HEARTGARD® Plus (ivermectin/pyrantel) is well tolerated and safe in dogs 6 weeks or older with no minimum weight requirement. 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, click here for full prescribing information, call 888-637-4251 or visit Heartgard.com.