Oxibendazole 22.7% (Pfizer) Effective against large & small strongyles, large round worms, pinworms, & threadworms. Wormer is NOT effective against bots. For horses of any age including foals and pregnant mares. 24 gm syringe treats up to 1,200 lbs body wt (800 lb if targeted against intestinal strongyles). Horses maintained on premises where reinfection is likely to occur should retreat in 6-8 weeks.