I guess you have to question whether the result of the drug is worth the side effects. I've had a couple of drugs that have had that effect on me (one was a birth control that I swear works wonderfully simply because it kills any desire to have sex - depo provera).

Contact the same Doctor that wrote the script, and explain the lack of desire..

Anti Depressants can have the same effect.. BUT, there are a few things that can counter act the effects.. as well as a few herbal remedies that also work..