Efficacy and Safety of Gabapentin in Treating Overactive Bladder

Inclusion Criteria: * Ambulatory and able to use the toilet without difficulty * History of OAB symptoms for ≥ 3 months * An average of ≥ 8 micturitions per 24 hours and ≥ 1 urgency episode (with or without incontinence) per 24 hours as documented in a 3-day micturition diary * Subjects are bothered by symptoms as reflected by OAB-questionnaire Exclusion Criteria: * Patient has stress or mixed incontinence * Patient has Benign Prostatic Hyperplasia with severe lower urinary tract symptoms based on IPSS score * Patient has uncontrolled Diabetes Mellitus Type II Patient has Diabetes Insipidus, UTI * Patient has history of interstitial cystitis, painful bladder syndrome, or chronic pelvic pain * Patient has a history of stroke, seizures, or major neurological disorders * Patient has a history of fecal incontinence and or continual urine leakage * Patient has had surgery to correct stress urinary incontinence or pelvic organ prolapse within 6 months of study start * Patient received bladder training of electrostimulation within 2 weeks of study start * Patient requires a catheter * Patient is taking medications that cannot be stopped for the duration of the trial including certain anticholinergics or smooth muscle relaxants * Patient began taking tricyclic antidepressants, serotonin/norepinephrine reuptake inhibitors, calcium channel blockers, ephedrine/pseudoephedrine, or diuretic therapy less than 8 weeks before study start * Patient has been on hormone replacement therapy for less than 12 weeks at study start * Patient must take medication for arrhythmia, contraindicated for Solifenacin or Gabapentin * Patient has multiple and/or severe allergies to foods and drugs * Patient regularly uses any illegal drugs