There should be a paper that comes with your medicine that explains the effect of taking the drug postprandial (after food) or while fasting (before food), plasma concentration vs time.
for my medicine (pariet), if one takes before food, the onset of effect is faster, it reaches peak faster, and the effect gradually wears off. if one takes after food, the onset is slower, reaches peak slower (by a few hours), but it wears off with a higher plasma concentration.
for me, my reflux occurs mostly at night, I should be taking it after dinner, but the doctor doesn't know the difference, so i am stuck with taking it before dinner.
talk to your doctor about the difference, before you start.