If it's just for acid reflux (not for an ulcer or anything) there shouldn't be any harm just skipping it on the day you want to trip just to be extra safe
1p-LSD is generally considered to be nothing more than a pro-drug for LSD. Changes in stomach pH may have minor effects on the hydrolysis of the 1-propionyl-group in the stomach, but realistically the same reaction should also happen in your blood, and probably faster at that due to enzymatic catalysis (after all, most people prefer to keep tabs pressed against their cheek/under the tongue anyway, bypassing the stomach via buccal/sublingual absorption).