Drug Interactions between aspirin / calcium carbonate and Tofranil-PM

MONITOR: Preliminary evidence suggests that aspirin may increase the plasma free concentration and pharmacologic effects of imipramine by displacing it from plasma protein binding sites. In 20 patients with endogenous depression given imipramine 150 mg/day for 5 days, administration of aspirin (500 mg every 12 hours for 2 days) decreased the plasma protein binding of imipramine from 84% to 72%. Additionally, the incidence of mild and severe adverse effects associated with imipramine increased nearly 60% and 150%, respectively. Other salicylates are expected to have similar effects due to their high affinity for plasma proteins.

MANAGEMENT: Pharmacologic response to imipramine should be monitored more closely whenever a salicylate is added to or withdrawn from therapy, and the imipramine dosage adjusted as necessary. Patients should be advised to notify their physician if they experience increased adverse effects of imipramine such as dry mouth, constipation, urinary retention, blurred vision, palpitations, and tachycardia.

Switch to consumer interaction data

MONITOR: Chronic administration of antacids may reduce serum salicylate concentrations in patients receiving large doses of aspirin or other salicylates. The mechanism involves reduction in salicylate renal tubular reabsorption due to urinary alkalinization by antacids, resulting in increased renal salicylate clearance. In three children treated with large doses of aspirin for rheumatic fever, serum salicylate levels declined 30% to 70% during coadministration with a magnesium and aluminum hydroxide antacid. Other studies have found similar, albeit less dramatic results. Antacids reportedly have no effect on the oral bioavailability of aspirin in healthy adults. However, administration of antacids containing either aluminum and magnesium hydroxide or calcium carbonate two hours before aspirin dosing led to reduced absorption of aspirin in uremic patients.

MANAGEMENT: Patients treated chronically with antacids (or oral medications that contain antacids such as didanosine buffered tablets or pediatric oral solution) 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.

Switch to consumer interaction data