[Code of Federal Regulations] [Title 21 Volume 5] [Revised as of April 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 21CFR320.29] [Page 188] TITLE 21--FOOD AND DRUGS CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) PART 320--BIOAVAILABILITY AND BIOEQUIVALENCE REQUIREMENTS--Table of Contents Subpart B--Procedures for Determining the Bioavailability or Bioequivalence of Drug Products Sec. 320.29 Analytical methods for an in vivo bioavailability or bioequivalence study. (a) The analytical method used in an in vivo bioavailability or bioequivalence study to measure the concentration of the active drug ingredient or therapeutic moiety, or its active metabolite(s), in body fluids or excretory products, or the method used to measure an acute pharmacological effect shall be demonstrated to be accurate and of sufficient sensitivity to measure, with appropriate precision, the actual concentration of the active drug ingredient or therapeutic moiety, or its active metabolite(s), achieved in the body. (b) When the analytical method is not sensitive enough to measure accurately the concentration of the active drug ingredient or therapeutic moiety, or its active metabolite(s), in body fluids or excretory products produced by a single dose of the test product, two or more single doses may be given together to produce higher concentration if the requirements of Sec. 320.31 are met. [42 FR 1648, Jan. 7, 1977, as amended at 67 FR 77674, Dec. 19, 2002] [[Page 189]]