Best First-Line Antacid for Occasional Heartburn
For occasional heartburn or dyspepsia in adults, calcium carbonate is the best first-line antacid, dosed at 500-1000 mg as needed when symptoms occur, with aluminum/magnesium hydroxide combinations as the preferred alternative if calcium carbonate is contraindicated. 1, 2
Calcium Carbonate as First Choice
- Calcium carbonate provides rapid, effective relief of heartburn symptoms through direct neutralization of gastric acid and inhibition of pepsin. 1
- The recommended dose is 500-1000 mg (typically 1-2 chewable tablets) taken as needed when symptoms occur. 2, 3
- Calcium carbonate has faster onset of action compared to other antacids in many patients, with symptom relief beginning within 5-15 minutes. 2
- Duration of action in the esophagus (the primary site of heartburn relief) is approximately 60 minutes. 2
- Calcium carbonate is widely available over-the-counter, inexpensive, and has an established safety profile for occasional use. 1, 4
Important Caveat About "Acid Rebound"
- Historical concerns about calcium carbonate causing "acid rebound" are based on flawed assumptions—all antacids stimulate some gastric acid secretion, but the remaining buffer compensates for this effect. 4
- When used properly for occasional symptoms, calcium carbonate is efficient, safe, and does not cause clinically significant acid rebound. 4
Alternative: Aluminum/Magnesium Hydroxide Combinations
If calcium carbonate is contraindicated (hypercalcemia, renal stones, severe renal impairment), aluminum/magnesium hydroxide combinations are the preferred alternative. 1, 2
- Dose: Two tablets of a high-potency formulation (e.g., aluminum hydroxide 400 mg/magnesium hydroxide 400 mg per tablet) as needed. 2
- These combinations provide superior esophageal pH control compared to calcium carbonate, with longer duration of action (approximately 82 minutes in the esophagus). 2
- Aluminum/magnesium hydroxide has faster onset in some patients and more sustained gastric pH elevation without the theoretical acid rebound seen with calcium carbonate. 2
When Antacids Are Insufficient
- If symptoms occur more than twice weekly or require regular antacid use beyond 2 weeks, escalate to a proton pump inhibitor (PPI) rather than continuing antacids. 5, 6
- Standard-dose PPI (omeprazole 20 mg once daily, taken 30-60 minutes before breakfast) provides significantly more effective and sustained relief than antacids for frequent symptoms. 5, 6
- Antacids are appropriate for occasional, self-limited episodes but are not suitable for chronic management of GERD or frequent dyspepsia. 1, 7
Contraindications and Precautions
- Avoid calcium carbonate in patients with: hypercalcemia, history of calcium-containing kidney stones, severe chronic kidney disease (CrCl <30 mL/min), or hypophosphatemia. 1
- Avoid aluminum-containing antacids in patients with: severe chronic kidney disease due to risk of aluminum accumulation and toxicity. 1
- Avoid magnesium-containing antacids in patients with: severe renal impairment (risk of hypermagnesemia) or chronic diarrhea. 1
- All antacids can interfere with absorption of other medications—separate dosing by at least 2 hours from other oral medications, particularly tetracyclines, fluoroquinolones, iron supplements, and levothyroxine. 1
Practical Dosing Algorithm
For typical occasional heartburn: Start with calcium carbonate 500-1000 mg chewed thoroughly as needed when symptoms occur (maximum 7000 mg/day, not to exceed 2 weeks of regular use). 1, 3
If calcium carbonate contraindicated: Use aluminum/magnesium hydroxide combination (two tablets of high-potency formulation) as needed. 2
If symptoms persist >30 minutes after antacid: May repeat one additional dose. 3
If requiring antacids >2 times per week or for >2 weeks: Transition to PPI therapy (omeprazole 20 mg once daily before breakfast). 5, 6