Drotaverin is an isoquinoline derivative that exhibits spasmolytic effect on smooth muscle by inhibiting the enzyme phosphodiesterase 4 (PDE-4). Inhibition of the enzyme PDE-4 leads to an increase in the concentration of cyclic adenosine monophosphate (cAMP), which inactivates a light chain of myosin kinase (MLCK), which, in turn, leads to relaxation of smooth muscles.
Drotaverin inhibits the enzyme PDE-4 in vitro without inhibiting the isoenzymes PDE-3 and PDE-5.Apparently, PDE-4 is functionally very important for reducing the contractility of smooth muscles, so selective PDE-4 inhibitors can be effective in the treatment of hyperkinetic diseases and diseases associated with spastic conditions of the gastrointestinal tract (GI tract).
The enzyme that hydrolyses cAMP in smooth muscle cells of the myocardium and vessels is mainly an isoenzyme of PDE-3, which explains the high effectiveness of drotaverin as an antispasmodic in the absence of pronounced effects on the cardiovascular system and serious cardiovascular adverse reactions.
Drotaverine is effective in spasms of smooth muscles of both nervous and muscular etiology. Regardless of the type of autonomic innervation drotaverine acts on the smooth muscles of the gastrointestinal tract, bile ducts, as well as genitourinary and vascular systems. Due to the vasodilating action drotaverine improves the blood supply of tissues.