Honestly, this question cannot be answered without knowing more specifications about the medication and your pets. For example, what is the concentration of the amprolium (Cortid)? is this exact weight or "guesstimated"? Cortid is a dangerous drug which can lead to degenerative encephalomyelopathy if given improperly. I would suggest using a safer medication like ponazuril at a dosage of 0.1mL/lb.