Standard dose: 1 mg per pound, every 8-12 hours
Disclaimer: Always consult your veterinarian before medicating your cat.
Diphenhydramine (Benadryl) can be used in cats for allergic reactions, motion sickness, and mild sedation. Veterinary dose: 1 mg per pound (2-4 mg/kg) orally every 8-12 hours. Most cats weigh 8-12 lbs, so the typical dose is 8-12 mg. Use plain diphenhydramine only — no combination products with decongestants or pain relievers. Liquid children's Benadryl (12.5 mg/5 mL) is easier to dose for cats than tablets. Side effects include sedation, dry mouth, and urinary retention. Cats may drool excessively if the medication tastes bitter. Never use time-release capsules. Always get vet approval before administering, especially for cats with heart disease, glaucoma, or urinary problems.