Michael, Your question is very ill-defined. I regularly partake in a drug that lowers my IQ in exchange for other utility... It's called alcohol. If you are talking about permanent IQ reductions, I would need to have some sense of what losing one IQ point felt like before I could evaluate a trade. Is it like taking one shot? Would I even notice it missing?

Many psychotropic drugs, especially antipsychotics, 'slow' down the people that take them and thus could be associated with lowering IQ, yet many people choose to take them and lower their IQ for the utility gained by not hearing demonic voices or being allowed to leave a mental institution.