H2 Blockers (Famotidine)
Older but useful acid-reducing medications — work faster than PPIs and good for as-needed use, mild reflux, or as a second-line addition to PPIs at night.
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
Drug class
Histamine-2 receptor antagonists (H2 blockers)
Examples
Famotidine (Pepcid, Famodine) is the only one widely available now after ranitidine was withdrawn globally for impurity concerns. Cimetidine is rarely used due to drug interactions.
How it works
H2 blockers reduce stomach acid by blocking histamine — one of three signals that tell the stomach to produce acid. They are weaker than PPIs (which block the acid pump itself) but work faster (within 30-60 minutes) and last 6-12 hours. After several weeks of daily use, the body adapts (tachyphylaxis) and effect weakens.
What it treats
- Mild GERD or occasional heartburn
- Nighttime acid breakthrough on PPI (added at bedtime)
- Stress ulcer prophylaxis in some hospital settings
- Can be taken as-needed before known trigger meals
How to take it
Famotidine 20-40 mg, up to twice daily. Can take with or without food (no fasting required, unlike PPIs). Onset 30-60 minutes; lasts 6-12 hours. For nighttime symptoms: take 30 minutes before evening meal. Available over-the-counter at lower strengths (10-20 mg) and prescription at higher strengths.
Common side effects
- Headache (rare and mild)
- Constipation or diarrhea (rare)
- Dizziness (rare)
- Generally very well tolerated
Serious side effects — call your doctor
Confusion or hallucinations, especially in elderly with kidney disease
Stop the medication and see your doctor — needs dose adjustment.
Severe allergic reaction (rash, swelling, breathing difficulty)
Emergency.
Interactions
Few significant interactions. Famotidine has fewer interactions than older H2 blockers. May reduce absorption of certain medications (ketoconazole, atazanavir) — separate by 2 hours.
Monitoring
No routine monitoring needed for short-term use. Long-term: occasional check of vitamin B12 in elderly, kidney function adjustment.
Pregnancy & breastfeeding
Famotidine is considered safe in pregnancy and breastfeeding. Often used when antacids alone don't control reflux.
In the Saudi context
Famotidine is widely available over-the-counter in Saudi pharmacies at low cost. Higher strengths (40 mg) require prescription. Often used during Ramadan for nighttime reflux.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Should I take this with my PPI or instead of it?
- Is famotidine safe long-term?
Medically reviewed by: SGA Patient Education Panel · Last reviewed 24/04/2026