It is related to Benadryl, and the dose is about the same, 2–4 mg per kilogram of body weight. There is a liquid form available if you have a small dog. Benadryl has been used in some anxiety ...

Dogs also metabolize Benadryl differently, so it’s not a good idea to rely on human dosing guidelines ... for dogs depends on their weight. A small dog will need much less than a big dog ...