Antacids, Mechanism of Action, Side effects, contraindications, Brand Generic Drugs, Pregnancy
Table of Contents
Antacids
Antacids are medications that help neutralize stomach acid to relieve symptoms caused by excess acid production, such as heartburn, indigestion, and acid reflux.
Why Do People Take Antacids?
People take antacids to alleviate discomfort caused by:- Heartburn – A burning sensation in the chest due to stomach acid flowing back into the esophagus (acid reflux).
- Indigestion (Dyspepsia) – Discomfort or pain in the upper abdomen, often after eating.
- Acid Reflux (GERD) – Frequent heartburn due to chronic backflow of stomach acid.
- Stomach Ulcers – Antacids may provide temporary relief, though they don’t heal ulcers (other medications like PPIs or H2 blockers are more effective).
Antacids Onset of Action
- Onset of Action: Fast (within minutes)
- Duration: Short (20–60 minutes on an empty stomach; up to 3 hours if taken with food)
Antacids Mechanism of Action
- Neutralize hydrochloric acid (HCl) in the stomach → raise gastric pH.
- Do not reduce acid production (unlike H2RAs or PPIs).
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Common Antacids Available
| Generic Name | Brand Name(s) | Common Side Effects |
| Calcium carbonate | Tums, Rolaids (dual formula) | Constipation, gas, bloating, hypercalcemia |
| Magnesium hydroxide | Milk of Magnesia | Diarrhea, hypermagnesemia (especially in renal disease) |
| Aluminum hydroxide | Amphojel (less common), Maalox, Mylanta | Constipation, hypophosphatemia, aluminum toxicity |
| Sodium bicarbonate | Alka-Seltzer | Gas, bloating, metabolic alkalosis, sodium overload |
| Magnesium hydroxide + Aluminum hydroxide | Maalox, Mylanta | Balanced bowel effects, diarrhea (from Mg), constipation |
| Calcium carbonate + Magnesium hydroxide | Rolaids | Constipation or diarrhea, gas, hypercalcemia |
| Magnesium hydroxide + Aluminum hydroxide + Simethicone | Gelusil | Gas relief, balanced bowel effects, nausea |
| Aluminum hydroxide + Magnesium carbonate + Alginic acid | Gaviscon | Foam barrier for reflux, bloating, nausea |
- Calcium, Aluminum causes Constipation, Magnesium causes Diahhrea.
- Hypercalcemia: A condition where there is too much calcium in the blood
- Hypermagnesemia: A condition of elevated magnesium levels in the blood
- Metabolic Alkalosis: A condition where the blood becomes too alkaline due to
- Hypophosphatemia: Low phosphate levels in the blood
Antacids long term use complications
1. Masking Serious Conditions
Gastrointestinal cancers or peptic ulcers may go undiagnosed if symptoms are suppressed by antacids.
2. Rebound Acid Hypersecretion
Especially with calcium-containing antacids, stopping them suddenly may lead to increased acid production.
3. Altered Absorption of Nutrients & Medications
Long-term use can impair absorption of:
- Iron
- Calcium
- Magnesium
- Vitamin B12
- Certain medications like tetracyclines, fluoroquinolones, thyroid meds, and antifungals.
Antacids Drug Interactions
Antacids can interact with various medications, altering their absorption, effectiveness, or side effects. Antacids can affect medications by:
- Altering gastric pH
- Chelation with the drug (forming insoluble complexes)
- Changing GI motility
- Altering urinary pH
Common Antacids-Medication Interactions
| Medication | Effect of Antacid | Mechanism | Recommendation |
| Tetracyclines (e.g., doxycycline) | ↓ Absorption | Chelation with Al, Mg, or Ca | Separate by at least 2-4 hours |
| Fluoroquinolones (e.g., ciprofloxacin) | ↓ Absorption | Chelation with Al, Mg, or Ca | Separate by 2 hours before or 6 hours after |
| Iron supplements (ferrous sulfate) | ↓ Absorption | Increased gastric pH | Take before antacids or space 2 hours |
| Levothyroxine | ↓ Absorption | Binding and pH change | Take 4 hours apart |
| Azole antifungals (e.g., ketoconazole, itraconazole) | ↓ Absorption | Requires acidic pH for absorption | Avoid antacids within 2 hours |
| Enteric-coated drugs | Premature dissolution | Increased gastric pH | Use with caution |
| Digoxin | Altered absorption | pH and motility changes | Monitor digoxin levels |
| H2 blockers / PPIs | Additive pH effect | Synergistic acid suppression | Monitor for changes in absorption of pH-sensitive drugs |
| Sulfonylureas (e.g., glyburide) | Enhanced effect (rare) | Possible delayed absorption | Monitor blood sugar |
| Salicylates (e.g., aspirin) | ↓ Renal excretion (sodium bicarb) | Alkalinization of urine | Monitor toxicity risk |
- Aluminum & Magnesium-based: Interact most via chelation.
- Calcium carbonate: Can interfere with iron and thyroid hormones.
- Sodium bicarbonate: Alters urine pH, affects elimination of acidic/basic drugs.
Antacid use in Special Populations
Antacids are generally safe for short-term use, but certain populations (e.g., pregnant women, elderly, children, and those with kidney disease) need special considerations due to potential risks.
Antacids for Pediatrics
Use with caution and usually only under medical supervision.- Avoid magnesium hydroxide and aluminum-based antacids in infants – risk of toxicity, poor renal clearance.
- Sodium bicarbonate should be avoided due to risk of metabolic alkalosis and sodium overload.
Antacids in Pregnancy
✅ Generally Safe Options- Calcium carbonate (Tums): Category B – safe and commonly recommended.
- Magnesium hydroxide/aluminum hydroxide (Maalox, Mylanta): Generally safe for short-term use.
- Use lowest effective dose.
- Sodium bicarbonate: Avoid due to systemic alkalosis and fluid retention risk.
- Excessive calcium intake (>2500 mg/day): Risk of kidney stones and milk-alkali syndrome.
Antacids in Lactation and Breastfeeding
✅ Safe Options- Calcium carbonate, aluminum, and magnesium-containing antacids are generally safe.
- Very little passes into breast milk.
- Monitor for infant GI discomfort if high doses are used, especially magnesium (may cause diarrhea in infants).
Antacids for Geriatrics or Elderly Population (Age 65+)
✅ Use With Monitoring- Calcium carbonate and magnesium/aluminum combos are used, but monitor for:
- Constipation (aluminum, calcium)
- Diarrhea (magnesium)
- Drug interactions with some medications (common in elderly)
- Risk of electrolyte imbalance, bone demineralization, and drug malabsorption (e.g., B12, iron).
- Increased sensitivity to drug interactions due to polypharmacy.
| Population | Safest Choice | Avoid | Key Concerns |
| Pregnant Women | Calcium carbonate | Sodium bicarbonate | Fluid retention, alkalosis |
| Elderly | Calcium carbonate | Long-term Mg/Al antacids | Constipation, drug interactions |
| Children | Pediatric formulations | Sodium bicarbonate | Electrolyte imbalances |
| Kidney Disease | Calcium carbonate | Mg/Al antacids | Toxicity (Mg/Al buildup) |
| Heart Disease | Low-sodium antacids | Sodium bicarbonate | High sodium → BP/heart strain |
Natural Antacids / Antacid Substitute / Home Remedies
Natural antacids that can help relieve heartburn and indigestion symptoms. These home remedies work by either neutralizing stomach acid or soothing the digestive tract.
| Natural Antacid | How It Works | Caution |
| Baking Soda | Neutralizes stomach acid quickly | Occasional use only; high sodium, may cause alkalosis |
| Aloe Vera Juice | Soothes esophagus & stomach lining; anti-inflammatory | Use only aloin-free (non-laxative) versions |
| Ginger | Anti-inflammatory, eases nausea & indigestion | In large amounts, may cause heartburn or thin blood |
| Chamomile Tea | Calms digestive tract, reduces inflammation | May cause allergic reactions (especially in ragweed allergy sufferers) |
| Slippery Elm | Coats and soothes the stomach and esophagus | May affect absorption of medications; space out doses |
| Licorice Root (DGL) | Increases stomach mucus to protect lining | Avoid regular licorice; can raise blood pressure |
| Apple Cider Vinegar | May help balance low stomach acid (not for everyone) | May worsen reflux in some; always dilute |
| Bananas | Natural antacid effect, coats stomach | May not be effective for everyone |
| Melon (Cantaloupe) | Low-acid fruit, soothes stomach | Rarely, may trigger reflux in some individuals |
| Fennel Seeds | Aids digestion, reduces bloating & gas | Large doses may affect estrogen-sensitive conditions |
Antacid Tablets OTC
| Brand Name | Active Ingredient(s) | Type | Best For |
| Tums | Calcium carbonate | Chewable | Fast relief, calcium supplement |
| Rolaids | Calcium carbonate + Magnesium hydroxide | Chewable | Balanced relief (less constipation) |
| Maalox (Tablets) | Aluminum hydroxide + Magnesium hydroxide | Chewable | General heartburn/indigestion |
| Mylanta (Tablets) | Aluminum hydroxide + Magnesium hydroxide + Simethicone | Chewable | Heartburn + gas relief |
| Gaviscon (Tablets) | Aluminum hydroxide + Magnesium carbonate + Alginate | Chewable | Acid reflux (forms protective foam barrier) |
| Alka-Seltzer | Sodium bicarbonate + Aspirin (or NSAID-free versions) | Effervescent | Fast relief (but high sodium) |
| Pepcid Complete | Calcium carbonate + Famotidine (H2 blocker) | Chewable | Dual action (fast + long-lasting) |
| Eno (Powder/Tablets) | Sodium bicarbonate + Citric acid | Effervescent | Quick relief (high sodium) |
Frequently Asked Questions and Answers
What Are Antacids Used For?
Answer: Antacids neutralize stomach acid to relieve:- Heartburn (acid reflux)
- Indigestion (upset stomach)
- GERD symptoms (occasional acid reflux)
- Stomach ulcers (temporary relief)
How Do Antacids Work?
Answer: They contain alkaline compounds (calcium, magnesium, aluminum) that neutralize stomach acid, raising pH to reduce irritation.How Quickly Do Antacids Work?
Answer:- Liquid antacids → 1-3 minutes
- Chewable tablets → 5-15 minutes
- Effects last 30 mins to 2 hours.
Can I Take Antacids Every Day?
Answer:- Short-term: Safe for occasional use.
- Long-term: Risk of side effects (kidney stones, mineral imbalances).
- Better alternatives: PPIs (omeprazole) or H2 blockers (famotidine) for chronic issues.
What Are the Side Effects of Antacids?
Answer:- Magnesium-based → Diarrhea
- Aluminum/calcium-based → Constipation
- Sodium bicarbonate → Bloating, high blood pressure
- Long-term use → Kidney problems, nutrient deficiencies
Are Antacids Safe During Pregnancy?
Answer:- Safest: Calcium carbonate (Tums).
- Avoid: Sodium bicarbonate (Alka-Seltzer).
- Moderate use only—consult a doctor if symptoms persist.
Which Antacid Is the Strongest?
Answer:- Fastest relief: Liquid antacids (Mylanta, Maalox).
- Longest-lasting: Calcium carbonate (Tums Extra Strength).
- For severe GERD: PPIs (Nexium, Prilosec) are stronger.
Do Antacids Cause Kidney Damage?
Answer:- Rare in healthy people with short-term use.
- Risk in kidney disease: Magnesium/aluminum can build up.
- Safer choice: Calcium carbonate (monitor intake).
What Are Natural Alternatives to Antacids?
Answer:- Baking soda (1/2 tsp in water) – Quick but high sodium.
- Ginger tea – Soothes digestion.
- Aloe vera juice – Reduces inflammation.
- Apple cider vinegar (diluted) – Helps some with acid reflux.
