Inclusion criteria:

• Newly-diagnosed with absence epilepsy and never been treated with Anti-epileptic drugs (AEDs).
• Diagnosis demonstrated on one of two 5-minute hyperventilation tests.
• Investigator must judge that the subject and parent/guardian are likely to comply with all study procedures.
• Parent/guardian must given written informed consent. Subjects who are intellectually able to understand the concepts and procedures of the protocol must give assent by also signing the consent or by signing a separate assent form.
• Results of all screen assessments are judged to be clinically acceptable to the investigator and do not indicate any reasons why entry into the study would be contraindicated.

Exclusion criteria:

• Seizures are the result of a currently active, known, and identifiable intracerebral lesion.
• Has partial or generalized tonic-clonic seizures.
• Has a progressive neurological disorder defined as being unstable for at least 12 weeks prior to the Screen Phase.
• Has a psychiatric disorder requiring medication, or has had a past psychiatric condition that was both judged to be severe and required hospitalization.
• Has any clinically significant chronic cardiac, renal, or hepatic medical condition.
• Has a condition that affects the absorption, distribution, metabolism, or excretion of drugs.
• Is currently taking any psychoactive drugs to treat hyperactivity disorder or attention deficit disorder.
• Has taken any investigational drug within 12 weeks prior to the Screen Phase.
• Is sexually active.
• Is either pregnant (i.e., confirmed by pregnancy test at Screen) or breastfeeding.
• Has a clinically significant chronic medical disorder which the investigator and/or GSK medical monitor determine warrants exclusion.