S-Adenosylmethionine. Denosyl has been shown to increase hepatic glutathione levels in cats and dogs. Glutathione is a potent antioxidant that protects liver cells from toxins and death. Denosyl is recommended to improve hepatic glutathione levels in compromised animals to help maintain and protect liver function. The tablets should be given on an empty stomach at least one hour before feeding. The usual dose in cats and dogs is based on weight. For pets 13 to 34 pounds give 1 tablet.