Question 1

What are H2 blockers used for?

Accepted Answer

H2 receptor antagonists (H2 blockers) reduce stomach acid production and are used to treat heartburn, GERD, peptic ulcer disease, and gastritis. Famotidine (Pepcid, Pepcid AC) is the most widely used H2 blocker, available both over the counter and by prescription. While largely supplanted by proton pump inhibitors (PPIs) for severe acid conditions, H2 blockers remain useful for milder symptoms and are preferred by some patients for their faster onset in some contexts.

Question 2

How do H2 blockers reduce stomach acid?

Accepted Answer

H2 blockers competitively antagonize histamine at H2 receptors on gastric parietal cells. Histamine is one of the main stimulants of acid secretion; blocking it reduces basal acid output by 70–80%. Unlike PPIs, which block the final step in acid production, H2 blockers do not achieve as complete acid suppression but act faster (within 1 hour) — which is why they are effective for on-demand heartburn relief. Tolerance to H2 blockers can develop within 1–2 weeks of continuous use.

Question 3

What are the side effects of H2 blockers?

Accepted Answer

H2 blockers are generally well tolerated with minimal side effects. Headache, dizziness, and fatigue are occasionally reported. Famotidine is preferred over older agents (ranitidine, nizatidine) — ranitidine (Zantac) was recalled from the market in 2020 due to contamination with NDMA, a probable carcinogen. High-dose or long-term H2 blocker use may contribute to vitamin B12 malabsorption over time.

Question 4

Should I take an H2 blocker or a PPI for acid reflux?

Accepted Answer

For infrequent heartburn, an H2 blocker taken before meals or as needed is often sufficient and appropriate. For frequent or severe GERD, erosive esophagitis, or ulcers, PPIs provide stronger, more sustained acid suppression and are generally preferred. H2 blockers are also an option for patients who prefer to avoid long-term PPI use. The best choice depends on the severity and frequency of your symptoms — consult your healthcare provider to find the most appropriate treatment.

H2 Receptor Antagonists

Overview

How do h2 receptor antagonists work?

Drugs in this class

Frequently asked questions