Drotaverin is an isoquinoline derivative that exhibits spasmolytic effect on smooth muscle by suppressing the enzyme phosphodiesterase IV (PDE IV). Inhibition of the enzyme PDE IV leads to an increased concentration of cAMP, which inactivates the light chain of myosin kinase and leads to a relaxation of smooth muscle.
Drotaverin inhibits PDE IV in vitro without inhibiting the isoenzymes of PDE III and PDE V. To reduce the contractility of smooth muscle PDE IV is functionally very important and its selective PDE IV inhibitors may be useful in the treatment of hyperkinetic diseases and various symptoms caused by spastic conditions of the gastrointestinal tract.
Drotaverin does not have a side effect on the cardiovascular system, because in the cells of the smooth muscles of the myocardium and vessels, mainly contains isoenzyme
The enzyme that hydrolyses cAMP in smooth muscle cells of the myocardium and vessels is mainly isoenzyme of PDE III, which explains that drotaverin is an effective antispasmodic agent with no serious cardiovascular side effects and a strong cardiovascular therapeutic activity.
The drug is effective in spasms of smooth muscles of both nervous and muscular etiology. Regardless of the type of autonomic innervation, drotaverin acts on smooth muscles found in the gastrointestinal, biliary, urogenital and vascular systems.
Due to its vasodilating effect, it enhances the tissue circulation of the blood. Its effect is stronger than that of papaverine, and absorption is more rapid and complete, it binds less to plasma proteins. The advantage of drotaverin is that it does not have a stimulating effect on the respiratory system, which was observed after parenteral administration of papaverine.