Clinically significant drug interactions with antacids: an update.

Area of Science:

• Pharmacology
• Drug Interactions
• Gastroenterology

Background:

• Antacids are increasingly used as over-the-counter (OTC) medications.
• Despite the availability of H2RAs and PPIs, antacids remain relevant for managing gastric acidity.
• Antacids can influence the absorption of other drugs through various mechanisms.

Purpose of the Study:

• To review the mechanisms and clinical relevance of drug-drug interactions (DDIs) involving antacids.
• To highlight specific drug classes susceptible to antacid-related DDIs.
• To discuss the implications of new combination OTC formulations.

Main Methods:

• Literature review of clinical studies and prescription information.
• Analysis of antacid formulation components and their chemical properties.
• Evaluation of pharmacokinetic alterations caused by antacids.

Main Results:

• Polyvalent cations in antacids can form insoluble complexes, reducing bioavailability of drugs like tetracyclines and fluoroquinolones.
• Antacids can alter drug absorption by changing gastric pH, though generally to a lesser extent than H2RAs or PPIs.
• Specific drugs, including bisphosphonates, molecular-targeting agents (e.g., tyrosine kinase inhibitors), and eltrombopag, may be affected by antacids.

Conclusions:

• Antacid-drug interactions remain clinically relevant, particularly with OTC use and specific drug classes.
• Understanding DDIs with antacids is crucial for safe medication use, especially for antibiotics and bisphosphonates.
• Combination antacid-H2RA products pose an increased risk of DDIs through combined mechanisms.