Inclusion Criteria:

• Subjects (male or female) must be > 18 years or ≤ 80 years of age, with a diagnosis of epilepsy with partial seizures, as defined in the International League Against Epilepsy (ILAE) classification of seizures; partial seizures may be simple or complex, with or without secondary tonic-clonic generalization.
• Subjects must be have been diagnosed with epilepsy for at least 2 years, and must have been unresponsive to treatment with at least two but no more than five prior antiepileptic drugs (AEDs), and at the time of study enrollment are on stable dosages of 1 or 2 standard AEDs.
• They must have had a 12 lead electrocardiogram (ECG) without clinically significant abnormal findings prior to randomization.
• Subjects must have had magnetic resonance imaging or contrast enhance computed tomography scan of the brain that demonstrated no progressive structural central nervous system abnormality at the time of the diagnosis of epilepsy.
• Women of childbearing potential must be established on an effective method of contraception during the study. Women should also have a negative pregnancy test prior to study entry.
• During the 6-week baseline period, subjects must have had a minimum of four partial seizures, with no 28 day period free of partial seizures with or without secondary generalization. A caregiver or witness must be with the subject for a sufficient duration to accurately chronicle the occurrence of seizures. These seizures must have been documented in the subject's diary.
• Subjects with electroencephalograph (EEG) testing done within 2 years of randomization. EEG abnormalities should be consistent with a diagnosis of focal-onset epilepsy.
• Signed and dated informed consent will be obtained from each subject (only include those able to consent) in accordance with the local regulatory and legal requirements.
• Subjects who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other trial procedures. Subjects who are willing, but need assistance for self administered questionnaires may be considered acceptable, but must first be discussed on a case-by-case basis with the Pfizer monitor prior to any to any screening tests or procedures for the study.

Exclusion Criteria:

• Females who are pregnant, breastfeeding, or intending to become pregnant during the course of the trial.
• Subjects with other neurologic illness that could impair endpoint assessment, or patients with Lennox-Gastaut syndrome, absence seizures, status epilepticus within the 12 months prior to study entry, or with seizures due to an underlying medical illness or metabolic syndrome.
• Subjects with clinically significant liver disease or with a calculated creatinine clearance of <60mL/min.
• Subjects with a history of lack of response, hypersensitivity or poor tolerability to gabapentin or pregabalin.
• Previous use of gabapentin or pregabalin within 2 weeks prior to screening or likelihood of engaging in these treatments during the study period.
• Use of prohibited medications as listed in the protocol in the absence of appropriate washout phase or the likelihood of requiring treatment during the study period with drugs not permitted by the study protocol.
• Participation in any other studies involving investigational or marketed products, concomitantly or within 30 days prior to entry in the study.
• Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with trial participation or investigational product administration or may interfere with the interpretation of trial results and, in the judgment of the investigator, would make the subject inappropriate for entry into this trial.
• Subjects who are not suitable to be treated with pregabalin or gabapentin according to the respective local labeling.
• Subjects with a history of retinal abnormalities or treatment with retinotoxic agents.