What happens when you mix a stimulant and a depressant?

mixing stimulant and depressant can have varying effects, most common is actually nausea, not only is this harmful for your body, but your brain is at the greatest risk. Depending on the mix, there is a chance that you can be stimulated or even exhausted depending on the concentration and the drug delivery system itself unique to each and every drug, all drug delivery system vary, mixing the two will cause the drug delivery system of these two class of drugs to conflict, its like shooting in the dark, because you will not know which will take effect, if one will begin and then gets suppressed by the other, or whether the drug itself will not the proper conditions/environment for its drug delivery system to be fulfilled and become ineffective all together.