You could still use that syringe. Just pull up the same amount as you would with a smaller syringe. There should be marks from 1 ml to 2 ml. How much is the weight? The dosage is roughly 0.25 ml (1/4 ml) per pound once and repeat in 10 days for roundworms. To treat for all worms except tapeworms, give it for 5 consecutive days. Egg withdrawal time is 14 days from last dose.
