its actually more complicated, some foods to prevent absorption for some medications but there are also some foods which enhance absorption for some medicationsI have a theory consuming with food lowers bioavailability in that some of the drug will be absorbed in the food, excreted and never pass into the bloodstream, so I always try to have an empty stomach beforehand, could be completely wrong though
I fins my vyvanse works better taken with a protein rich well balanced meal with plenty of fats and carbs and salt
THC absorption is helped massively with fats, especially if the THC is dissolved in the fat ahead of time
the pharmacokinetics of many medications have been studied which is why you'll get recommendations from your Dr or pharmacist or it says on the bottle "take with meal" or whatever it is
many foods dont impact absorption of some meds at all
its a pretty complicated question of transport of the drug across the cell membrane, does it diffuse or is it actively transported? does it need a certain ionization state? does the food contain something that competes with active transport? enhances it?