Side effects include low blood pressure, high blood pressure, rapid heart rate, constipation, dry mouth, and blue-green urine. Doxepin should not be used in animals with known hypersensitivity or allergy to the drug, glaucoma or problems associated with urinary retention. Use with caution in seizure-prone animals.
Notify your veterinarian of other medications that your pet is taking. Drug interactions occur with monoamine oxidase inhibitors, thyroid medications, atropine sedatives, antihistamines, norepinephrine and phenytoin. The following drugs may increase the effects of doxepin: cimetidine (Tagamet) estrogens fluoxetine (Prozac) some sedatives enalapril verapamil and ranitidine (Zantac).