If you take the alprazolam via the sublingual route (which tastes like relief by the way) then it doesn't matter whether you've eaten, absorption will not be affected, it will even be slightly more complete than oral administration with higher peak serum / blood concentration levels with sublingual alprazolam. On the other hand, food is not usually something that affects benzodiazepines mechanism's of action. Sometimes there's a slight delay in Cmax or a usual Area Under Curve, to explain the pharmacokinetics a little bit.
So food + benzodiazepines = not a problem, and will kick in in 5-10 minutes if you sublingual the alprazolam peak concentrations usually skyrocket in an hour or less.
Benzodiazepines + Smoking Cigarettes = Some studies have shown up to 50% reductions in benzodiazepine serum levels / concentration reduced by half upon exposure to cigarette smoke.
I can verify from subjective experience that smoking cigarettes pretty much renders most benzodiazepines ineffective. I'm sure part of this may be placebo, but the thing is with my benzodiazepines, I noticed extremely rapidly diminishing effects of the benzodiazepine whenever I give in to having a cigarette (which thank heavens is not often anymore) and because I don't take benzodiazepines recreationally (as in, because I only take them as directed for panic disorder and insomnia), I think that I, and others who have legitimate mental illnesses warranting benzodiazepine therapy particularly can be sensitive to the diminishing effect cigarettes have on benzodiazepines because instead of "feeling less fucked up" or whatever, we experience rebound anxiety/insomnia/panic/etc due to your liver metabolizing the alprazolam at a very rapid rate.
I'm not sure which of the 5000 chemicals/ingredients in cigarettes is responsible for this, I've read tons of studies discussing benzos vs cigs but never more specific than just "cigarette smoke". This leads to my question, does nicotine have any effect on the metabolism of benzodiazepines, or is the decrease in benzodiazepine concentrations due to one or more of the thousands of carcinogens, Poly Aromatic Hydrocarbons (PAHs), etc?? This I do not know.
However, in conclusion, out of all the people I know who take benzodiazepines (which include like.... 50% or more of my homies), 90% of the time when I have asked them "Do you ever feel like smoking cigarettes has any effect on how you feel benzodiazepines?" 90% of the people I ask answer something like:
YES: DECREASED BENZODIAZEPINE EFFICACY AND DURATION UPON CIGARETTE SMOKE INHALATION.
And mind you, this is before I have shown them or told them about any of the peer reviewed articles that support the notion that smoking cigarettes can cause up to a 50% reduction in the benzodiazepine concentration levels, the article I'm thinking of in particular used alprazolam in their study, so you should google "Alprazolam AND smoking AND cigarettes AND pubmed" without the quotations to read the literature I'm talking about. I've posted links to these studies so many times I should have them bookmarked, but I don't so I'm sorry I won't be leaving a direct link to something you guys can easily find with a search engine.
Keep in mind that everyone reacts differently! I've met two people so far who insist that smoking cigarettes doesn't effect their benzodiazepine experience, but the general consensus is that smoking cigarettes not only causes cancer, emphysema, COPD, heart attack, stroke, etc, but it also cockblocks your benzos. Yet another reason to quit smoking cancer sticks.
$0.02
