Trapidil

Trapidil is thought to inhibit cyclic adenosine monophosphate (cAMP) phosphodiesterase enzymes. The resultant increase in cAMP potentiates the inhibition of platelets by adenosine. The reduction in platelet activation is likely responsible for the decrease in thromboxane A2 generation seen with trapidil. The increase in cAMP is also likely responsible for the vasdilatory action of trapidil. The increase in protein kinase A activity due to increased cAMP activated L-type calcium channels in the heart leading to increased depolarization and a positive inotropic effect. Lastly, PKA inactivates Raf-1, an activator of mitogen activated protein kinase (MAPK), which leads to a reduction in MAPK activation. This reduction in MAPK prevents mitogenesis due to PDGF binding to PDGF receptors.