There is another factor to consider. Some drugs are only active – or are more active – when they are in a slightly different formulation. For instance, cocaine, and nicotine, both are more active in their base salt form than in their acid form. Adding something to increase the pH (thus less acidic) can make them more powerful. For cigarettes, they add ammonia I believe. For cocaine, baking soda and a couple other things makes crack. The main effect in both cases is to change the pH.
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