Sildenafil chemical structure

Since vardenafil has a very similar chemical structure to sildenafil, it is not surprising that it has a similar clinical profile. One study has reported no impairment of exercise ability in stable CAD patients receiving vardenafil 20 mg (49). Similar clinical efficiency for all three agents has been observed in patients with diabetes,... 

Fig. 7. Comparison of the chemical structures of (a) sildenafil (5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonyl-phenyl]-1-methyl-3-propyl-4H-pyrazolo[5,4-e]pyrimidin-7-one) and (b) vardenafil (2-[2-ethoxy-5-(4-ethylpiperazin-1-yl) sulfonylphenyl]-5-methyl-7-propyl-1 H-imidazo[5,1 -f][1,2,4]triazin-4-one) illustrates that these retain the bicyclic guanine core, but differ in the arrangement of nitrogen atoms. Comparison of the cocrystal structures of PDE5 in complex with sildenafil (PDB ID 2H42) and vardenafil (PDB ID 1UHO) shows that the binding mode of both sildenafil and vardenafil is similar to the binding mode of the guanine ring in the 5 -GMP complex. The interaction with the conserved Gln817 is shown.

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