There are only three classes of medications for GERD. PPIs, H2 blockers, and Antacids.
Antacids
Of the three classes, antacids are the fastest acting. They start providing relief to the patient within five minutes. As such, should be used as needed (on-demand) for breakthrough symptoms that occur ideally less than once per week. They don’t prevent GERD. They simply neutralize stomach pH decreasing the exposure of the esophageal mucosa to acid from the stomach during episodes of reflux. Antacids only work for 30 to 60 minutes and may cause side effects like constipation or diarrhea depending on which antacid you use.
| Antacids | H2 Blockers | PPIs | |
| Onset of action (how soon they start working) | Within 5 minutes | Within 1hr | Can take up to 4 days to take effect |
| Duration of action (how long they last) | 30 to 60 minutes | Lasts about 9-12 hrs | Last 24 hrs up to 3 days. |
| End Result of Action | Neutralizes acid in stomach | suppress gastric acid secretion | suppress gastric acid secretion |
| Mechanism of action (how they work) | block, histamine, one of the first stimuli for acid production. | Block the proton pump that pumps protons (H+) into the stomach in exchange for potassium. H+ is acid. | |
| Where they work | In stomach lumen | Inside parietal cells*. “H2 blockers work by blocking the histamine receptors in parietal cells to decrease the amount of acid produced (although there are other stimuli so that some acid is still produced).” |
Inside parietal cells PPIs work by “shutting down the proton pumps in these cells and preventing the acid from being secreted into the stomach.” |
| Efficacy (How well they work) | PPIs yield greater acid suppression than H2 blockers. This is due to the fact that other stimuli, in addition to histamine 2, stimulate acid production in the stomach and H2-blockers only block histamine 2. | ||
| Side effects | |||
| Common dosages | Ranitidine 150 mg PO BID | Pantoprazole 20mg po daily. NB: Can be taken twice daily. |
*Parietal cells are acid-producing cells in the lining of the stomach.
PPIs and H2 blockers work at different stages of acid production.
“How they work: They work at different stages in the production of stomach acid. H2 blockers (histamine blockers) block one of the first stimuli for acid production. PPIs block the final step in the pathway of acid secretion in the stomach. In other words, the acid which has been produced (which may be reduced due to an H2 blocker) is prevented from arriving in the stomach.”
https://www.verywell.com/how-are-ppis-different-from-h2-blockers-1742292
Pharmacology of Proton Pump Inhibitors: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2855237/