Any person who distributes or possesses with the intent to distribute unfinished dextromethorphan who is not registered under § 510 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 321 et seq.) or otherwise authorized by the Drug Control Act (§ 54.1-3400 et seq.) to distribute or possess unfinished dextromethorphan is guilty of a Class 1 misdemeanor. This section does not apply to a common carrier that receives or possesses unfinished dextromethorphan for the purpose of distributing such unfinished dextromethorphan between persons registered under § 510 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 321 et seq.) or otherwise authorized by the Drug Control Act (§ 54.1-3400 et seq.) to distribute or possess unfinished dextromethorphan.