Sections 2-322 through 2-326 of this title shall not apply to the sale or transfer of a nonnarcotic product that includes a precursor substance defined in Section 2-322 of this title, if the product may be sold lawfully with a prescription or over the counter without a prescription pursuant to the Federal Food, Drug and Cosmetic Act, 21 U.S.C. Section 301 et seq., or a rule adopted pursuant thereto. Further, this act shall not apply to common carriers in the transaction of business as common carriers. This section shall not create an exemption for any person who has knowledge that a product sold over the counter is intended to be used to manufacture amphetamine or methamphetamine.