Drug Interaction Report

Aspirin and Aluminum Phosphate: Interaction Details

A pharmacist-reviewed analysis of the Aspirin and Aluminum Phosphate interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Aspirin

Acuprin® Anacin Aspirin Regimen Anacin® Aspirin Regimen Ascriptin® Aspergum Aspergum® Aspi-Cor Aspidrox®
+

Aluminum Phosphate

No brand names on record
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Jul 11, 2026
Editorial policy · Data sources
LinkedIn
Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 465 documented Aspirin interactions, 124 are rated moderate — including this one.
Onset
delayed
Evidence
theoretical
Severity
Moderate

What happens

Decreased salicylate effectiveness

Interaction Deep Dive

Routine administration of aluminum, calcium or magnesium containing products has been reported to increase urinary pH significantly enough to increase the renal elimination of salicylates, decreasing salicylate concentrations by 30 to 70%67.

Why it happens (mechanism)

Increased renal clearance and decreased absorption (due to increased urinary pH)

Literature reports

2 reports — tap to read

a) Concomitant aspirin and antacid therapy has been reported to result in lowering of serum salicylate levels, either secondary to a decrease in renal tubular reabsorption of salicylate or increasing gastric emptying of enteric coated tablets causing earlier or more rapid release of aspirin in the intestine 1234.

b) In a pilot study with 5 uremic patients, aluminum-magnesium and calcium antacids were shown to decrease aspirin absorption. Salicylate serum levels were lowest if aspirin was given 2 hours after antacid ingestion compared to salicylate levels achieved after simultaneous administration. Maximum salicylate levels were reduced by 50% to 70% by administration of antacids 5.

Common questions

Can I take Aspirin and Aluminum Phosphate together?

Decreased salicylate effectiveness Always confirm with your pharmacist or prescriber before making any change.

How serious is the Aspirin and Aluminum Phosphate interaction?

It is rated moderate. Can be significant — usually manageable with monitoring.

How quickly could this interaction happen?

The documented onset is "delayed". Effects tend to build up gradually over days to weeks.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Aspirin or Aluminum Phosphate need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there anything you'd monitor while I'm on both?

References (7)

  1. Feldman S & Carlstedt BC: Effects of antacid on absorption of enteric-coated aspirin. JAMA 1974; 227:660.
  2. Levy G, Lampman T, Kamath BL, et al: Decreased serum salicylate concentrations in children with rheumatic fever treated with antacids. N Engl J Med 1975; 293:323. DOI
  3. Strickland-Hodge B, Thomas TR, Gould WA, et al: The effects of antacids on enteric-coated salicylate preparations. Rheumatol Rehabil 1976; 15:148-152. PubMed
  4. Shastri RA: Effect of antacids on salicylate kinetics. Int J Clin Pharmacol Ther Toxicol 1985; 23:480-484.
  5. Gaspari F, Vigano G, Tocatelli M, et al: Influence of antacid administrations on aspirin absorption in patients with chronic renal failure on maintenance hemodialysis. Am J Kidney Dis 1988; 11:338-342. PubMed
  6. Gibaldi M, Grundhofer B, & Levy G: Effect of antacids on pH of urine. Clin Pharmacol Ther 1974; 16:520-525. DOI
  7. Hansten PD & Hayton WL: Effect of antacid and ascorbic acid on serum salicylate concentration. J Clin Pharmacol 1980; 20:326-331. PubMed
Was this write-up helpful?
Aspirin

Keep reading about Aspirin

All Aspirin interactions (465) Aspirin drug information
Also serious with: Dichlorphenamide Influenza Virus Vaccine, Live Abrocitinib Defibrotide
Aluminum Phosphate

Keep reading about Aluminum Phosphate

All Aluminum Phosphate interactions (56)
Also serious with: Hydroxychloroquine Infigratinib Cefuroxime Octreotide Injection
Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Aspirin + Activated Charcoal Asarabacca Beer Danshen Piracetam Siberian Cocklebur Wine Aconite + 234 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

Check another combination

Our instant two-drug interaction checker is almost here.

Coming soon

The instant two-drug checker is on its way.

In the meantime, browse the directory below to look up any drug and see its documented interactions.

Still have questions about this combination?

Every question gets a real answer from a licensed pharmacist — free, and usually within a day.

Ask the pharmacist
This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.