I hear you, but the problem with all drugs (including sleeping tablets) is that they are a short term fix, and they have side effects. You're essentially surrendering control of your body to a pharmaceutical company when you start taking this stuff.
The longer you take them, the more dependent you are, and the harder it becomes to manage without them. Eventually, you have to take more and more just to get the same level of performance.
There could be any number of reasons you're having trouble concentrating - lifestyle, diet, sleep, emotional disturbance, willpower. Any of those are correctable if you find out what they are. By just taking drugs to deal with it, you're masking the real problem without getting to the bottom of the situation.
Viagra isn't a very good comparison (it was an offhand comment by me). It's more like taking anabolic steroids to put muscle on. Sure, you'll look better quicker, but you're storing up big problems for later, and as soon as you stop, you'll lose the muscle again.
I'm not totally anti meds. I believe that when used judiciously, they can help with problems over the short term. I know several people who have been helped over severe depressive episodes by taking SSRIs, to a point where they could benefit from therapy, and have got their lives back on track.
The big danger comes when they are marketed as "lifestyle medications", to be taken over an indefinite period. Spending your entire life dependent on one substance or other in order to function is a very poor existence indeed.
You should watch Generation Rx if you haven't seen it already:
'GENERATION RX' Extended Trailer - YouTube