Famotidine is a stomach-acid reducer that is sometimes used “off label” in dogs. “Off label” means the medication is not approved by the FDA for use in dogs, but veterinarians may prescribe it. Famotidine is available as an injectable that can be administered at a veterinary hospital and an oral form that is available over the counter (OTC).
The best-known brand name is Pepcid-AC. There are also generic equivalents. Famotidine can be used in cases of stomach ulcers, esophagitis, gastritis, reflux disorders, disorders that result in hypersecretion of stomach acid (gastrinoma, systemic mastocytosis), and stomach issues related to kidney disease. However, you should have a diagnosis from your veterinarian before using this medication.
Famotidine Is Not an Antacid
Technically, famotidine is an H2 receptor antagonist that competitively inhibits histamine-induced gastric acid secretion from the stomach parietal cells. Antacids reduce existing stomach acids, while medications like famotidine reduce the amount of acid produced by the stomach. In general, this drug class has a good safety profile, and adverse effects are uncommon if therapeutic doses are administered.
Famotidine should not be used in dogs with a known hypersensitivity to it or other H2 receptor agonists. It should be used with caution in dogs with diminished kidney or liver function or heart disease. Dogs taking an anticoagulant should have prothrombin times monitored. Famotidine can also affect the absorption of other medications because it alters the normal acidity of the stomach.
Famotidine is 42 times more potent than cimetidine (brand name Tagamet) in reducing stomach acid secretion. Compared to omeprazole (brand name Prilosec), famotidine has a weaker effect in dogs. Given chronically over time, tolerance is known to develop, making famotidine less effective for prolonged therapy. If given twice daily, stomach acidity regresses to the untreated state by day 14.
After administration, peak concentration of famotidine in the blood is achieved within two hours. It does cross the placenta and distributes to the milk in nursing females. Famotidine is cleared out of the system via the kidneys.
Famotidine Dosage for Dogs
The recommended dosage is 0.5 to 1 milligram (mg) per kilogram (kg) of body weight—or about 0.25 to 0.5 mg per pound of body weight. It can be given by mouth or by injection every 24 hours. If given orally, it’s best given 30 minutes prior to a meal.
The over-the-counter version of famotidine come in 10 mg and 20 mg tablets. Be sure the famotidine you get for your dog contains no other active ingredients and that you administer accurate dosages, under the guidance of your veterinarian.
Overdosage via intravenous administration can result in vomiting, increased heart rate, and hypersalivation. Chronic overdosage via oral administration can result in mild weight loss. Overall, H2 antagonists have fairly wide margins of safety.
If you have a dog who you think would benefit from treatment with famotidine, please check with your veterinarian before administering it. If your dog is on other medications, they might be less effective due to the altered acidity of the stomach. Also, a dog who is not eating or vomiting might have a problem that cannot be solved with famotidine alone.
Oral Famotidine Dosage Chart for Dogs
Recommended dosage can be given every 24 hours by mouth.
| Body Weight (lbs.) | Famotidine Dosage |
|---|---|
| 5 -10 | 2.5 mg |
| 11 - 21 | 5 mg |
| 22 - 44 | 10 mg |
| 45 - 66 | 15 mg |
| 67 -88 | 20 mg |
| 89 - 132 | 30 mg |
| 133 - 176 | 40 mg |
