Section 201.21 - Declaration of presence of phenylalanine as a component of aspartame in over-the-counter and prescription drugs for human use(a) Aspartame is the methylester of a dipeptide composed of two amino acids, phenylalanine and aspartic acid. When these two amino acids are so combined to form aspartame (1-methyl N-L-[ALPHA]-aspartyl-L-phenylalanine), they produce an intensely sweet-tasting substance, approximately 180 times as sweet as sucrose. The Food and Drug Administration has determined that aspartame when used at a level no higher than reasonably required to perform its intended technical function is safe for use as an inactive ingredient in human drug products, provided persons with phenylketonuria, who must restrict carefully their phenylalanine intake, are alerted to the presence of phenylalanine in the drug product and the amount of the ingredient in each dosage unit.(b) The label and labeling of all over-the-counter human drug products containing aspartame as an inactive ingredient shall bear a statement to the following effect: Phenylketonurics: Contains Phenylalanine (_)mg Per (Dosage Unit).(c) The package labeling and other labeling providing professional use information concerning prescription drugs for human use containing aspartame as an inactive ingredient shall bear a statement to the following effect under the "Precautions" section of the labeling, as required in § 201.57(f)(2) : Phenylketonurics: Contains Phenylalanine (_)mg Per (Dosage Unit).(d) Holders of approved new drug applications who reformulate their drug products under the provisions of this section shall submit supplements under § 314.70 of this chapter to provide for the new composition and the labeling changes.52 FR 2111, Jan. 20, 1987; 52 FR 12152, Apr. 15, 1987; 53 FR 4135, Feb. 12, 1988 Approved by the Office of Management and Budget under control number 0910-0242