viagra as far as i know comes in 25mg, 50mg, or 100mg tablets. if you have been prescribed the lowest dose it could be because your case is not considered to be a severe one. this is a good sign. either that or you are just being started off on a low dose to start off with.
i find it strange she never said anything to you about how to take them. there should definately be instructions on use and risks in the box. however there is really no science to it. just take one tablet about an hour before you want to attempt sex and you should feel the effects. side effects can include feeling flushed, dizzy, light headed, headaches. don't be alarmed if this happens. but if the side effects are really severe or something seek medical advice. don't take them if you have any heart problems. and it sounds a stupid thing to add, but dont ever take poppers with viaga because the combination can be fatal.
viagra worked successfully on my partner. however he did experience the dizzyness, and a feeling like being stoned. personally we never liked viagra that much. the side effects were too annoying. there is a different medecine available known as cialis. it has generic equivalents too which are cheaper and do the same thing. the active ingredient is a different chemical to the stuff that is used in viagra. cialis lasts longer and has no side effects so if you are looking to use sex drugs on any kind of regular basis you might want to look into it. feel free to pm me.
however be aware that in theory none of these treatments will work if your problem is psychological not physical. are relations between you and your wife good? could this be caused by nervousness? do you maintain an erection when you are masturbating?
i forgot to mention that erection dysfunction can often (especially as people get older) be a symptom of diabetes or indeed other underlying physical problems. this is worth checking out. viagra is not a long term solution. your problem should be addressed properly by your doctor.