Experimental Medicine Study to Validate Pharmacodynamic Pain Assessments in Healthy Volunteers With an Opioid Analgesic (Remifentanil)

Inclusion Criteria: * Non-smoking, healthy adult male, aged 20-45 years inclusive. * Body weight \>50 Kg and BMI within the range 18.5-29.9 Kg/m2 inclusive * Healthy as judged by a responsible physician. No clinically significant abnormality identified on the medical or laboratory evaluation. A subject with a clinically significant abnormality or laboratory parameters outside the reference range for the relevant age group may be included only if the Investigator and Medical Monitor consider that the finding will not introduce additional risk factors and will not interfere with the study procedures. * A normal 12-lead ECG recording at the pre-study medical. * Signed and dated written and informed consent must be obtained for all subjects prior to admission to the study. * The subject is able to understand and comply with the protocol requirements, instructions and protocol-stated restrictions. Exclusion Criteria: * The subject has a positive pre-study urine screen for drugs of abuse or positive alcohol test. * Abuse of alcohol defined as an average weekly intake of greater than 21 units or an average daily intake of greater than 3 units. 1 unit is equivalent to a half-pint (220 mL) of beer or 1 (25 mL) measure of spirits or 1 glass (125 mL) of wine. * Use of prescription drugs as well as vitamins, herbal and dietary supplements (including St John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to the first dose of study medication, unless it is the opinion of the Investigator and Medical Monitor that the medication will not interfere with the study procedures or compromise subject safety. * History or presence of allergy to the study drug or drugs of this class, or a history of drug or other allergy that, in the opinion of the physician responsible, contraindicates their participation. * Has a systolic blood pressure which is outside the range of 90 to 140 mmHg, diastolic blood pressure is outside the range of 50 to 90 mmHg or heart rate is outside the range 40 to 90 bpm. * Has a QTcB \>450 msec. * Has a significant medical history of dizziness, blackouts, fainting or vaso-vagal attacks. * Has received over-the-counter (OTC) medicine within 48h before the first dosing day. Subjects who have taken OTC medication may still be entered into the study, if, in the opinion of the Principal/Co-Investigator, the medication received will not interfere with the study procedures or compromise safety. * Has a history or presence of gastro-intestinal, hepatic or renal disease or other condition known to interfere with the distribution, metabolism or excretion of drugs. * The subject has received an investigational drug or participated in any other research trial within 84 days for new chemical entities and marketed drugs or 5 half-lives, or twice the duration of the biological effect of any drug (whichever is longer) prior to the first dose of current study medication.