One day is too many days to have diarrhea. Having Imodium (Loperamide) on hand to relieve your symptoms can be a life-saver. Zantac 75 (ranitidine) is an effective and inexpensive medicine for hearburn with few side effects, but may interfere with other drugs. Zantac for Dogs and Cats Zantac may be used in dogs and cats to prevent and treat stomach and intestinal ulcers as well as gastritis and acid reflux. You should talk to your veterinarian before. While the Zantac dosage for dogs will depend on the individual, the general guideline will be somewhere between 0.25 and 1 mg of ranitidine per every pound of the animal to be taken every 8 to 12 hours. Zantac tablets come in dosages of 75 mg, 150 mg and 300 mg, with injections differing according to their solution. It does help diarrhea though and won't hurt you if you use it correctly. You could ask your doc for some clonidine. That is about the only thing I ever tell anyone to do for WDs that is safe and not habit forming. Zantac is a histamine used to prevent and treat stomach ulcers and intestinal ulcers in cats and dogs. Come to petMD for a complete list of pet medications and prescriptions. Zantac belongs to a group of drugs called histamine-2 blockers. Ranitidine works by reducing the amount of acid your stomach produces. Zantac is used to treat and prevent ulcers in the stomach and intestines. Ranitidine is perhaps best known as the brand name formulated drug called Zantac. Zantac is a human formulation of the medicine (no veterinary medicine-specific versions exist), and vets oftentimes prescribe Zantac to dogs as an extra label drug. This medicine functions by inhibiting the reception of the histamine known as H-2. H-2 is responsible for signaling to the stomach lining that it. How Zantac Is Used for Dogs. Zantac is actually the commercial name for a drug called Ranitidine. Ranitidine belongs to a group of drugs known as H2 receptor antagonists. The drug ranitidine, better known under its marketed name “Zantac”, is a H2 histamine blocker commonly used to treat stomach upset, acid reflux, heartburn and peptic ulcers in dogs, the reduction in stomach acid allowing gastric ulcers time to heal. Summary. Diarrhea is found among people who take Zantac, especially for people who are female, 60+ old , have been taking the drug for 1 month, also take medication Prilosec, and have High blood pressure.