According to Animal Shelter, the usual chlorpheniramine dosage for dogs is 2-8 milligrams every 8-12 hours. There is no FDA-approved dosage amount for chlorpheniramine, which is commonly prescribed by veterinarians.
Dosage can vary depending on the size of the dog as well as on any underlying sicknesses of the dog. For instance, Canine Diabetes suggests that in the case of a liquid chlorphreniramine dosage, a dog weighing from one to five kilograms should receive one half to a whole teaspoon of the medicine two to three times daily. In the case of a 60 milligram tablet, dogs in the 5-10 kilograms weight class should receive one chlorphreniramine tablet two to three times daily, while three tabs should be administered to a dog over 25 kilograms.