A Randomized Multicenter Double-Blind CT to Evaluate the Efficacy and Safety of Mycophenolate Mofetil . . .

Inclusion Criteria: * Participant at least 18 years of age and received a diagnosis of PBS/IC, confirmed by cystoscopy and hydrodistention in the past with findings of glomerulations and/or ulceration. * Participant has symptoms of urinary frequency and pain/discomfort (at least 4 on each 0-10 Likert scale) at entry. * Participant failed at least 24 weeks of active treatment with a minimum of 3 standard forms of therapy (including hydrodistension) or combination of therapies for PBS/IC. * Participant will receive cystoscopy to be performed in the office at baseline visit before randomization if none has been conducted within the previous 24 weeks. Cystoscopy results must show no unevaluated lesions. * Female participants with a cervix are required to have Pap smear exam within the past 12 months prior to enrollment with normal results reported. * Participant (female) with child-bearing potential must agree to use two reliable/medically approved methods of birth control. Exclusion Criteria: * History of cancer or known pre-malignant conditions, including skin cancer. * History of bladder calculus, tuberculous cystitis; neurologic disease affecting bladder function. * Current immunocompromised condition, including current or chronic treatment with immunosuppressive agents, or known positive for HIV (positive antibody confirmed by Western Blot or IFA); active tuberculosis requiring on-going therapy; current systemic steroid treatment at any dose. * Liver function test or creatinine results greater than 2x the upper limit of normal at home institution laboratory. * Any baseline leukopenia (an absolute neutrophil count \<1,500/µL), thrombocytopenia (a platelet count less than 150,000/microL), or anemia - HGB \< 12 or \< 11 g/dLin men and in women respectively. * Is seropositive for Hepatitis B surface antigen; or is seropositive for Hepatitis B surface antibody (if not previously vaccinated); is seropositive for Hepatitis C antibody or HIV antigen or antibody. * Allergy or hypersensitivity to study medication. * Unable to void spontaneously. * Active urethral or ureteral calculi, urethral diverticulum. * Any severe debilitating or urgent concurrent medical condition. * Previous cytoxan/cyclophosphamide treatment, pelvic radiation therapy; augmentation cystoplasty, cystectomy, or cystolysis; neurectomy. * Participants with history of treatment for genital tract dysplasia or genital warts or genital herpes. * Patients with active or a history of peptic ulcer disease, inflammatory bowel disease or gastrointestinal bleeding. * Patients with hypertension not adequately controlled with medication. * Patient currently taking H2 blockers or proton pump inhibitors. * Patients who cannot tolerate or refuse an office cystoscopy. Exclusion criteria for men only: * Currently being treated for chronic bacterial prostatitis, as documented by a positive urine culture or prior history of recurrent bacterial urinary infections. * Unevaluated suspicious prostate exam. Exclusion criteria for women only: * Lactation, pregnancy, or refusal of two types of (medically approved/reliable) birth control in women of child-bearing potential. * Pain, frequency, urgency symptoms present only during menses.