Buckman Co. v. Plaintiffs' Legal Comm., 531 U.S. 341 (U.S.S.Ct. 2001) ("the FDCA expressly states in part that '[n]othing in this chapter shall be construed to limit or interfere with the authority of a health care practitioner to prescribe or administer any legally marketed device to a patient for any condition or disease within a legitimate health care practitioner-patient relationship.' 21 U.S.C. § 396 (1994 ed., Supp. IV).").