Section 201(p) of the Federal Food, Drug, and Cosmetic Act defines a new drug as one not generally recognised, among qualified experts, as safe and effective for the uses in its labeling. Section 505(a) prohibits introducing a new drug into interstate commerce without an approved application, and section 301(d) makes doing so a prohibited act.
An approval covers a specific product from a specific applicant. A substance that is the active ingredient of an approved medicine is still an unapproved new drug when sold by anyone else for use in people.
See also
For in vitro laboratory research only. Not for human or veterinary use. This library describes chemistry, analytical methods and published laboratory research; it gives no guidance on use in people or animals.