contraception [intrauterine device or intrauterine system; condom or occlusive cap (diaphragm or cervical or vault caps) with spermicidal foam or gel or film or cream or suppository; true abstinence; or vasectomized male partner, provided that he is the sole partner of that subject] for all the duration of the study;  If of childbearing potential, negative serum pregnancy test at screening and negative urine pregnancy test on admission to the study.  Elderly subjects only:  Males and females older than 65 years, inclusive.  Exclusion Criteria:  All subjects (young and elderly):  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; Clinically relevant surgical history; History of relevant atopy or drug hypersensitivity; History of alcoholism or drug abuse; Consumption of more than 14 units of alcohol a week [1 unit corresponds to 1 glass of 12° wine (10 cL), 1 glass of 45° pastis (2.5 cL), 1 glass of 40° whisky (2.5 cL), 1 glass of 12° champagne (10 cL), 1 glass of 18°aperitif drink (7 cL) or one 25-cL glass of 5°beer]; Significant infection or known inflammatory process at screening or admission to study; Acute gastrointestinal symptoms (e.g., nausea, vomiting, diarrhoea, heartburn) at the time of screening or admission to the study; Previous use of BIA 5-1058; Use of any investigational drug or participation in any clinical trial within 90 days prior to screening; Participation in more than 2 clinical trials within the 12 months prior to screening; Donation or reception of any blood or blood products within the 3 months prior to screening; Vegetarians, vegans or other medical dietary restrictions; Not able to communicate reliably with the Investigator;  Unlikely to co-operate with the requirements of the study.  If male:  Not using an accepted effective method of contraception;  Refusing to refrain from donating sperm throughout the study.  Young subjects only:  Use of medicines within 2 weeks of admission that could affect the safety or other study assessments, in the Investigator's opinion;  If female of childbearing potential:  Pregnant or breastfeeding;  Not using an accepted effective contraceptive method or using oral contraceptives.  Elderly subjects only:  For elderly subjects, previously prescribed medications that interfered with absorption, distribution, metabolism, and excretion or safety/tolerability evaluation of BIA 5-1058 and adrenal or renal function were prohibited; however, previously prescribed medications that did not interfere with absorption, distribution, metabolism, and excretion or safety/tolerability evaluation of BIA 5-1058, adrenal or renal function and which could not interfere with the objectives of the study were allowed if the dose regimen had been stable for at least 4 weeks and was expected to remain stable throughout the study. Such concomitant medications were to be reviewed and mutually agreed upon by the Sponsor and the Investigator.