One syringe will deworm a 1,100 lb horse. Safe-Guard (fenbendazole) 10% is administered orally at a rate of 2.3 mg/lb (5 mg/kg) for the control of large strongyles, small strongyles, and pinworms. For foals and weanlings (less than 18 mos of age) where ascarias are a common problem, the recommended dose is 4.6 mg/lb (10 mg/kg); one syringe will deworm a 550 lb horse. For control of 4th stage larvae of strongylus vulgaris, the recommended dose is 4.6mg/lb daily for 5 consecutive days; administer 1 syringe for each 550 lbs body weight per day.