Objective: To analyze the relationship between mean volume voided per micturition and number of daytime micturitions.
Methods: We reviewed data from randomized clinical trials on the medical treatment of overactive bladder published in the international literature between 1997 and 2004. Fourteen studies including data on these two parameters were identified.
Results: Six studies compared tolterodine with placebo, two tolterodine and oxybutynin with placebo, two tolterodine with oxybutynin, two solifenacin and tolterodine with placebo, one oxybutynin CR with oxybutynin IR, and one different doses of solifenacin. The correlation between the percent change in the mean voided volume and in the number of daytime micturitions was assessed using the Spearman rank correlation coefficient (r), with r=-0.67 for all the studies. For groups of patients treated with each drug, we found r=-0.09 for oxybutynin, r=-0.59 for tolterodine, r=-0.85 for solifenacin, and r=-0.34 for placebo.
Conclusion: The results of this analysis suggest that in the evaluation of the efficacy of a drug for overactive bladder, the mean volume voided per micturition may be a useful measure of efficacy.