To treat ADHD, if Adderall is known to be NOT more effective with daily doses of >40mg, are there restrictions?

Are there restrictions if a physician wants to prescribe a patient with a greater daily dose than only 40mg? Or does it depend upon the individual policy of the pharmacy? For instance, I have read that some hospitals require comprehensive ECGs to be performed while the patient is on more than 40mg/day. This is so it can be determined with greater accuracy that in certain rare cases, the larger daily dose is proven more effective. But under normal circumstances, daily doses should not be prescribed more than what is therapeutically effective, which is known to be not greater than 40mg.