Spanky I use the Strongid till about 4 weeks old. Then take about 5 cc of ivermectin and squirt in about 50 cc of strongid and shake well.I then give mixture at a rate of 1cc/5 pounds. I told an old vet what I was doing and he said you are doing just right as he does the same thing. I have never used the Synanthic how would you give it?