A Safety, Efficacy and Tolerability Trial of Pregabalin as Add-On Treatment in Pediatric and Adult Subjects With Primary Generalized Tonic-Clonic (i.e., Grand Mal) Seizures.

Inclusion Criteria:

- Seizures classified as Primary Generalized Tonic Clonic Seizures

- Must have at least 1 PGTC seizure in the 8 weeks prior to screening

- Must have a minimum of 3 PGTC seizures during the 8-week baseline phase and at least 1
PGTC in each 4-week period of the baseline phase

- Currently receiving adequate and stable dosage of 1 to 3 anti-epileptic treatments
(stable within 28 days of screening)

- Signed informed consent and assent if a minor

- Ability to comply with daily seizure and dosing diary requirements and all study
procedures

Exclusion Criteria:

- A current diagnosis of febrile seizures, or seizures related to an ongoing acute
medical illness

- Focal seizures (simple partial, complex partial, or partial becoming secondarily
generalized)

- Status Epilepticus within 1 year prior to screening

- Lennox-Gastaut syndrome, infantile spasms, Benign Epilepsy with Centrotemporal Spikes
(BECTS) and Dravet syndrome

- Seizures related to drugs, alcohol, or acute medical illness

- Any change in anti-epileptic treatment regimen (type of medication or dose; VNS
alteration) within 28 days of the screening visit or during the baseline phase

- Progressive or potentially progressive structural CNS lesion or a progressive
encephalopathy.

- Progressive inborn errors of metabolism.