GSK618334 is being developed as an innovative treatment for substance dependence and potentially other compulsive behavioral disorders. This study will evaluate the safety, tolerability and pharmacokinetics of single doses of GSK618334 in healthy volunteers.

Inclusion Criteria:

• Healthy adult male subject, aged between 18 and 50 years of age 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, psychiatric or laboratory evaluation, including 12-lead ECG and 24 hour Holter ECG. A subject with a clinical abnormality or laboratory parameter(s) outside the reference range for this age group may be included only if the Investigator considers the finding will not introduce additional risk factors and will not interfere with the study procedures.
• Signed and dated written informed consent prior to participation in the study.
• The subject is able to understand and comply with protocol requirements, instructions and protocol-stated restrictions.

Exclusion Criteria:

• The subject has a positive pre-study urine drug screen including alcohol at the screening visit and/or prior to receiving the first dose of study medication. Drugs that will be screened for are amphetamines, barbiturates, cocaine, opiates, cannabinoids, methadone, benzodiazepines, phencyclidine (PCP) and cotinine. If any of these tests are positive the investigator may re-test the subject and the subject may be included if the re-test is negative.
• A positive pre-study Hepatitis B surface antigen, Hepatitis C antibody, or HIV 1/2 result at the screening visit.
• Abuse of alcohol defined as an average weekly intake of greater than 28 units or an average daily intake of greater than 4 units.
• The subject has clinically significant elevations in liver function tests (LFT) that are elevated above the reference range at pre-study screening and remain elevated with a repeat LFT, and/or prior to receiving the first dose of study medication.
• Consumption of grapefruit juice or grapefruit within 7 days prior to receiving the first dose of study medication.
• Any subject who is not prepared to eat the standard meals provided by the Clinical Pharmacology Research Unit (CPRU) during the study.
• Participation in a clinical trial with a new chemical entity within 4 months before the first dose of study medication or marketed compound within 3 months before receiving the first dose of study medication.
• Use of prescription or non-prescription drugs, including, over the counter remedies, 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 receiving the first dose of study medication, unless in the opinion of the Investigator and sponsor the medication will not interfere with the study procedures or compromise subject safety.
• Loss of more than 600mL blood during the 120 days before study start.
• History or presence of allergy to the study drug or drugs of this class, or a history of other allergy that, in the opinion of the physician responsible, contraindicates his participation in the study.
• History of regular use of tobacco- or nicotine-containing products within 6 months of the start of the study (i.e., from Screening Visit 1).
• An unwillingness of the male subject to use condoms or practise abstinence to prevent exposure of a female partner to semen from the start of the study (i.e., from Screening Visit 1) until 90 days after the study treatment has ended.
• History of psychiatric disorder either Axis I or II by DSM-IV.
• History or presence of respiratory illnesses, gastrointestinal, hepatic or renal disease or other condition known to interfere with the absorption, distribution, metabolism or excretion of drugs.
• The subject has a screening ECG with values outside of ranges defined in the protocol.
• The subject has a screening heart rate <50 or >100 bpm and a systolic blood pressure >140 and <100 mmHg and a diastolic blood pressure >90 and <60 mmHg in the semi-supine position.
• The subject has a reduction in systolic blood pressure of 20 mmHg or more, or a reduction in diastolic blood pressure of 10 mmHg or more on standing compared to the supine measurement at screening.
• History of long QT syndrome (personal or family) or other cardiac conduction disorder, or other clinically significant cardiac disease.
• The subject is unable to abstain from strenuous physical activity for 24 h prior to the screening visit and for 24 h prior to admission for each treatment period.
• Inability of the subject to be successfully trained in tests of cognition prior to receiving the first dose of study medication.