Can You Take A Zpack (Azithromycin) With Antacids?

In our latest question and answer, our pharmacist discusses whether or not antacids can be taken with azithromycin.


I take TUMS and Maalox every once in awhile to deal with heartburn. Is it okay to take with a Zpack (azithromycin) I was just prescribed?

Asked by Lye On Apr 19, 2023

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Apr 19, 2023
Last updated Jul 18, 2024

Key points

  • Antacids containing magnesium or aluminum can decrease the absorption of azithromycin, but the impact of this on the effectiveness of the drug is uncertain. Nevertheless, it is generally recommended not to take azithromycin with antacids.
  • To avoid the interaction, it's recommended to separate the doses of azithromycin and antacids by at least two hours.
  • PPIs (proton pump inhibitors), such as Prilosec, do not interfere with the absorption of azithromycin.


When it comes to taking a Zpack (azithromycin) with antacids, there is a potential concern to consider.

Certain antacids, specifically those containing magnesium or aluminum, can decrease the absorption of azithromycin. This could theoretically make the antibiotic less effective.

What Do The Studies Say?

A clinical trial involving 10 participants observed that administering azithromycin immediately after a single oral dose of aluminum hydroxide/magnesium hydroxide (1,350/1,200 mg), two different types of antacid, reduced the maximum amount of azithromycin in the bloodstream (Cmax) by 24%. The following chart was published with the study:

Azith Over Time w Antacid Chart

However, antacids did not have any effect on the time it took to reach the maximum concentration or on the overall exposure of the drug in the body over time, also known as the area under the curve (AUC), which is a common measure used in pharmacology.

Pharmacist Analysis

The importance of the findings I mentioned in the above section is uncertain.

While we can expect certain antiacids (those containing magnesium or aluminum) to lower the maximum concentration of azithromycin if taken together, the impact of this isn't known as the effectiveness of azithromycin is generally thought to be based on its AUC, which appears to be unchanged with antacids, rather than maximum concentrations (Cmax).

Nevertheless, the 'Patient Counseling Information' section provided with azithromycin prescriptions does caution not to take azithromycin and aluminum- or magnesium-containing antacids simultaneously. It would be prudent to follow this precaution just to be safe.

How To Manage The Interaction

To avoid this interaction, it's recommended to separate doses of azithromycin and antacids by at least two hours.

In other words, take azithromycin at least two hours before an antacid, or two hours after, to avoid the interaction.

This would allow the body time to fully absorb azithromycin before the antacid enters the stomach, or allow time for an antacid to be completely cleared before taking azithromycin.

Additional Points

It's important to mention that proton pump inhibitors (PPIs), like Prilosec and Nexium, a type of medication commonly used for acid reflux, do not interfere with the absorption of azithromycin.

Therefore, if you are taking a PPI, there is no need to worry about potential interaction.

Additionally, although the drug information for azithromycin only lists antacids containing magnesium and aluminum as being a problem with azithromycin, most drug resources also list calcium carbonate as an antacid of concern. To be safe, it would be prudent to avoid co-administration of all calcium, aluminum, and magnesium-containing antacids.

As always, it's important to speak with your healthcare provider about any questions or concerns regarding your medication regimen.

Final Words

Thanks so much for contacting us and please feel free to do so again anytime!


  • Impact of pharmacodynamics on dosing of macrolides, azalides, and ketolides, PubMed
  • The effects of an antacid or cimetidine on the serum concentrations of azithromycin, PubMed
  • Azithromycin Prescribing Information, Pfizer

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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