12 doses of monthly heartworm prevention for dogs 25 pounds and under. I am not responsible for any reactions, please research before buying. Let me know if you have any questions, thanks! :) *HEARTGARD Plus is well tolerated. All dogs should be tested for heartworm infection before starting a preventive program. Following the use of HEARTGARD Plus, digestive and neurological side effects have rarely been reported. For more information, contact your veterinarian.