At the very least 24 hours should pass in between both amounts of Sildenafil.
It works by obstructing a specific enzyme tasked with blood outflow from the tissues of the penis. Nowadays it is not uncommon for people to purchase their Sildenafil online, as this is a much less expensive way to get the drugs called for.
Talk to your doctor about possible side effects in your situation to ensure the advantages outweigh the potential risks.
Sildenafil needs to be taken half a hr prior to having sex, although some people could need longer to reply to the medicine and experience its perks.