[Code of Federal Regulations]
[Title 21, Volume 5]
[Revised as of April 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR320.26]

[Page 192-193]
 
                        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. 320.26  Guidelines on the design of a single-dose in vivo 
bioavailability or bioequivalence study.

    (a)  Basic principles. (1) An in vivo bioavailability or 
bioequivalence study should be a single-dose comparison of the drug 
product to be tested and the appropriate reference material conducted in 
normal adults.
    (2) The test product and the reference material should be 
administered to subjects in the fasting state, unless some other 
approach is more appropriate for valid scientific reasons.
    (b) Study design. (1) A single-dose study should be crossover in 
design, unless a parallel design or other design is more appropriate for 
valid scientific reasons, and should provide for a drug elimination 
period.
    (2) Unless some other approach is appropriate for valid scientific 
reasons, the drug elimination period should be either:
    (i) At least three times the half-life of the active drug ingredient 
or therapeutic moiety, or its metabolite(s), measured in the blood or 
urine; or
    (ii) At least three times the half-life of decay of the acute 
pharmacological effect.

[[Page 193]]

    (c) Collection of blood samples. (1) When comparison of the test 
product and the reference material is to be based on blood concentration 
time curves, unless some other approach is more appropriate for valid 
scientific reasons, blood samples should be taken with sufficient 
frequency to permit an estimate of both:
    (i) The peak concentration in the blood of the active drug 
ingredient or therapeutic moiety, or its metabolite(s), measured; and
    (ii) The total area under the curve for a time period at least three 
times the half-life of the active drug ingredient or therapeutic moiety, 
or its metabolite(s), measured.
    (2) In a study comparing oral dosage forms, the sampling times 
should be identical.
    (3) In a study comparing an intravenous dosage form and an oral 
dosage form, the sampling times should be those needed to describe both:
    (i) The distribution and elimination phase of the intravenous dosage 
form; and
    (ii) The absorption and elimination phase of the oral dosage form.
    (4) In a study comparing drug delivery systems other than oral or 
intravenous dosage forms with an appropriate reference standard, the 
sampling times should be based on valid scientific reasons.
    (d) Collection of urine samples. When comparison of the test product 
and the reference material is to be based on cumulative urinary 
excretion-time curves, unless some other approach is more appropriate 
for valid scientific reasons, samples of the urine should be collected 
with sufficient frequency to permit an estimate of the rate and extent 
of urinary excretion of the active drug ingredient or therapeutic 
moiety, or its metabolite(s), measured.
    (e) Measurement of an acute pharmacological effect. (1) When 
comparison of the test product and the reference material is to be based 
on acute pharmacological effect-time curves, measurements of this effect 
should be made with sufficient frequency to permit a reasonable estimate 
of the total area under the curve for a time period at least three times 
the half-life of decay of the pharmacological effect, unless some other 
approach is more appropriate for valid scientific reasons.
    (2) The use of an acute pharmacological effect to determine 
bioavailability may further require demonstration of dose-related 
response. In such a case, bioavailability may be determined by 
comparison of the dose-response curves as well as the total area under 
the acute pharmacological effect-time curves for any given dose.

[42 FR 1648, Jan. 7, 1977, as amended at 67 FR 77674, Dec. 19, 2002]