Drug Interaction Report

MONITOR: Coadministration of pyrimethamine in doses exceeding 25 mg per week with trimethoprim or sulfonamides may increase the risk of megaloblastic anemia and pancytopenia. The proposed mechanism is additive antifolate effects.

MANAGEMENT: Periodic clinical and laboratory monitoring for signs of folic acid deficiency and hematologic changes is advisable.

ADJUST DOSING INTERVAL: Concomitant use of some oral medications may reduce the bioavailability of orally administered iron, and vice versa.

Food taken in conjunction with oral iron supplements may reduce the bioavailability of the iron. However, in many patients intolerable gastrointestinal side effects occur necessitating administration with food.

MANAGEMENT: Ideally, iron products should be taken on an empty stomach (i.e., at least 1 hour before or 2 hours after meals), but if this is not possible, administer with meals and monitor the patient more closely for a subtherapeutic effect. Some studies suggest administration of iron with ascorbic acid may enhance bioavailability. In addition, administration of oral iron products and some oral medications should be separated whenever the bioavailability of either agent may be decreased. Consult the product labeling for specific separation times and monitor clinical responses as appropriate.