The extent of absorption of drugs - i.e. the area under a plasma concentration versus time graph - is rarely affected by anything. More often it is only rate that is affected.
Extent may be influenced by the use of chelating compounds, an example of which is tetracyclines and milk or antacids - in fact anything containing divalent and trivalent cations. It is the direct contact that is important.
Another example is L-dopa and amino acids in the diet, to the extent that a low protein diet may reduce problems in on-off Parkinson's disease.
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