if you havnt used wazine before,i'd use it first. wait about 14 days then use the ivermectin pour on. i administer the ivermectin on the back of their necks making sure it goes on the skin. it should not only get rid of the gapeworm,but also get rid of round worms that have hatched since you first used the wazine. if you used wazine say,within the previous 6-8 months,i'd go ahead with the ivermectin.