Pepcid (famotidine) is generally safe for dogs when given at the correct dose, and veterinarians commonly prescribe it to manage stomach acid problems. It’s one of the more frequently used over-the-counter human medications that crosses over into veterinary medicine. That said, the dose, your dog’s health history, and the specific formulation all matter.
What Pepcid Does for Dogs
Famotidine, the active ingredient in Pepcid, is an H2 blocker. It works by reducing the amount of acid the stomach produces. In dogs, vets typically use it to treat or prevent stomach ulcers, acid reflux, gastritis (inflammation of the stomach lining), and nausea caused by excess stomach acid. It’s also sometimes given alongside medications that irritate the stomach, like certain anti-inflammatory drugs, to protect the digestive tract.
The medication is short-acting and should stop working within about 24 hours in a healthy dog. Dogs with liver or kidney disease may process it more slowly, which means the effects can linger longer than expected.
Typical Dosing for Dogs
The standard veterinary dose is 0.5 to 1 mg per kilogram of body weight, given once daily by mouth. To put that in more practical terms, that’s roughly 0.25 to 0.5 mg per pound. A 20-pound dog, for example, would typically get 5 to 10 mg, while a 60-pound dog might receive 15 to 30 mg. Standard Pepcid AC tablets come in 10 mg and 20 mg sizes, which makes splitting doses fairly straightforward for medium and larger dogs.
One important detail: use only original Pepcid AC (famotidine alone). Pepcid Complete contains additional active ingredients, calcium carbonate and magnesium hydroxide, that change the safety profile and aren’t appropriate for dogs without veterinary guidance. Always check the label to make sure you’re giving the plain formulation.
Which Dogs Should Avoid It
Famotidine requires extra caution, or may not be appropriate at all, for certain dogs. Specifically, it should be used carefully in dogs that are geriatric, have liver disease, kidney disease, or heart disease, or are pregnant or nursing. Dogs with liver or kidney problems process the drug more slowly, so the medication can build up to higher-than-intended levels in their system. If your dog falls into any of these categories, the dose may need to be adjusted or an alternative treatment chosen.
Dogs with a known allergy to famotidine should not take it at all, though true allergic reactions to this drug are uncommon.
Side Effects to Watch For
Famotidine has a wide safety margin in dogs, meaning the gap between a therapeutic dose and a harmful one is relatively large. Most dogs tolerate it well, and side effects are infrequent at standard doses. When they do occur, the most commonly reported issues are mild: decreased appetite, drowsiness, or digestive changes like diarrhea or constipation.
More serious reactions are rare but can include vomiting, rapid heart rate, or restlessness. If your dog shows any unusual behavior after taking Pepcid, stopping the medication is a reasonable first step. Because the drug clears the system within about 24 hours in healthy dogs, mild side effects typically resolve quickly on their own.
Drug Interactions
Because famotidine reduces stomach acid, it can interfere with any medication that needs an acidic stomach environment to be absorbed properly. Antifungal medications are a common example. If your dog takes other medications, it’s worth confirming there’s no interaction before adding famotidine to the mix. This is especially relevant for dogs on multiple long-term prescriptions, where timing doses apart from each other can sometimes solve the problem.
Giving Pepcid at Home Safely
Famotidine can be given with or without food, though giving it on an empty stomach about 15 to 30 minutes before a meal may be most effective for dogs with acid reflux, since it gives the drug time to start suppressing acid production before food triggers more of it.
If you’re using Pepcid for a one-off stomach upset (your dog ate something they shouldn’t have, or they seem nauseated), a single dose at the lower end of the range, 0.25 mg per pound, is a reasonable short-term option. For anything beyond a day or two of use, or for recurring stomach issues, your vet should be involved. Chronic vomiting or stomach problems can signal conditions that acid reduction alone won’t fix, and masking symptoms with Pepcid could delay a diagnosis.
If you accidentally give too much, watch for signs like rapid breathing, elevated heart rate, or significant lethargy. Famotidine overdoses in dogs are rarely life-threatening, but large overdoses still warrant a call to your vet or an animal poison control hotline to assess whether intervention is needed.