The backflow of stomach acid and contents into the esophagus causes heartburn and its associated symptoms. When heartburn becomes chronic, it can lead to gastroesophageal reflux disease, or GERD. Antacids are commonly used to relieve heartburn, but stronger proton pump inhibitor medication may be advised when symptoms are more than occasional. For quick relief, however, antacids work by temporarily neutralizing excess stomach acid. Magnesium, a naturally occurring mineral, is a key component in many over-the-counter antacids. While magnesium is generally safe to ingest, it is important to know how it works, what side effects might arise and when not to take it.
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Magnesium-based antacids are often effective in treating infrequent heartburn, mild GERD or acute flares of chronic GERD. Magnesium compounds are incorporated into many over-the-counter heartburn treatments, since they work by neutralizing stomach acids. They are generally built into an antacid in the form of magnesium oxide, magnesium carbonate (Mylanta), magnesium trisilicate (Gaviscon), and magnesium hydroxide (Maalox, Milk of Magnesia, Rolaids). Magnesium-based antacids also often contain other ingredients to aid in symptom relief. Antacids are most optimally used after meals and at bedtime and should not be used in excess of what is instructed on drug packaging. Antacids may also contain sodium bicarbonate, aluminum hydroxide or calcium carbonate.
Magnesium Side Effects and Contraindications
Generally, magnesium-based antacids are very safe when taken as directed. The biggest side effect is diarrhea because magnesium is not absorbed by the intestines. To counter this side effect, some medications add aluminum hydroxide to the antacid because that ingredient is constipating -- thus, countering the laxative effects of magnesium. Magnesium can also interact with certain prescription medications and medical problems, so people should be careful to look for any contraindications prior to use. Magnesium can adversely affect certain antibiotics, antivirals, diuretics and bisphosphonates. Ingested magnesium is cleared by the kidneys, so people with kidney failure on dialysis may not be able to effectively clear the extra magnesium from their bloodstream. Signs of a magnesium toxicity may include difficulty breathing, low blood pressure and slow reflexes.
Limitations of Magnesium-Based Antacids
While magnesium-based antacids offer quick relief, they can only be taken 5 to 7 times a day and are not recommended for treating chronic GERD. Some people may need additional medications and changes in their lifestyle in conjunction with magnesium-based antacids to prevent and treat symptoms of GERD. Examples of lifestyle modifications that may help frequent heartburn include losing weight, eliminating triggering foods, sleeping with extra pillows and avoiding meals 2 to 3 hours before bedtime. If someone has persistent heartburn despite lifestyle modifications and uses antacids frequently, the 2013 American College of Gastroenterology guidelines suggest adding other medications to help control and treat GERD. Proton pump inhibitors and H2 blockers are two such medications that help to suppress stomach acid.
When to Seek Medical Attention
If you are using antacids daily or frequently for more than 2 weeks, see your doctor so that you can be evaluated and treated for GERD if appropriate. If you are using magnesium-based antacids, be sure to watch for symptoms of toxicity such as diarrhea, vomiting, fatigue, shortness of breath or lethargy. Call your doctor right away if you develop chest pain, as you should ensure your symptoms are not from a cardiac issue.
Medical advisor: Jonathan E. Aviv, M.D., FACS