4cfc52b1__for_Professionals___Drugs_com__Interaction
[Drug or Test] Antacids, calcium-containing [Comments] Ingestion times of phenytoin and antacid preparations containing calcium should be staggered in patients with low serum phenytoin concentrations to prevent absorption problemsb [Interaction] 
Calcium ions interfere with GI absorption of phenytoinb
Phenytoin Sodium Monograph for Professionals - Drugs.com
Interaction