Gaviscon is a popular over-the-counter remedy for heartburn and acid reflux. It works by forming a protective barrier, or 'raft,' on top of the stomach contents to prevent acid from splashing up into the esophagus, and by neutralizing excess stomach acid [1.7.3, 1.7.4]. Its active ingredients often include sodium alginate along with antacids like calcium carbonate, magnesium carbonate, or aluminum hydroxide [1.2.1, 1.7.5]. While effective, these antacid components can interfere with the body's ability to absorb other medications.
The Mechanisms of Interaction: Chelation and pH Changes
The primary ways Gaviscon interacts with other drugs are through chelation and by altering stomach acidity (pH).
- Chelation: The metallic ions in Gaviscon's antacids (like calcium, magnesium, and aluminum) can bind to other drugs in the stomach. This process, called chelation, forms an insoluble complex that the body cannot absorb, rendering the other medication less effective or completely ineffective [1.5.3].
- Altered Stomach pH: Some medications require a highly acidic environment to dissolve properly before they can be absorbed into the bloodstream. By neutralizing stomach acid, Gaviscon can reduce the absorption of these pH-dependent drugs [1.2.4].
Because of these interactions, it's not about which meds you can't take, but when you take them.
Key Medications That Interact with Gaviscon
Properly timing your medication schedule is essential when using Gaviscon. The NHS recommends not taking Gaviscon within two hours (before or after) of taking many common medications [1.8.1]. For some drugs, a longer interval is necessary.
Certain Antibiotics (Tetracyclines and Quinolones)
This is one of the most critical interactions. Antacids can significantly decrease the absorption of tetracycline antibiotics (e.g., doxycycline, minocycline) and quinolone antibiotics (e.g., ciprofloxacin, levofloxacin) [1.2.1, 1.5.1]. The antacid ingredients bind to the antibiotic, which can lead to treatment failure. To avoid this, antibiotics should be taken at least 2 hours before or 4 to 6 hours after Gaviscon [1.5.3].
Thyroid Hormones (Levothyroxine)
Levothyroxine, used to treat hypothyroidism, is highly sensitive to absorption issues. The calcium, aluminum, and magnesium in antacids can bind to levothyroxine and prevent it from being absorbed properly, reducing its effectiveness [1.4.4]. It is crucial to separate doses of levothyroxine and Gaviscon by at least four hours [1.4.2, 1.4.3, 1.4.6].
Bisphosphonates
These drugs are used to treat osteoporosis (e.g., alendronate, risedronate) and already have very low absorption rates. Taking them with Gaviscon, which contains calcium and other minerals, can further reduce their absorption, making them less effective at strengthening bones [1.2.1, 1.6.1]. You should take bisphosphonates at least 30-60 minutes before any other food, drink, or medication, including Gaviscon [1.6.1, 1.6.3].
Iron Supplements
Similar to other interactions, the antacids in Gaviscon can reduce the acidity of the stomach and bind to iron, impairing its absorption [1.2.4, 1.6.5]. To ensure you get the full benefit of your iron supplement, you should take it at least two hours before or two hours after taking Gaviscon [1.6.4].
Other Affected Medications
A wide range of other drugs can be affected by Gaviscon, typically requiring a 2-hour dosing window. These include:
- Antifungals: Drugs like ketoconazole and itraconazole need stomach acid for absorption [1.2.3].
- Certain Heart Medications: Digoxin absorption may be impacted [1.2.1].
- Steroids: The absorption of oral corticosteroids can be affected [1.2.5].
- HIV medications: Drugs such as atazanavir, raltegravir, and elvitegravir can interact with antacids [1.2.2].
Gaviscon Formulation Comparison
The active ingredients in Gaviscon can vary, especially between different countries (like the US vs. the UK), which affects potential interactions. Always check the label of your specific product.
| Formulation (Example) | Common Antacid Ingredients | Main Interaction Concern |
|---|---|---|
| Gaviscon (US) | Aluminum Hydroxide, Magnesium Carbonate [1.3.5] | Aluminum and Magnesium are strong binders (chelators) of other drugs [1.5.6]. |
| Gaviscon Double Action (UK) | Calcium Carbonate, Sodium Bicarbonate [1.7.5] | Calcium can bind strongly to drugs like tetracyclines, quinolones, and levothyroxine [1.2.1]. |
| Gaviscon Advance (UK) | Potassium Bicarbonate [1.7.6] | Contains no calcium, magnesium, or aluminum, but still raises stomach pH, affecting pH-dependent drugs [1.7.5]. |
Conclusion: Safe Usage is About Timing
Gaviscon is an effective solution for reflux, but it must be used thoughtfully as part of a wider medication regimen. Its antacid components can significantly reduce the absorption and effectiveness of many critical prescription and over-the-counter drugs. The most important strategy for safe use is timing. By adhering to the 2-to-4-hour rule for spacing Gaviscon and other medications, you can generally avoid these negative interactions. However, this is a general guideline, and you should always read medication labels and, most importantly, consult with your doctor or pharmacist to create a dosing schedule that is safe and effective for your specific health needs.
For more information from an authoritative source, you may consult the UK National Health Service (NHS) page on Gaviscon.
