Antispasmodic, isoquinoline derivative. It has a powerful antispasmodic effect on smooth muscle due to inhibition of the type 4 PDE enzyme (PDE4). Inhibition of PDE4 leads to an increase in the concentration of cAMP, inactivation of the kinase of the light chain of myosin, which further causes the relaxation of smooth muscles. The effect of drotaverine, which reduces the concentration of the Ca2 + ion through cAMP, explains the antagonistic effect of drotaverine in relation to Ca2 +. In vitro, drotaverin inhibits PDE4 isoenzyme without inhibiting PDE3 and PDE5 isoenzymes. Therefore, the effectiveness of drotaverine depends on the concentration of PDE4 in different tissues. PDE4 is most important for suppressing the contractile activity of smooth muscles, and therefore selective inhibition of PDE4 may be useful for the treatment of hyperkinetic dyskinesias and various diseases involving the spastic state of the gastrointestinal tract. Hydrolysis of cAMP in the myocardium and vascular smooth muscle occurs mainly with the help of PDE3 isoenzyme, which explains the fact that with high antispasmodic activity in Drotaverine there are no serious side effects from the heart and vessels and pronounced effects on the cardiovascular system. Drotaverinum is effective in spasms of smooth muscles of both neurogenic and muscular origin. Regardless of the type of vegetative innervation, Drotaverinum relaxes the smooth muscles of the gastrointestinal tract, the biliary tract, and the urogenital system. Due to its vasodilating action, drotaverin improves blood circulation in tissues. Thus, the above-described mechanisms of action of Drotaverine eliminate spasm of smooth muscles, which leads to a decrease in pain.