I haven't tried Viagra. My therapist actually mentioned this when we discussed the situation. I assume you take it before sex.
Yep, just like you normally would. One hour before.
For me it works VERY WELL! I've found that if you feel the typical flush that comes with viagra, it's more guarranteed to work (for POIS prevention)
I think that regular users of viagra may not get the flush at usual doses. I started at 25 mg (half a pill) and now it has stabilized at about 50 mg.
I may have to up that another 25 to be on the safe side.
Another guage for me is the erection, but I'm older so I need a bit of "help". As such, I notice when it's working well. Younger people already
get good erections, so this may not be as much of a guide.
I would say, try to find a minimum dosage that works consistently, because I don't know, perhaps taking more may desensitize you more quickly.
BTW, follow all of the regular viagra precautions.