A lot of information can be found on the various Health related websites.
The various ED drugs may or may not work with every individual. And a particular dose for one fellow may be too much or not enough for another. They may also work for a while and some months later have no or little effect. Your doctor is the best person with whom to discuss these medications.
A not uncommon experience with Viagra is, after about twenty minutes, a rock solid erection for a couple of hours. Even if one ejaculates too soon, Viagra will keep you in shape until your partner has her orgasm. After the first shot and about ten minutes you are good to go again. Side effects include blue tinted vision when the drug takes hold and after it is done, a subsequent headache. Also for some, the longlife boner may translate into a mission to merely pound away, rather than be in some connection with your partner, whether she be a SO or a transient experience.
Viagra does not particularly care if you are in the mood, so be in the mood and with opportunity when you take it, else you have a hard-on with little motivation. Other drugs' activity are mood encouraged, such as Cialis, which also has a latency of 24 to 48 hours.
Your urologist may be able to precribe an injectible which has fewer side effects, reliable performance and less cost than the pills, but then there is the aspect of it being injectible which provides an obstacle for those queasy about needles. For the hardcore situation, there is surgery.
All ED solutions are by prescription for those who have the medical need for them. Use by those not medically requiring them is inadvisable.
Written with files from everywhere.