Zimecterin Paste horse dewormer from Merial contains 1.87% invermectin. For use in horses of all ages, including mares at any stage of pregnancy, for the removal and control of large strongyles, small strongyles, pinworms, ascarids, hairworms, stomach worms, bots, lungworms and threadworms. Zimectrin Paste kills 60 species and stages of parasites! Each syringe treats up to 1,250 lbs body weight. 100% satisfaction guaranteed.