One such study was conducted in 2005 by Parsons et al., which tested the efficacy of heparin combined with intravesical lidocaine in 47 newly diagnosed IC patients. 75% of patients reported significant improvement in symptoms after just one instillation with symptomatic relief lasting at least 4 hours. Significant improvement in symptoms was reported in 94% of patients who received a second instillation using a higher concentration of lidocaine. Of 20 patients who received a course of 6 instillations over 2 weeks, 80% reported sustained relief15.