Iso Sildenafil

Chemical Name: 5-[2-Ethoxy-5-[(4-methyl-1-piperazinyl)sulfonyl]phenyl]-2,6-dihydro-2-methyl-3-propyl-7H-pyrazolo[4,3-d]pyrimidin-7-one; 1-[[3-(4,7-Dihydro-2-methyl-7-oxo-3-propyl-2H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine;