[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: 21CFR320.33]

[Page 196-197]
 
                        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. 320.33  Criteria and evidence to assess actual or potential 
bioequivalence problems.

    The Commissioner of Food and Drugs shall consider the following 
factors, when supported by well-documented evidence, to identify 
specific pharmaceutical equivalents and pharmaceutical alternatives that 
are not or may not be bioequivalent drug products.
    (a) Evidence from well-controlled clinical trials or controlled 
observations in patients that such drug products do not give comparable 
therapeutic effects.
    (b) Evidence from well-controlled bioequivalence studies that such 
products are not bioequivalent drug products.
    (c) Evidence that the drug products exhibit a narrow therapeutic 
ratio, e.g., there is less than a 2-fold difference in median lethal 
dose (LD50) and median effective dose (ED50) 
values, or have less than a 2-fold difference in the minimum toxic 
concentrations and minimum effective concentrations in the blood, and 
safe and effective use of the drug products requires careful dosage 
titration and patient monitoring.
    (d) Competent medical determination that a lack of bioequivalence 
would have a serious adverse effect in the treatment or prevention of a 
serious disease or condition.
    (e) Physicochemical evidence that:
    (1) The active drug ingredient has a low solubility in water, e.g., 
less than 5 milligrams per 1 milliliter, or, if dissolution in the 
stomach is critical to absorption, the volume of gastric fluids required 
to dissolve the recommended dose far exceeds the volume of fluids 
present in the stomach (taken to be 100

[[Page 197]]

milliliters for adults and prorated for infants and children).
    (2) The dissolution rate of one or more such products is slow, e.g., 
less than 50 percent in 30 minutes when tested using either a general 
method specified in an official compendium or a paddle method at 50 
revolutions per minute in 900 milliliters of distilled or deionized 
water at 37[deg] C, or differs significantly from that of an appropriate 
reference material such as an identical drug product that is the subject 
of an approved full new drug application.
    (3) The particle size and/or surface area of the active drug 
ingredient is critical in determining its bioavailability.
    (4) Certain physical structural characteristics of the active drug 
ingredient, e.g., polymorphic forms, conforms, solvates, complexes, and 
crystal modifications, dissolve poorly and this poor dissolution may 
affect absorption.
    (5) Such drug products have a high ratio of excipients to active 
ingredients, e.g., greater than 5 to 1.
    (6) Specific inactive ingredients, e.g., hydrophilic or hydrophobic 
excipients and lubricants, either may be required for absorption of the 
active drug ingredient or therapeutic moiety or, alternatively, if 
present, may interfere with such absorption.
    (f) Pharmacokinetic evidence that:
    (1) The active drug ingredient, therapeutic moiety, or its precursor 
is absorbed in large part in a particular segment of the 
gastrointestinal tract or is absorbed from a localized site.
    (2) The degree of absorption of the active drug ingredient, 
therapeutic moiety, or its precursor is poor, e.g., less than 50 
percent, ordinarily in comparison to an intravenous dose, even when it 
is administered in pure form, e.g., in solution.
    (3) There is rapid metabolism of the therapeutic moiety in the 
intestinal wall or liver during the process of absorption (first-class 
metabolism) so the therapeutic effect and/or toxicity of such drug 
product is determined by the rate as well as the degree of absorption.
    (4) The therapeutic moiety is rapidly metabolized or excreted so 
that rapid dissolution and absorption are required for effectiveness.
    (5) The active drug ingredient or therapeutic moiety is unstable in 
specific portions of the gastrointestinal tract and requires special 
coatings or formulations, e.g., buffers, enteric coatings, and film 
coatings, to assure adequate absorption.
    (6) The drug product is subject to dose dependent kinetics in or 
near the therapeutic range, and the rate and extent of absorption are 
important to bioequivalence.

[42 FR 1635, Jan. 7, 1977. Redesignated and amended at 57 FR 18001, Apr. 
28, 1992]