Antacids are generally the first line of defence against GERD and acid reflux, and are the first drugs recommended by a doctor. Most antacids are over-the-counter medications that use a combination of calcium, aluminum, and magnesium salts to neutralize stomach acids.
Over-the-counter antacids, while generally quite mild, do have some side effects to be aware of.
Antacids that contain magnesium salts can cause diarrhea, while antacids with aluminum salts can cause constipation. Often, manufactures attempt to "balance" these effects out by adding both types of salts to an antacid formulation. Calcium salts can also cause constipation in some people. Calcium-based OTC antacids can be a good source of supplementary calcium.
People with kidney disease should consult their doctor before using any OTC antacids containing magnesium, calcium, or aluminum salts.
H2 blockers are histamine-blockers, and work by inhibiting the effects of histamine, which is a pro-inflammatory molecule that stimulates stomach acid production. Mild H2 blockers can be bought over-the-counter, but stronger, more effective preparations are prescription-only. The following medications are some commonly-prescribed H2 blockers.
These medications can cause side effects such as headaches, dizziness, gas, diarrhea, sore throat, and runny nose. In men, these medications can cause lose of libido or impotence.
Older H2 blockers, such as cimetidine, can interfere with metabolism of many other drugs, including blood thinners, and certain types of antidepressants.
Proton Pump Inhibitors
These prescription-only medications also reduce the production of stomach acid. Often these medications are prescribed for people who have not responded to H2 blockers. For most people, proton pump inhibitors are more effective at blocking acid production, and last for a longer duration, than H2 blockers. Examples of PPI medications include:
Side effects of proton pump inhibitors include headaches, abdominal pain, nausea, bloating, gas, constipation, and diarrhea.
Long-term use can cause vitamin B12 deficiency. In addition, there are indications that long-term use might increase bone fragility in older people.
Also called pro-motility agents, these medications help strengthen the lower esophageal sphincter, the ring of muscle that, in people with GERD, does not function at an optimal level. In addition, prokinetics help the stomach empty faster, reducing the risk that stomach contents might be regurgitated.
Most prokinetics work by binding dopamine receptors and acting as receptor agonists, thus preventing dopamine from inhibiting the release of acetylcholine. This in turn increases the available concentration of acetylecholine, which increases gastrointestinal peristalsis.
The side effects of prokinetic medications can be serious, and these medications are therefore not prescribed often. Serious potential side effects of prokinetics include hypertension, hypotension, depression, tachycardia, and a movement disorder called tardive dyskinesia. These side effects become increasingly common with long-term prokinetic use.
These medications can worsen the effects of Parkinson’s disease due to their activity on dopamine receptors, and cannot be used by people with this disease.
In addition, long-term use of prokinetic medications can worsen symptoms in people with clinical depression.
Consumer Reports at Health.org: Proton Pump Inhibitors (PDF)
National Institute of Diabetes and Digestive and Kidney Diseases at the National Digestive Diseases Information Clearing House: Heartburn, Gastroesophageal Reflux (GER), and Gastroesophageal Reflux Disease (GERD)