Section 391.41(b)(12) states: A person is physically qualified to drive a CMV if that person does not use a controlled substance identified in 21 CFR 1308.11, Schedule I, an amphetamine, a narcotic, or any other habit-forming drug.

Exception: A driver may use such a substance or drug, if the substance or drug is prescribed by a licensed medical practitioner who is familiar with the driver’s medical history and assigned duties; and has advised the driver that the prescribed substance or drug will not adversely affect the driver’s ability to safely operate a CMV. This exception does not apply to methadone.

Medical Examiners are required to give careful consideration to the effects of medications on a driver’s ability to operate a CMV safely before rendering the driver qualified.