There are several different approaches. The most common are prostaglandins, Viagra and Muse. Prostaglandins are the cheapest and Muse is the most expensive. Viagra can be cheaper than prostaglandins, but only if you can get away with a small dose of 25 or 50 mg, a fraction of the usual 100 mg. pill.

1. You might choose prostaglandins when economics are a concern, you want a guaranteed erection whether or not you are turned on, or when other methods have failed. The drawback is you must inject the drug into your penis. This is not painful. You can barely feel it. A spring loaded device called a PRO-Ject holds the syringe and gives you a poke that feels like a finger snapping against your penis. You then press the plunger to inject only a microscopic amount (0.3 ml) through the extremely fine needle. You can’t feel that at all. It can be a bit embarrassing to have to excuse yourself just before sex starts to "shoot up" If anyone sees what you are doing they may be alarmed you are taking some street drug, or may just be freaked by the needle and lose interest in sex. Depending on the dose you choose, you can create as hard and as long an erection as you want. The catch is, there is no way it will go down prematurely, even if you come. It is great for building self confidence. You have a guaranteed erection, no matter what you do or think. If you go to a steambath with it, you will attract a fair bit of unwanted attention from suitors who mistake your erection for sexual interest in them. On the other hand, I found cute guys who turned me down in past, suddenly were pursuing me. The medication must be kept refrigerated or on ice which makes it slightly more complicated to use away from home. You can carry a single dose with you in a syringe in a rigid eyeglass case to ensure the plunger does not get accidentally pressed, and pack it next to a frozen gel pack. That will keep for about a day. You can’t very well take it with you for extended travel, say on some sex-based vacation. It may be my imagination, but I’d swear the stuff is also an aphrodisiac.
2. You might choose Viagra when you want a completely natural hard on. With Viagra, you won’t notice anything at all until you actually start sex. Your plumbing just works normally. The effect is gentle. Viagra sensitises the nerves so that takes much less stimulation to get you going. The effect lasts about two hours. You may get and lose your erection perfectly normally during that time. The catch is you can’t tell when it has worn off. You may start something and not be able to follow through. The other catch is it only works on 50% of men. Viagra has no effect on sexual desire.
3. You might choose Muse when you are squeamish about needles. You pee then you insert a pellet about 4 cm (1.6 in) into the urethra using a special applicator. The pellet dissolves in the residual urine and goes into the bloodstream.