Like "clay, The nitro tablets are fast-acting (1-3 minutes) with a shorter duration (under 30 minutes) and work directly in the heart by providing additional nitric oxide. Viagra (and it competitors) work differently. They inhibit an enzyme that blocks the action of natural nitric oxide (none is actually added as with nitro), it acts more slowly, lasts longer, and - this is important - primarily affects receptors in the corpus cavernosum of the penis. While Viagra was originally developed as a heart drug and is known to magnify the lowering of blood pressure when taking nitro, it is unlikely to provide the kind of relief that nitro will. As always, talk to your doc as the info here is simply for discussion puposes and can never be a replacement for professional advice. HH"