There are only seven SSRI's: [DLMURL]http://www.ptsdforum.org/c/wiki/selective-serotonin-reuptake-inhibitor/[/DLMURL]
The brand names are really quite irrelevant, as the primary ingredient is one of the seven.
You then have a range of other drugs, not SSRI's, such as SNRI's, MAOI's, Tricyclics, etc, all of which contain further sub-groups of medications, and they do different things.
Drugs may simply do nothing for you... as they don't work for everyone. Physicians also have to play the trial and error game on a patient by patient basis, as they have no way to determine what medication will work for you, if any at all. They start with the safest usually, being SSRI's, then work their way outwards. Its not really that others aren't safe, but more they come with different side effects, and some are addictive, which create far worse issues all by itself, ie. Valium, Xanax, etc.