(a) No driver shall be on duty and possess, be under the influence of, or use, any of the following drugs or other substances:

(1) Any 21 CFR 1308.11 Schedule I substance;

(2) An amphetamine or any formulation thereof (including, but not limited, to “pep pills,” and “bennies”);

(3) A narcotic drug or any derivative thereof; or

(4) Any other substance, to a degree which renders the driver incapable of safely operating a motor vehicle.

(b) No motor carrier shall require or permit a driver to violate paragraph (a) of this section.

(c) Paragraphs (a) (2), (3), and (4) do not apply to the possession or use of a substance administered to a driver by or under the instructions of a licensed medical practitioner, as defined in § 382.107 of this subchapter, who has advised the driver that the substance will not affect the driver's ability to safely operate a motor vehicle.

(d) As used in this section, “possession” does not include possession of a substance which is manifested and transported as part of a shipment.