Single-centre, open-label, randomised, two-way cross-over study consisting of 2 periods separated by a washout period of 14 days or more.

Single-centre, open-label, randomised, two-way cross-over study consisting of 2 periods separated by a washout period of 14 days or more. In one period, subjects received three single-doses of 1 g paracetamol separated by 6 hours and 1.5 hours after the last paracetamol dose a single-dose of 50 mg OPC was administered.In the other period, a single-dose of 50 mg OPC was administered alone.

Inclusion Criteria:

• Subjects who are able and willing to give written informed consent.
• Male or female subjects aged between 18 and 45 years, inclusive.
• Subjects of body mass index (BMI) between 19.0 and 30.0 kg/m2, inclusive.
• Subjects who are healthy as determined by pre-study medical history, physical examination, vital signs, complete neurological examination and 12-lead ECG.
• Subjects who have negative tests for HBsAg, anti-HCVAb and HIV-1 and HIV-2 Ab at screening.
• Subjects who have clinical laboratory test results clinically acceptable at screening and admission to each treatment period.
• Subjects who have a negative screen for alcohol and drugs of abuse at screening and admission to each treatment period.
• Subjects who are non-smokers or ex-smokers for at least 3 months.
• (If female) She is not of childbearing potential by reason of surgery or, if of childbearing potential, she uses 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 female) She has a negative serum pregnancy test at screening and a negative urine pregnancy test on Day -1 of each treatment period.

Exclusion Criteria:

• Subjects who have 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.
• Subjects who have a clinically relevant surgical history.
• Subjects who have any clinically relevant abnormality in the coagulation tests.
• Subjects who have any clinically relevant abnormality in the liver function tests (a case-by-case decision for any abnormality must be discussed with the Sponsor before inclusion).
• Subjects who have a history of relevant atopy or drug hypersensitivity, particularly to paracetamol or any COMT inhibitor.
• Subjects who have a history of alcoholism or drug abuse.
• Subjects who consume more than 14 units of alcohol a week.
• Subjects who have a significant infection or known inflammatory process at screening or admission to each treatment period.
• Subjects who have acute gastrointestinal symptoms (e.g., nausea, vomiting, diarrhoea, heartburn) at the time of screening or admission to each treatment period.
• Subjects who have received paracetamol within 2 weeks of admission to the first period.
• Subjects who have used any other medicines within 2 weeks of admission to first period that may affect the safety or other study assessments, in the investigator's opinion.
• Subjects who have previously received OPC.
• Subjects who have used any investigational drug or participated in any clinical trial within 90 days prior to screening.
• Subjects who have participated in more than 2 clinical trials within the 12 months prior to screening.
• Subjects who have donated or received any blood or blood products within the 3 months prior to screening.
• Subjects who are vegetarians, vegans or have medical dietary restrictions.
• Subjects who cannot communicate reliably with the investigator.
• Subjects who are unlikely to co-operate with the requirements of the study.
• Subjects who are unwilling or unable to give written informed consent.
• (If female) She is pregnant or breast-feeding.
• (If female) She is of childbearing potential and she does not use an approved effective contraceptive method or she uses oral contraceptives.