RecruitingPhase 2Drug trialZinc Supplementation With Botulinum Toxin for Overactive BladderThis randomized, double-blind, placebo-controlled trial evaluates whether oral zinc plus phytase supplementation modifies clinical response to intradetrusor botulinum toxin injection in patients with overactive bladder. Participants will receive either zinc plus phytase supplementation or matching placebo for five days prior to intradetrusor botulinum toxin injection. Participants will be followed for six months after treatment to assess need for repeat botulinum toxin injection, urinary symptoms, and patient-reported outcomes related to overactive bladder.