Well, Protector of Mankind- where shall we begin? On the neurological side, a drug constantly causing orgasms is almost certain to be terribly addictive (not to mention sticky) - a rather large amount of dopamine is secreted in the nucleus accumbens as a result of messages sent from the VTA (and I don't know enough about orgasms to track it back from there) - this reinforces behavior (not exactly the same as fun, but they often come together) and is what causes many groups of drugs to be addictive.

From the manufacturing point of view, I'm not so sure this is possible either. I'm sure you'd be willing to skip the genital contractions and secretions, both for the sake of your poor little muscles and glands, and for the sake of your laundry. So we want to stop some acetylcholinergic activities, and perhaps prevent some of the secretion of oxytocin. I'm not a pharmacist, a biologist or a psychiatrist*, but getting these effects focused on the lower part of your body while still getting all the desired affects mentally sounds near impossible to me.

Besides - think about all the effects on the social level…

* Any comments by experts are welcome !