Sildenafil Citrate - Impurity B

1094598-75-0

1-Methyl-4-[[4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d] pyrimidin-5-yl)phenyl]sulfonyl]piperazine-1-oxide; 5-[2-Ethoxy-5-[(4-methyl-4-oxido-1-piperazinyl)sulfonyl]phenyl]-1,6-dihydro-1-methyl-3-propyl-7H-pyrazolo[4,3-d]pyrimidin-7-one; Sildenafil N-Oxide; 1-{[3-(6,7-Dihydro-1-methyl-7-oxo-3-propyl-1H -pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl}-4-methylpiperazine N4-oxide (USP);