Identification and local delivery of vasodilators for the reduction of ureteral contractions

Kidney stones and ureteral stents can cause ureteral colic and pain. By decreasing contractions in the ureter, clinically prescribed oral vasodilators may improve spontaneous stone passage rates and reduce the pain caused by ureteral stenting. We hypothesized that ureteral relaxation can be improved via the local administration of vasodilators and other smooth muscle relaxants. Here, by examining 18 candidate small molecules in an automated screening assay to determine the extent of ureteral relaxation, we show that the calcium channel blocker nifedipine and the Rho-kinase inhibitor ROCKi significantly relax human ureteral smooth muscle cells. We also show, by using ex vivo porcine ureter segments and sedated pigs that, with respect to the administration of a placebo, the local delivery of a clinically deployable formulation of the two drugs reduced ureteral contraction amplitude and frequency by 90% and 50%, respectively. Finally, we show that standard oral vasodilator therapy reduced contraction amplitude by only 50% and had a minimal effect on contraction frequency. Locally delivered ureteral relaxants therefore may improve ureter-related conditions. The local delivery of a calcium channel blocker and a Rho-kinase inhibitor, determined by screening for small molecules that cause ureteral relaxation, significantly reduce ureteral contraction in pigs.