Drug Interactions between Apetimar with Iron and aspirin/citric acid/sodium bicarbonate

MONITOR: Agents that cause urinary alkalinization can reduce serum salicylate concentrations in patients receiving anti-inflammatory dosages of aspirin or other salicylates. The mechanism involves reduction in salicylate renal tubular reabsorption due to increased urinary pH, resulting in increased renal salicylate clearance especially above urine pH of 7. This interaction is sometimes exploited in the treatment of salicylate toxicity.

MANAGEMENT: Patients treated chronically with urinary alkalinizers and large doses of salicylates (i.e. 3 g/day or more) should be monitored for potentially diminished or inadequate analgesic and anti-inflammatory effects, and the salicylate dosage adjusted if necessary.

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ADJUST DOSING INTERVAL: The bioavailability of orally administered iron may be reduced by concomitant administration of antacids or other agents with acid-neutralizing effects. The exact mechanism is unknown but may involve reduced iron solubility due to increase in gastric pH and/or reduced absorption due to complexation or precipitation of the iron. Based on existing data, sodium bicarbonate and calcium carbonate appear to have greater effects than antacids containing magnesium and aluminum hydroxides. In a study of patients with mild iron deficiency anemia, coadministration of ferrous sulfate with sodium bicarbonate 1 gram and calcium carbonate 500 mg reduced iron absorption by 50% and 67%, respectively, while 5 mL of an antacid containing magnesium and aluminum hydroxides had little effect. Another study also found no effect on iron absorption when ferrous sulfate (equivalent to 10 mg/kg of elemental iron) was coadministered with magnesium hydroxide (1 mg for every 5 mg of elemental iron ingested) in a group of healthy, fasting male subjects. In contrast, absorption of iron from ferrous sulfate and ferrous fumarate tablets was reduced by 37% and 31%, respectively, following administration of an antacid containing magnesium carbonate, magnesium hydroxide, and aluminum hydroxide in a study of healthy, iron-replete volunteers. Similarly, in a study of nine patients, coadministration of 5 mg of ferrous sulfate with a 35 gram dose of magnesium trisilicate was found to reduce iron absorption by an average of more than 70%. The interaction reportedly does not occur in the presence of ascorbic acid, which may competitively bind with iron and prevent the interference with iron absorption.

MANAGEMENT: To minimize the potential for interaction, it may be appropriate to administer oral iron preparations at least two hours apart from antacids or other agents with acid-neutralizing effects.

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