PDE5 inhibitor

Phosphodiesterase -5 inhibitors (including phosphodiesterase V inhibitors, PDE -5 ) inhibitors are substances that inhibit the cGMP - degrading enzyme phosphodiesterase V and thus increase the concentration of intracellular cGMP (cyclic guanosine monophosphate ). They cause among other things, a dilation of blood vessels ( vasodilation ). Phosphodiesterase -5 inhibitors were originally developed for the treatment of angina pectoris, but found today in the treatment of erectile dysfunction and in the treatment of pulmonary hypertension application. PDE -5 inhibitors are available by prescription.

Mechanism of Action

Phosphodiesterase -5 inhibitors are inhibitors of phosphodiesterase V, an enzyme from the group of phosphodiesterases. Phosphodiesterases are responsible for the degradation of intracellular messengers ( second messenger ) cyclic adenosine monophosphate ( cAMP) and cyclic guanosine monophosphate (cGMP). Phosphodiesterase V is able to selectively degrade cyclic GMP. in turn, the cGMP second messenger, which is activated by the endothelial relaxing factor, nitric oxide ( NO) and is thus involved in the relaxation of blood vessels. Since phosphodiesterase -5 inhibitors inhibit the inactivation of cGMP, they lead to a strengthening of the vasodilator effect of nitric oxide.

The effect of phosphodiesterase -5 inhibitors can be observed especially in tissues which express the phosphodiesterase V strong. These include, in addition to the smooth muscle of blood vessels, where phosphodiesterase -5 inhibitors lead to a relaxation, and the lung tissue and platelets. Of particular interest to the pharmaceutical industry, the indication erectile dysfunction, on the relaxant effect on supplying the erectile tissue of the penis is due to blood vessels and thus facilitating erection.

Substances

Due to the selectivity for the isoform of phosphodiesterase V can be made between non-selective phosphodiesterase inhibitors, such as the methylxanthines caffeine, theophylline, theobromine, inhibit nonspecific different phosphodiesterases and selective inhibitors of phosphodiesterase V, such as sildenafil ( Viagra), tadalafil ( Cialis), vardenafil (Levitra ) and Avanafil ( Spedra, re-authorized in 2013 ).

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