Phosphodiesterases (PDEs) are enzymes that catalyze the hydrolysis of the 3′ cyclic phosphate bond of cyclic nucleotides. PDEs can break a phosphodiester bond. Usually, people speaking of PDE are referring to cyclic nucleotide PDEs. However, there are many other families of PDEs, including phospholipases C and D, autotaxin, sphingomyelin PDE, DNases, RNases, and restriction endonucleases, as well as numerous less-well-characterized small-molecule PDEs. The cyclic nucleotide PDEs degrade the phosphodiester bond in the second messenger molecules cAMP and cGMP. They regulate the localization, duration, and amplitude of cyclic nucleotide signaling within subcellular domains. PDEs are therefore important regulators of signal transduction mediated by these second messenger molecules.

Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are important second messengers in signaling. They play an important role in cell proliferation, cell-cycle regulation, and metabolic function. Activated adenylyl-cyclase and guanylyl-cyclase catalyze the conversion of ATP and GTP to cAMP and cGMP, respectively. Inactivating molecular defects in PDEs lead to high cAMP or cGMP levels that in turn generate a continuous activation of the cAMP/PKA cascade.

Flavoxate, a flavone derivative, is a potent and competitive PDE inhibitor. Meanwhile, Flavoxate is an inhibitor of L-type calcium channels and an antimuscarinic agent. Flavoxate exhibits potent antispasmodic effects. Its muscle relaxant properties may be due to a direct action on the smooth muscle rather than by antagonizing muscarinic receptors. Flavoxate is effective in the symptomatic relief of the lack of muscle control in the bladder, such as dysuria, urgency, and nocturia. Flavoxate is generally well tolerated. However, it can potentially cause vomiting, upset stomach, and dry mouth or throat.

All in all, Flavoxate is an inhibitor of PDE and L-type calcium channels, and an antimuscarinic agent. Flavoxate exhibits potent antispasmodic effects.


Levy I, et, al. Curr Opin Pharmacol. 2011 Dec;11(6):689-97.