Guidance for Industry
Dissolution Testing of Immediate
Release Solid Oral Dosage Forms
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
August 1997
BP 1 Guidance for Industry
Dissolution Testing of Immediate
Release Solid Oral Dosage Forms
Additional copies are available from:
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5600 Fishers Lane
Rockville, MD  20857
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(Internet)  http://www.fda.gov/cder/guidance.htm
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
August 1997
BP 1 Table of Contents
I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
II. BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
III. BIOPHARMACEUTICS  CLASSIFICATION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 2
IV. SETTING DISSOLUTION SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
A. Approaches for Setting Dissolution Specifications for a New Chemical Entity . . . 4
B. Approaches for Setting Dissolution Specifications for Generic Products . . . . . . . 5
C. Special Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
D. Mapping or Response Surface Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
E. In Vivo-In Vitro Correlations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
F. Validation and Verification of Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
V. DISSOLUTION PROFILE COMPARISONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A. Model Independent Approach Using a Similarity Factor . . . . . . . . . . . . . . . . . . . 8
B. Model Independent Multivariate Confidence Region Procedure . . . . . . . . . . . . 10
C. Model Dependent Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
VI. DISSOLUTION AND SUPAC-IR  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
VII. BIOWAIVERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
REFERENCES
i GUIDANCE FOR INDUSTRY1
Dissolution Testing of Immediate Release
Solid Oral Dosage Forms
I. INTRODUCTION
This guidance is developed for immediate release (IR) dosage forms and is intended to provide 
(1) general recommendations for dissolution testing; (2) approaches for setting dissolution
specifications related to the biopharmaceutic characteristics of the drug substance; (3) statistical
methods for comparing dissolution profiles; and (4) a process to help determine when dissolution
testing is sufficient to grant a waiver for an in vivo bioequivalence study.  This document also
provides recommendations for dissolution tests to help ensure continuous drug product quality
and performance after certain postapproval manufacturing changes.  Summary information on
dissolution methodology, apparatus, and operating conditions for dissolution testing of IR
products is provided in summary form in Appendix A.  This guidance is intended to complement
the SUPAC - IR guidance for industry:  Immediate Release Solid Oral Dosage Forms:  Scale-up
and Post-Approval Changes:  Chemistry, Manufacturing and Controls, In Vitro Dissolution
Testing, and In Vivo Bioequivalence Documentation, with specific reference to the generation of
dissolution profiles for comparative purposes.
II. BACKGROUND
Drug absorption from a solid dosage form after oral administration depends on the release of the
drug substance from the drug product, the dissolution or solubilization of the drug under
physiological conditions, and the permeability across the gastrointestinal tract.  Because of the
critical nature of the first two of these steps, in vitro dissolution may be relevant to the prediction
of in vivo performance.  Based on this general consideration, in vitro dissolution tests for
immediate release solid oral dosage forms, such as tablets and capsules, are used to (1) assess the
lot-to-lot quality of a drug product; (2) guide development of new formulations; 
1This guidance has been prepared by the Immediate Release Expert Working Group of the Biopharmaceutics
Coordinating Committee in the Center for Drug Evaluation and Research (CDER) at the Food and Drug Administration. 
This guidance document represents the Agencys current thinking on the dissolution testing of immediate release solid
oral dosage forms.  It does not create or confer any rights for or on any person and does not operate to bind FDA or the
public.  An alternative approach may be used if such approach satisfies the requirements of the applicable statute,
regulations, or both. and (3) ensure continuing product quality and performance after certain changes, such as changes
in the formulation, the manufacturing process, the site of manufacture, and the scale-up of the
manufacturing process.
  
Current knowledge about the solubility, permeability, dissolution, and pharmacokinetics of a drug
product should be considered in defining dissolution test specifications for the drug approval
process.  This knowledge should also be used to ensure continued equivalence of the product, as
well as to ensure the product's sameness under certain scale-up and postapproval changes.  
New drug applications (NDAs) submitted to the Food and Drug Administration (FDA) contain
bioavailability data and in vitro dissolution data, that, together with chemistry, manufacturing, and
controls (CMC) data, characterize the quality and performance of the drug product.  In vitro
dissolution data are generally obtained from batches that have been used in pivotal clinical and/or
bioavailability studies and from other human studies conducted during product development. 
Acceptable bioequivalence data and comparable in vitro dissolution and CMC data are required
for approval of abbreviated new drug applications (ANDAs) (21 CFR 314.94).  The in vitro
specifications for generic products should be established based on a dissolution profile.  For new
drug applications, as well as generic drug applications, the dissolution specifications should be
based on acceptable clinical, bioavailability, and/or bioequivalence batches.
Once the specifications are established in an NDA, the dissolution specifications for batch-to-
batch quality assurance are published in the United States Pharmacopeia (USP) as compendial
standards, which become the official specifications for all subsequent IR products with the same
active ingredients.  In general, these compendial dissolution standards are single-point dissolution
tests, not profiles.
III. BIOPHARMACEUTICS  CLASSIFICATION SYSTEM
Based on drug solubility and permeability, the following Biopharmaceutics Classification System
(BCS) is recommended in the literature (Amidon 1995):
Case 1: High Solubility - High Permeability Drugs
Case 2: Low Solubility - High Permeability Drugs
Case 3: High Solubility - Low Permeability Drugs
Case 4: Low Solubility - Low Permeability Drugs
This classification can be used as a basis for setting in vitro dissolution specifications and can also
provide a basis for predicting the likelihood of achieving a successful in vivo-in vitro correlation
(IVIVC).  The solubility of a drug is determined by dissolving the highest unit dose of  the drug in
250 mL of buffer adjusted between pH 1.0 and 8.0.  A drug substance is considered highly soluble
when the dose/solubility volume of solution are less than or equal to 250 mL.   High-permeability
drugs are generally those with an extent of absorption that is greater than 90% in the absence of
2 documented instability in the gastrointestinal tract or those whose permeability has been
determined experimentally.  The BCS suggests that for high solubility, high permeability (case 1)
drugs and in some instances for high solubility, low permeability (case 3) drugs, 85% dissolution
in 0.1N HCl in 15 minutes can ensure that the bioavailability of the drug is not limited by
dissolution.  In these cases, the rate limiting step for drug absorption is gastric emptying.  
The mean T50% gastric residence (emptying) time is 15-20 minutes under fasting conditions. 
Based on this information, a  conservative conclusion is that a drug product undergoing 85%
dissolution in 15 minutes under mild dissolution test conditions in 0.1N HCl behaves like a 
solution and generally should not have any bioavailability problems.  If the dissolution is slower
than gastric emptying, a dissolution profile with multiple time points in multimedia is
recommended.
In the case of low solubility/high permeability drugs (case 2), drug dissolution may be the rate
limiting step for drug absorption and an IVIVC may be expected.  A dissolution profile in multiple
media is recommended for drug products in this category.  In the case of high solubility/low
permeability drugs (case 3), permeability is the rate controlling step and a limited IVIVC may be
possible, depending on the relative rates of dissolution and intestinal transit.  Drugs in case 4 (i.e.,
low solubility/low permeability drugs) present significant problems for oral drug delivery.
IV. SETTING DISSOLUTION SPECIFICATIONS
In vitro dissolution specifications are established to ensure batch-to-batch consistency and to
signal potential problems with in vivo bioavailability.  For NDAs, the dissolution specifications
should be based on acceptable clinical, pivotal bioavailability, and/or bioequivalence batches.  For
ANDAs/AADAs, the dissolution specifications should be based on the performance of acceptable
bioequivalence batches of the drug product.  The NDA dissolution specifications should be based
on experience gained during the drug development process and the in vitro performance of
appropriate test batches.  In the case of a generic drug product, the dissolution specifications are
generally the same as the reference listed drug (RLD).  The specifications are confirmed by testing
the dissolution performance of the generic drug product from an acceptable bioequivalence study. 
If the dissolution of the generic product is substantially different compared to that of the reference
listed drug and the in vivo data remain acceptable, a different dissolution specification for the
generic product may be set.  Once a dissolution specification is set, the drug product should
comply with that specification throughout its shelf life.
The International Conference on Harmonisation (ICH) Q1A guideline (Stability Testing of New
Drug Substances and Drug Products) has recommended that for an NDA, three batches (two
pilot and one smaller scale) be placed into stability testing.  These batches also may be used to set
dissolution specifications when a suitable bioequivalence relationship exists between these batches
and both the pivotal clinical trial batch and the drug product intended for the market.
3 Three catagories of dissolution test specifications for immediate release drug products are
described in the guidance.
! Single-point specifications
As a routine quality control test.  (For highly soluble and rapidly dissolving drug
products.)
! Two-point specifications
1. For characterizing the quality of the drug product.
2. As a routine quality control test for certain types of drug products (e.g., slow 
dissolving or poorly water soluble drug product like carbamazepine).
! Dissolution profile comparison
1. For accepting product sameness under SUPAC-related changes.
2. To waive bioequivalence requirements for lower strengths of a dosage form.
3. To support waivers for other bioequivalence requirements.
In the future, a two-time point approach may be useful, both to characterize a drug product and
to serve as quality control specification.
A. Approaches for Setting Dissolution Specifications for a New Chemical Entity
Dissolution methodology and specifications developed by a sponsor are presented in the
biopharmaceutics section (21 CFR 320.24(b)(5)), and the chemistry, manufacturing, and
controls section (21 CFR 314.50(d)(1)(ii)(a)) of an NDA.  The dissolution characteristics
of the drug product should be developed based on consideration of the pH solubility
profile and pKa of the drug substance.  The drug permeability or octanol/water partition
coefficient measurement may be useful in selecting the dissolution methodology and
specifications. The dissolution specifications are established in consultation with
biopharmaceutics and CMC review staff in the Office of Pharmaceutical Science (OPS). 
For NDAs, the specifications should be based on the dissolution characteristics of batches
used in pivotal clinical trials and/or in confirmatory bioavailability studies.  If the
formulation intended for marketing differs significantly from the drug product used in
pivotal clinical trials, dissolution and bioequivalence testing between the two formulations
are recommended.
4 Dissolution testing should be carried out under mild test conditions, basket method at
50/100 rpm or paddle method at 50/75 rpm, at 15-minute intervals, to generate a
dissolution profile.  For rapidly dissolving products, generation of an adequate profile
sampling at 5- or 10-minute intervals may be necessary.  For highly soluble and rapidly
dissolving drug products (BCS classes 1 and 3), a single-point dissolution test
specification of NLT 85% (Q=80%) in 60 minutes or less is sufficient as a routine quality
control test for batch-to-batch uniformity.  For slowly dissolving or poorly water soluble
drugs (BCS class 2), a two-point dissolution specification, one at 15 minutes to include a
dissolution range (a dissolution window) and the other at a later point (30, 45, or 60
minutes) to ensure 85% dissolution, is recommended to characterize the quality of the
product.  The product is expected to comply with dissolution specifications throughout its
shelf life.  If the dissolution characteristics of the drug product change with time, whether
or not the specifications should be altered will depend on demonstrating bioequivalence of
the changed product to the original biobatch or pivotal batch.  To ensure continuous
batch-to-batch equivalence of the product after scale-up and postapproval changes in the
marketplace, dissolution profiles should remain comparable to those of the approved
biobatch or pivotal clinical trial batch(es).  
B. Approaches for Setting Dissolution Specifications for Generic Products
The approaches for setting dissolution specifications for generic products fall into three
categories, depending on whether an official compendial test for the drug product exists
and on the nature of the dissolution test employed for the reference listed drug.  All
approved new drug products should meet current USP dissolution test requirements, if
they exist.  The three categories are:
1. USP Drug Product Dissolution Test Available
In this instance, the quality control dissolution test is the test described in the USP. 
The Division of Bioequivalence, Office of Generic Drugs, also recommends taking
a dissolution profile at 15-minute intervals or less using the USP method for test
and reference products (12 units each).  The Division of Bioequivalence may also
recommend submitting additional dissolution data when scientifically justified. 
Examples of this include (1) cases in which USP does not specify a dissolution test
for all active drug substances of a combination product and (2) cases in which USP
specifies use of disintegration apparatus.
2. USP Drug Product Dissolution Test Not Available; Dissolution Test for
Reference Listed NDA Drug Product Publicly Available
In this instance, a dissolution profile at 15-minute intervals of test and reference
products (12 units each) using the method approved for the reference listed
product is recommended.  The Division of Bioequivalence may also request
5 submission of additional dissolution testing data as a condition of approval, when
scientifically justified.   
3. USP Drug Product Dissolution Test Not Available; Dissolution Test for
Reference Listed NDA Drug Product Not Publicly Available
In this instance, comparative dissolution testing using test and reference products
under a variety of test conditions is recommended.  The test conditions may
include different dissolution media (pH 1 to 6.8), addition of surfactant, and use of
apparatus 1 and 2 with varying agitation.  In all cases, profiles should be generated
as previously recommended.  The dissolution specifications are set based on the
available bioequivalence and other data. 
C. Special Cases
1. Two-Point Dissolution Test
For poorly water soluble drug products (e.g., carbamazapine), dissolution testing
at more than one time point for routine quality control is recommended to ensure
in vivo product performance.  Alternatively, a dissolution profile may be used for
purposes of quality control.
2. Two-Tiered Dissolution Test
To more accurately reflect the physiologic conditions of the gastrointestinal tract,
two-tiered dissolution testing in simulated gastric fluid (SGF) with and without
pepsin or simulated intestinal fluid (SIF) with and without pancreatin may be
employed to assess batch-to-batch product quality provided the bioequivalence is
maintained. 
Recent examples involving soft and hard gelatin capsules show a decrease in the
dissolution profile over time either in SGF or in SIF without enzymes.  This has
been attributed to pellicle formation.  When the dissolution of aged or slower
releasing capsules was carried out in the presence of an enzyme (pepsin in SGF or
pancreatin in SIF), a significant increase in the dissolution was observed.  In this
setting, multiple dissolution media may be necessary to adequately assess product
quality.
D. Mapping or Response Surface Methodology
Mapping is defined as a process for determining the relationship between critical
manufacturing variables (CMV) and a response surface derived from an in vitro
dissolution profile and an in vivo bioavailability data set.  The CMV include changes in the
6 formulation, process, equipment, materials, and methods for the drug product that can
significantly affect in vitro dissolution (Skelly 1990, Shah 1992).  The goal is to develop
product specifications that will ensure bioequivalence of future batches prepared within
the limits of acceptable dissolution specifications.  Several experimental designs are
available to study the influence of CMV on product performance.  One approach to study
and evaluate the mapping process includes (1) prepare two or more dosage formulations
using CMV to study their in vitro dissolution characteristics; (2) test the products with
fastest and slowest dissolution characteristics along with the standard or the to be
marketed dosage form in small groups (e.g., n> 12) of human subjects; and (3) determine
the bioavailability of the products and in vitro-in vivo relationship.  The products with
extreme dissolution characteristics are also referred to as side batches (Siewert 1995).   If
the products with the extreme range of dissolution characteristics are found to be
bioequivalent to the standard or the to be marketed dosage form, future batches with
dissolution characteristics between these ranges should be equivalent to one another.  This
approach can be viewed as verifying the limits of the dissolution specifications.  Product
dissolution specifications established using a mapping approach will provide maximum
likelihood of ensuring stable quality and product performance.  Depending on the number
of products evaluated, the mapping study can provide information on in vitro-in vivo
correlations and/or a rank order relationship between in vivo and in vitro data.
E. In Vivo-In Vitro Correlations
For highly water soluble (BCS classes 1 and 3) immediate release products using currently
available excipients and manufacturing technology, an IVIVC may not be possible.  For
poorly water soluble products, BCS class 2, an IVIVC may be possible.
The value of dissolution as a quality control tool for predicting in vivo performance of a
drug product is significantly enhanced if an in vitro-in vivo relationship (correlation or
association) is established.  The in vitro test serves as a tool to distinguish between
acceptable and unacceptable drug products.  Acceptable products are bioequivalent, in
terms of in vivo performance, whereas unacceptable products are not.  To achieve an in
vitro-in vivo correlation, at least three batches that differ in the in vivo as well as the in
vitro performance should be available.  If the batches show differences in in vivo
performance, then in vitro test conditions can be modified to correspond with the in vivo
data to achieve an in vitro-in vivo correlation.  If no difference is found in the in vivo
performance of the batches and if the in vitro performance is different, it may be possible
to modify test conditions to achieve the same dissolution performance of the batches
studied in vivo.  Very often, the in vitro dissolution test is found to be more sensitive and
discriminating than the in vivo test.  From a quality assurance point of view, a more
discriminative dissolution method is preferred, because the test will indicate possible
changes in the quality of the product before in vivo performance is affected.
7 F. Validation and Verification of Specifications
Confirmation by in vivo studies may be needed for validation of an in vitro system.  In this
situation, the same formulation should be used but nonformulation CMV should be varied. 
Two batches with different in vitro profiles should be prepared (mapping approach). 
These products should then be tested in vivo.  If the two products show different in vivo
characteristics, then the system is validated.  In contrast, if there is no difference in the  in
vivo performance, the results can be interpreted as verifying the dissolution specification
limits as discussed under mapping.  Thus, either validation or verification of dissolution
specifications should be confirmed.
V. DISSOLUTION PROFILE COMPARISONS
Until recently, single-point dissolution tests and specifications have been employed in evaluating
scale-up and postapproval changes, such as (1) scale-up, (2) manufacturing site changes, (3)
component and composition changes, and (4) equipment and process changes.  A changed
product may also be a lower strength of a previously approved drug product.  In the presence of
certain minor changes, the single-point dissolution test may be adequate to ensure unchanged
product quality and performance.  For more major changes, a dissolution profile comparison
performed under identical conditions for the product before and after the change(s) is
recommended (see SUPAC-IR).  Dissolution profiles may be considered similar by virtue of (1)
overall profile similarity and (2) similarity at every dissolution sample time point.  The dissolution
profile comparison may be carried out using model independent or model dependent methods.
A. Model Independent Approach Using a Similarity Factor
A simple model independent approach uses a difference factor (f ) and a similarity factor
1
(f )  to  compare  dissolution  profiles  (Moore  1996).    The  difference  factor  (f ) calculates the
2 1
percent (%) difference between the two curves at each time point and is a measurement of
the relative error between the two curves:
         
            f   =  {[3 n  |  R  -  T  |  ]/[3 n  R ]}C 100                     
1 t=1 t t t=1 t
                                                  
where n is the number of time points, R is the dissolution value of the reference
t
(prechange) batch at time t, and T is the dissolution value of the test (postchange) batch
t  
at time t. 
 
The similarity factor (f ) is a logarithmic reciprocal square root transformation of the sum
2
of squared error and is a measurement of the similarity in the percent (%) dissolution
between the two curves.
           
  f   =    50  C  log  {[1+(1/n)3 n  (  R  -  T )2 ]-0.5C 100}      
2 t=1 t t
8 A specific procedure to determine difference and similarity factors is as follows:
1. Determine the dissolution profile of two products (12 units each) of the
test (postchange) and reference (prechange) products.
2. Using the mean dissolution values from both curves  at each time interval,
calculate the difference factor (f )  and  similarity  factor  (f ) using the above
1 2
equations.
3. For curves to be considered similar, f   values  should  be  close  to  0,  and  f
1 2
values should be close to 100.  Generally, f   values  up  to  15  (0-15)  and  f  values
1 2
greater than 50 (50-100) ensure sameness or equivalence of the two curves and,
thus, of the performance of the test (postchange) and reference (prechange)
products.
This model independent method is most suitable for dissolution profile comparison
when three to four or more dissolution time points are available. As further
suggestions for the general approach, the following recommendations should also
be considered:
! The dissolution measurements of the test and reference batches should be
made under exactly the same conditions.  The dissolution time points for
both the profiles should be the same (e.g., 15, 30, 45, 60 minutes).  The
reference batch used should be the most recently manufactured prechange
product.
! Only one measurement should be considered after 85% dissolution of both
the products.
! To allow use of mean data, the percent coefficient of variation at the earlier
time points (e.g., 15 minutes) should not be more than 20%, and at other
time points should not be more than 10%.
! The mean dissolution values for R can be derived either from (1) last
t
prechange (reference) batch or (2) last two or more consecutively
manufactured prechange batches.
B. Model Independent Multivariate Confidence Region Procedure
In instances where within batch variation is more than 15% CV, a multivariate model
independent procedure is more suitable for dissolution profile comparison.  The following
steps are suggested:
9 1. Determine the similarity limits in terms of multivariate statistical distance
(MSD) based on interbatch differences in dissolution from reference
(standard approved) batches.
 
2. Estimate the MSD between the test and reference mean dissolutions.
3. Estimate 90% confidence interval of true MSD between test and reference
batches.
4. Compare the upper limit of the confidence interval with the similarity limit. 
The test batch is considered similar to the reference batch if the upper limit of the
confidence interval is less than or equal to the similarity limit.
 
C. Model Dependent Approaches
Several mathematical models have been described in the literature to fit dissolution
profiles.  To allow application of these models to comparison of dissolution profiles, the
following procedures are suggested:
1. Select the most appropriate model for the dissolution profiles from the
standard, prechange, approved batches.  A model with no more than three
parameters (such as linear, quadratic, logistic, probit, and Weibull models) is
recommended.
2. Using data for the profile generated for each unit, fit the data to the most
appropriate model.
3. A similarity region is set based on variation of parameters of the fitted
model for test units (e.g., capsules or tablets) from the standard approved batches.
4. Calculate the MSD in model parameters between test and reference
batches.
5. Estimate the 90% confidence region of the true difference between the two
batches.
6. Compare the limits of the confidence region with the similarity region.  If
the confidence region is within the limits of the similarity region, the test batch is
considered to have a similar dissolution profile to the reference batch.
10 VI. DISSOLUTION AND SUPAC-IR 
The SUPAC-IR guidance defines the levels of changes, recommended tests, and filing
documentation to ensure product quality and performance of reference (prechange product) with
postapproval changes in (1) components and composition, (2) site of manufacturing, (3) the scale
of manufacturing, and (4) process and equipment changes in the manufacturing of immediate
release products (FDA 1995).  Depending on the level of change and the biopharmaceutics
classification system of the active drug substance, the SUPAC-IR guidance recommends different
levels of in vitro dissolution test and/or in vivo bioequivalence studies.  Tests vary depending on
therapeutic range and solubility and permeability factors of the drug substance.  For formulation
changes beyond those listed in the guidance, additional dissolution profile determinations in
several media are recommended.  For manufacturing site changes, scale-up equipment changes,
and minor process changes, only dissolution testing should be sufficient to ensure unchanged
product quality and performance.  The SUPAC-IR guidance recommends dissolution profile
comparisons for approving different levels of changes and documenting product sameness
between the test (postchange) and reference (prechange) product.  It recommends dissolution
profile comparisons using a model independent approach and the similarity factor (f ).
2
VII. BIOWAIVERS
In addition to routine quality control tests, comparative dissolution tests have been used to waive
bioequivalence requirements (biowaivers) for lower strengths of a dosage form.  For biowaivers, a
dissolution profile should be generated and evaluated using one of the methods described under
Section V in this guidance, "Dissolution Profile Comparisons."  Biowaivers are generally provided
for multiple strengths after approval of a bioequivalence study performed on one strength, using
the following criteria:
For multiple strengths of IR products with linear kinetics, the bioequivalence study may be
performed at the highest strength and waivers of in vivo studies may be granted on lower
strengths, based on an adequate dissolution test, provided the lower strengths are proportionately
similar in composition (21 CFR 320.22(d)(2)).  Similar may also be interpreted to mean that the
different strengths of the products are within the scope of changes permitted under the category
"Components and Composition," discussed in the SUPAC-IR guidance.  In all cases, the approval
of additional strengths is based on dissolution profile comparisons between these additional
strengths and the strength of the batch used in the pivotal bioequivalence study.
11 Appendix A
Dissolution Testing Conditions
Apparatus
The most commonly employed dissolution test methods are (1) the basket method (Apparatus 1)
and (2) the paddle method (Apparatus 2) (Shah 1989).  The basket and the paddle methods are
simple, robust, well standardized, and used worldwide.  These methods are flexible enough to
allow dissolution testing for a variety of drug products.  For this reason, the official in vitro
dissolution methods described in U.S. Pharmacopeia (USP), Apparatus 1 and Apparatus 2 should
be used unless shown to be unsatisfactory.  The in vitro dissolution procedures, such as the
reciprocating cylinder (Apparatus 3) and a flow-through cell system (Apparatus 4) described in
the USP, may be considered if needed.  These methodologies or other alternatives/modifications
should be considered on the basis of their proven superiority for a particular product.  Because of
the diversity of biological and formulation variables and the evolving nature of understanding in
this area, different experimental modifications may need to be carried out to obtain a suitable in
vivo correlation with in vitro release data.  Dissolution methodologies and apparatus described in
the USP can generally be used either with manual sampling or with automated procedures.
Dissolution Medium
Dissolution testing should be carried out under physiological conditions, if possible.  This allows
interpretation of dissolution data with regard to in vivo performance of the product.  However,
strict adherence to the gastrointestinal environment need not be used in routine dissolution
testing.  The testing conditions should be based on physicochemical characteristics of the drug
substance and the environmental conditions the dosage form might be exposed to after oral
administration.
The volume of the dissolution medium is generally 500, 900, or 1000 mL.  Sink conditions are
desirable but not mandatory.  An aqueous medium with pH range 1.2 to 6.8 (ionic strength of
buffers the same as in USP) should be used.  To simulate intestinal fluid (SIF), a dissolution
medium of pH 6.8 should be employed.  A higher pH should be justified on a case-by-case basis
and, in general, should not exceed pH 8.0.  To simulate gastric fluid (SGF), a dissolution medium
of pH 1.2 should be employed without enzymes.  The need for enzymes in SGF and SIF should be
evaluated on a case-by-case basis and should be justified.  Recent experience with gelatin capsule
products indicates the possible need for enzymes (pepsin with SGF and pancreatin with SIF) to
dissolve pellicles, if formed, to permit the dissolution of the drug.  Use of water as a dissolution
medium also is discouraged because test conditions such as pH and surface tension can vary
depending on the source of water and may change during the dissolution test itself, due to the
influence of the active and inactive ingredients.  For water insoluble or sparingly water soluble
drug products, use of a surfactant such as sodium lauryl sulfate is recommended (Shah 1989,
1995).  The need for and the amount of the surfactant should be justified.  Use of a hydro
alcoholic medium is discouraged. 
A-1 All dissolution tests for IR dosage forms should be conducted at 370.5C.  The basket and
paddle method can be used for performing dissolution tests under multimedia conditions (e.g., the
initial dissolution test can be carried out at pH 1.2, and, after a suitable time interval, a small
amount of buffer can be added to raise pH to 6.8).  Alternatively, if addition of an enzyme is
desired, it can be added after initial studies (without enzymes).  Use of Apparatus 3 allows easy
change of the medium.  Apparatus 4 can also be adopted for a change in dissolution medium
during the dissolution run.
Certain drug products and formulations are sensitive to dissolved air in the dissolution medium
and will need deaeration.  In general, capsule dosage forms tend to float during dissolution testing
with the paddle method.  In such cases, it is recommended that a few turns of a wire helix (USP)
around the capsule be used.
The apparatus suitability tests should be carried out with a performance standard (i.e., calibrators)
at least twice a year and after any significant equipment change or movement.  However, a change
from basket to paddle or vice versa may need recalibration.  The equipment and dissolution
methodology should include the product related operating instructions such as deaeration of the
dissolution medium and use of a wire helix for capsules.  Validation of automated procedures
compared to the manual procedures should be well documented.  Validation of determinative
steps in the dissolution testing process should comply with the set standards for analytical
methodology.
Agitation
In general, mild agitation conditions should be maintained during dissolution testing to allow
maximum discriminating power and to detect products with poor in vivo performance.  Using the
basket method, the common agitation (or stirring speed) is 50-100 rpm; with the paddle method,
it is 50-75 rpm (Shah et al., 1992).  Apparatus 3 and 4 are seldom used to assess the dissolution
of immediate release drug products.
Validation
Validation of the dissolution apparatus/methodology should include (1) the system suitability test
using calibrators; (2) deaeration, if necessary; (3) validation between manual and automated
procedures; and (4) validation of a determinative step (i.e., analytical methods employed in
quantitative analysis of dissolution samples).  This should include all appropriate steps and
procedures of analytical methods validation.
A-2 REFERENCES
Amidon, G. L., H. Lennernas, V. P. Shah, and J. R. Crison, 1995, "A Theoretical Basis For 
a Biopharmaceutic Drug Classification:  The Correlation of In Vitro Drug Product
Dissolution and In Vivo Bioavailability," Pharmaceutical Research, 12:413-420.
FDA, 1995, Center for Drug Evaluation and Research, Guidance for Industry:  Immediate 
Release Solid Oral Dosage Forms.  Scale-up and Post-Approval Changes: Chemistry,
Manufacturing and Controls, In Vitro Dissolution Testing, and In Vivo Bioequivalence
Documentation [SUPAC-IR], November 1995.
Meyer, M. C., A. B. Straughn, E. J. Jarvi, G. C. Wood, F. R. Pelsor, and V. P. Shah, 1992, 
"The Bioequivalence of Carbamazepine Tablets with a History of Clinical Failures,"
Pharmaceutical Research, 9:1612-1616.
Moore, J. W. and H. H. Flanner, 1996, "Mathematical Comparison of Dissolution Profiles," 
Pharmaceutical Technology,  20 (6):64-74.
Shah, V. P., et al., 1989, "In Vitro Dissolution Profile of Water Insoluble Drug Dosage Forms in
the Presence of Surfactants," Pharmaceutical Research, 6:612-618.
Shah, V. P., et al., 1992, "Influence of Higher Rate of Agitation on Release Patterns of Immediate
Release Drug Products," Journal of Pharmaceutical Science, 81:500-503.
                 
Shah, V. P., J. P. Skelly, W. H. Barr, H. Malinowski, and G. L. Amidon, 1992, "Scale-up 
of Controlled Release Products - Preliminary Considerations," Pharmaceutical
Technology, 16(5):35-40.
Shah, V. P., et al., 1995, "In Vivo Dissolution of Sparingly Water Soluble Drug Dosage Forms,"
International Journal of Pharmaceutics, 125:99-106. 
Siewert, M., 1995, "FIP Guidelines for Dissolution Testing of Solid Oral Products," Pharm. 
Ind.  57:362-369.
Skelly, J. P., G. L. Amidon, W. H. Barr, L. Z. Benet, J. E. Carter, J. R. Robinson, V. P. Shah, and
A. Yacobi, 1990, "In Vitro and In Vivo Testing and Correlation for Oral Controlled/Modified-
Release Dosage Forms," Pharmaceutical Research, 7:975-982.
United States Pharmacopeia (USP), U.S. Pharmacopeial Convention, Inc.  Rockville, MD.