Is it okay to mix codeine and Adderall?

It is generally a rule of thumb that you do not mix "uppers" (i.e. amphetamine, ephedrine, cocaine, etc.) with "downers" (i.e. diazepam, alprazolam, opiates, alcohol, etc.) as certain combinations of these substances can prove fatal. However, I have in the past taken hydrocodone and Adderall together for recreational purposes and suffered no ill effects. The key is to closely monitor how much you ingest, and to not go in search of a third substance once you are under the influence. I would recommend not drinking any alcohol and absolutely not taking a third substance, especially not a diazepam or alprazolam. Concisely, I'm not sure what your definition of "okay" is (most recreational prescription drug use is certainly not good for your overall health) but it certainly won't kill you if you keep your dosage reasonable.

The simple short answer is, YES! There is no evidence currently that states mixing amphetamines and opiates together can interact negatively.