Gastroenterology · USMLE Step 1 and Step 2

Antacids song

Antacids - Mechanism & Side Effects, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Antacids

Full song on YouTube ↗Spotify ↗

Key points in this song10

Calcium carbonate neutralizes gastric acid and provides the fastest onset of action among antacids, but causes acid rebound and constipation with chronic use.
Magnesium hydroxide acts as an osmotic laxative and can cause hypermagnesemia in patients with renal failure, making it contraindicated in CKD.
Aluminum hydroxide binds phosphate in the gut, making it the antacid of choice for managing hyperphosphatemia in chronic kidney disease; chronic use causes constipation and hypophosphatemia.
Sodium bicarbonate provides rapid but short-lived neutralization; systemic absorption can cause metabolic alkalosis and fluid retention, making it unsafe in hypertension and heart failure.
Calcium carbonate is a significant source of dietary calcium supplementation but can cause milk-alkali syndrome with excessive use: hypercalcemia, metabolic alkalosis, and renal insufficiency.
Antacids impair absorption of fluoroquinolones, tetracyclines, and iron by forming insoluble chelation complexes; these drugs should be separated by at least 2 hours.
Antacids reduce the bioavailability of ketoconazole and itraconazole, which require an acidic environment for absorption.
Unlike PPIs and H2 blockers, antacids do not reduce acid secretion; they raise gastric pH by direct chemical neutralization, providing symptomatic relief but not mucosal healing.
The combination of aluminum and magnesium hydroxide (e.g., Maalox, Mylanta) balances constipation and diarrhea side effects and is commonly used for GERD and peptic ulcer symptom relief.
Antacids can falsely elevate urinary pH on dipstick testing and interfere with interpretation of urine electrolytes in acid-base workups.