Some, but not all studies have shown that
antacids (containing aluminium, calcium or magnesium) do not usually interact to a clinically relevant extent with
phenytoin. However, in some instances
antacids have reduced
phenytoin serum levels and this may have been responsible for some loss of seizure
control in a few patients.
Concurrent use need not be avoided but if there is any hint that an epileptic patient is being affected by this interaction, separating the dosages by 2 to 3 hours may minimise the effects.