Mirabegron: A Novel and Promising Medical Expulsive Treatment for Ureteral Stones?

Medical expulsive therapy (MET) is used especially in distal ureteral stones to reduce colics and decrease the number of endourological surgical interventions. A broad spectrum of agents can be used for the relaxation and the dilatation of the ureter, reducing the intraureteric pressure. Alfa-blockers, calcium channel blockers, phosphodiesterase (PDE) inhibitors, and spasmolytics have been shown as effective in clinical trials on urolithiasis. It is a fact that the urothelium itself, the interstitial cells and the ureteric smooth muscle, have B-beta-2 and beta-3 adrenoreceptors. Stimulation of these receptors results in relaxation of the ureter. A recent beta-3 agonist, mirabegron, is commonly used for overactive bladder nowadays. The mechanism of action is adrenergic agonism that affects with the storage phase of the bladder, without interfering the voiding phase, which is regulated by parasympathetic pathways, commonly muscarinic. Agonism of the beta-3 receptors in the ureter has been shown to decrease the intraluminal pressure. By this mechanism, mirabegron can be thought as an alternative MET agent. Acting through different pathways, and having low adverse effect profile, can be thought as the most striking advantages of mirabegron as a MET. In vitro and in vivo trials should be conducted to support this hypothesis.