Drugs in this class are Prozac(fluoxetine), Zoloft (setraline), Lexapro (escitalopram) and many more. I've had the experience of using Prozac and Zoloft. I found that within two weeks, my ability to get an erection was nearly gone.
I've heard that other indidivuals who tried to have sex/masturbate on these drugs found that their orgasms were 'dulled' and just not as pleasant as when not on the drug.
There is a theory I've read about of serotonin being the "breaks" in sexual drive, and dopamine being the "gas/accelerator". Could someone explain if this is the reason?