An Open Label Study to Evaluate the Effects of Ezogabine/Retigabine Added to Existing Anti-epileptic Drug(s) on Urinary Voiding Function in Subjects With Partial Onset Seizures

This is a multicentre, open label study to examine the effect of ezogabine/retigabine on the voiding function of adult subjects with drug-resistant partial onset seizures (POS). Subjects fulfilling the study entry criteria at Screening and at Baseline including a comprehensive eye examination by an ophthalmologist or retina specialist and a skin assessment by the investigator will receive ezogabine/retigabine. The starting dose of ezogabine/retigabine will be 300 mg/day. Subjects will be up titrated by 150 mg/day weekly up to the maximum ezogabine/retigabine daily dose of 1200 mg (or the highest tolerated dose). During the 49 days of the treatment phase, subjects will undergo three repeat non-invasive assessments of voiding function. In addition, subjects who meet pre-determined criteria for voiding dysfunction will undergo multichannel cystometry in order to characterise bladder hypocontractility, bladder outlet obstruction or a combination of events which clinically is manifest with difficulty emptying the bladder or acute urinary retention. At the end of the Treatment Phase, all subjects will enter the Taper Phase, a 3-week down titration period. Subjects who have new findings of abnormal pigmentation of the retina, unexplained vision loss, pigmentation of non-retinal ocular tissue or discoloration of skin, lip, nail, or mucosa since baseline will be asked to enter the Safety Follow-Up / Continuation Phase. All subjects will undergo 6-monthly comprehensive eye examinations during the Safety Follow-Up / Continuation Phase. Subjects who have not developed abnormal discoloration of the skin, lips, nails or mucosa will continue to undergo skin assessments by the investigator. Any subject who has developed abnormal discoloration of the skin, lips, nails or mucosa since baseline will be referred to a dermatologist for evaluation and 6-monthly follow up assessments. All subjects will continue to be followed until the pigmentation and/or discoloration has resolved or s