Guidance for Industry
Q1B Photostability Testing of New
Drug Substances and Products
November 1996
ICH Guidance for Industry
Q1B Photostability Testing of New
Drug Substances and Products
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November  1996
ICH Table of Contents
I. GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
A. Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
B. Light Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
C. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
II. DRUG SUBSTANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
A. Presentation of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
B. Analysis of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
C. Judgment of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
III. DRUG PRODUCT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
A. Presentation of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
B. Analysis of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
C. Judgment of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
IV. ANNEX:  Quinine Chemical Actinometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
V. GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
VI. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
i GUIDANCE FOR INDUSTRY1
Q1B Photostability Testing of New Drug
Substances and Products
I. GENERAL
The ICH Harmonized Tripartite Guideline on Stability Testing of New Drug Substances and
Products (hereafter referred to as the parent guideline) notes that light testing should be an
integral part of stress testing.  This document is an annex to the parent guideline and addresses the
recommendations for photostability testing.
A. Preamble
The intrinsic photostability characteristics of new drug substances and products should be
evaluated to demonstrate that, as appropriate, light exposure does not result in
unacceptable change.  Normally, photostability testing is carried out on a single batch of
material selected as described under "Selection of Batches" in the parent guideline.  Under
some circumstances these studies should be repeated if certain variations and changes are
made to the product (e.g., formulation, packaging).  Whether these studies should be
repeated depends on the photostability characteristics determined at the time of initial
filing and the type of variation and/or change made.
The guideline primarily addresses the generation of photostability information for
submission in registration applications for new molecular entities and associated drug
products.  The guideline does not cover the photostability of drugs after administration
(i.e., under conditions of use) and those applications not covered by the parent guideline. 
Alternative approaches may be used if they are scientifically sound and justification is
provided.
1This guidance was developed within the Expert Working Group (Quality) of the International Conference on
Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) and has been
subject to consultation by the regulatory parties, in accordance with the ICH process.  This document has been endorsed
by the ICH Steering Committee at Step 4 of the ICH process, November 1996.  At Step 4 of the process, the final draft is
recommended for adoption to the regulatory bodies of the European Union, Japan, and the United States.  This guidance
was published in the Federal Register on May 16, 1997 (62 FR 27116), and is applicable to drug and biological
products.  This guidance represents the Agencys current thinking on photostability testing of new drug substances and
products.  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.
1 A systematic approach to photostability testing is recommended covering, as appropriate,
studies such as:
(i) Tests on the drug substance;
(ii) Tests on the exposed drug product outside of the immediate pack; and if
necessary,
(iii) Tests on the drug product in the immediate pack; and if necessary,
(iv) Tests on the drug product in the marketing pack.
The extent of drug product testing should be established by assessing whether or not
acceptable change has occurred at the end of the light exposure testing as described in the
Decision Flow Chart for Photostability Testing of Drug Products.  Acceptable change is
change within limits justified by the applicant.
The formal labeling requirements for photolabile drug substances and drug products are
established by national/regional requirements.
2 3 B. Light Sources
The light sources described below may be used for photostability testing.  The applicant
should either maintain an appropriate control of temperature to minimize the effect of
localized temperature changes or include a dark control in the same environment unless
otherwise justified.  For both options 1 and 2, a pharmaceutical manufacturer/applicant
may rely on the spectral distribution specification of the light source manufacturer.
Option 1
Any light source that is designed to produce an output similar to the D65/ID65
emission standard such as an artificial daylight fluorescent lamp combining visible
and ultraviolet (UV) outputs, xenon, or metal halide lamp.  D65 is the
internationally recognized standard for outdoor daylight as defined in ISO 10977
(1993).  ID65 is the equivalent indoor indirect daylight standard.  For a light
source emitting significant radiation below 320 nanometers (nm), an appropriate
filter(s) may be fitted to eliminate such radiation.
Option 2
For option 2 the same sample should be exposed to both the cool white fluorescent
and near ultraviolet lamp.
1. A cool white fluorescent lamp designed to produce an output similar to
that specified in ISO 10977 (1993); and
2. A near UV fluorescent lamp having a spectral distribution from 320 nm to
400 nm with a maximum energy emission between 350 nm and 370 nm; a
significant proportion of UV should be in both bands of 320 to 360 nm and
360 to 400 nm.
C. Procedure
For confirmatory studies, samples should be exposed to light providing an overall
illumination of not less than 1.2 million lux hours and an integrated near ultraviolet energy
of not less than 200 watt hours/square meter to allow direct comparisons to be made
between the drug substance and drug product.
Samples may be exposed side-by-side with a validated chemical actinometric system to
ensure the specified light exposure is obtained, or for the appropriate duration of time
when conditions have been monitored using calibrated radiometers/lux meters.  An
example of an actinometric procedure is provided in the Annex.
4 If protected samples (e.g., wrapped in aluminum foil) are used as dark controls to evaluate
the contribution of thermally induced change to the total observed change, these should be
placed alongside the authentic sample.
II. DRUG SUBSTANCE
For drug substances, photostability testing should consist of two parts:  Forced degradation
testing and confirmatory testing.
The purpose of forced degradation testing studies is to evaluate the overall photosensitivity of the
material for method development purposes and/or degradation pathway elucidation.  This testing
may involve the drug substance alone and/or in simple solutions/suspensions to validate the
analytical procedures.  In these studies, the samples should be in chemically inert and transparent
containers.  In these forced degradation studies, a variety of exposure conditions may be used,
depending on the photosensitivity of the drug substance involved and the intensity of the light
sources used.  For development and validation purposes, it is appropriate to limit exposure and
end the studies if extensive decomposition occurs.  For photostable materials, studies may be
terminated after an appropriate exposure level has been used.  The design of these experiments is
left to the applicant's discretion although the exposure levels used should be justified.
Under forcing conditions, decomposition products may be observed that are unlikely to be formed
under the conditions used for confirmatory studies.  This information may be useful in developing
and validating suitable analytical methods.  If in practice it has been demonstrated they are not
formed in the confirmatory studies, these degradation products need not be examined further.
Confirmatory studies should then be undertaken to provide the information necessary for
handling, packaging, and labeling (see section I.C., Procedure, and II.A., Presentation, for
information on the design of these studies).
Normally, only one batch of drug substance is tested during the development phase, and then the
photostability characteristics should be confirmed on a single batch selected as described in the
parent guideline if the drug is clearly photostable or photolabile.  If the results of the confirmatory
study are equivocal, testing of up to two additional batches should be conducted.  Samples should
be selected as described in the parent guideline.
A. Presentation of Samples
Care should be taken to ensure that the physical characteristics of the samples under test
are taken into account and efforts should be made, such as cooling and/or placing the
samples in sealed containers, to ensure that the effects of the changes in physical states
such as sublimation, evaporation, or melting are minimized.  All such precautions should
be chosen to provide minimal interference with the exposure of samples under test. 
5 Possible interactions between the samples and any material used for containers or for
general protection of the sample should also be considered and eliminated wherever not
relevant to the test being carried out.
As a direct challenge for samples of solid drug substances, an appropriate amount of
sample should be taken and placed in a suitable glass or plastic dish and protected with a
suitable transparent cover if considered necessary.  Solid drug substances should be spread
across the container to give a thickness of typically not more than 3 millimeters.  Drug
substances that are liquids should be exposed in chemically inert and transparent
containers.
B. Analysis of Samples
At the end of the exposure period, the samples should be examined for any changes in
physical properties (e.g., appearance, clarity or color of solution) and for assay and
degradants by a method suitably validated for products likely to arise from photochemical
degradation processes.
Where solid drug substance samples are involved, sampling should ensure that a
representative portion is used in individual tests.  Similar sampling considerations, such as
homogenization of the entire sample, apply to other materials that may not be
homogeneous after exposure.  The analysis of the exposed sample should be performed
concomitantly with that of any protected samples used as dark control if these are used in
the test.
C. Judgment of Results
The forced degradation studies should be designed to provide suitable information to
develop and validate test methods for the confirmatory studies.  These test methods
should be capable of resolving and detecting photolytic degradants that appear during the
confirmatory studies.  When evaluating the results of these studies, it is important to
recognize that they form part of the stress testing and are not therefore designed to
establish qualitative or quantitative limits for change.
The confirmatory studies should identify precautionary measures needed in manufacturing
or in formulation of the drug product, and if light resistant packaging is needed.  When
evaluating the results of confirmatory studies to determine whether change due to
exposure to light is acceptable, it is important to consider the results from other formal
stability studies in order to assure that the drug will be within justified limits at time of use
(see the relevant ICH Stability and Impurity Guidelines).
6 III. DRUG PRODUCT
Normally, the studies on drug products should be carried out in a sequential manner starting with
testing the fully exposed product then progressing as necessary to the product in the immediate
pack and then in the marketing pack.  Testing should progress until the results demonstrate that
the drug product is adequately protected from exposure to light.  The drug product should be
exposed to the light conditions described under the procedure in section I.C.
Normally, only one batch of drug product is tested during the development phase, and then the
photostability characteristics should be confirmed on a single batch selected as described in the
parent guideline if the product is clearly photostable or photolabile.  If the results of the
confirmatory study are equivocal, testing of up to two additional batches should be conducted.
For some products where it has been demonstrated that the immediate pack is completely
impenetrable to light, such as aluminum tubes or cans, testing should normally only be conducted
on directly exposed drug product.
It may be appropriate to test certain products, such as infusion liquids or dermal creams, to
support their photostability in-use.  The extent of this testing should depend on and relate to the
directions for use, and is left to the applicant's discretion.
The analytical procedures used should be suitably validated.
A. Presentation of Samples
Care should be taken to ensure that the physical characteristics of the samples under test
are taken into account and efforts, such as cooling and/or placing the samples in sealed
containers, should be made to ensure that the effects of the changes in physical states are
minimized, such as sublimation, evaporation, or melting.  All such precautions should be
chosen to provide minimal interference with the irradiation of samples under test.  Possible
interactions between the samples and any material used for containers or for general
protection of the sample should also be considered and eliminated wherever not relevant
to the test being carried out.
Where practicable when testing samples of the drug product outside of the primary pack,
these should be presented in a way similar to the conditions mentioned for the drug
substance.  The samples should be positioned to provide maximum area of exposure to the
light source.  For example, tablets, capsules, should be spread in a single layer.
If direct exposure is not practical (e.g., due to oxidation of a product), the sample should
be placed in a suitable protective inert transparent container (e.g., quartz).
7 If testing of the drug product in the immediate container or as marketed is needed, the
samples should be placed horizontally or transversely with respect to the light source,
whichever provides for the most uniform exposure of the samples.  Some adjustment of
testing conditions may have to be made when testing large volume containers (e.g.,
dispensing packs).
B. Analysis of Samples
At the end of the exposure period, the samples should be examined for any changes in
physical properties (e.g., appearance, clarity, or color of solution,
dissolution/disintegration for dosage forms such as capsules) and for assay and degradants
by a method suitably validated for products likely to arise from photochemical degradation
processes.
When powder samples are involved, sampling should ensure that a representative portion
is used in individual tests.  For solid oral dosage form products, testing should be
conducted on an appropriately sized composite of, for example, 20 tablets or capsules. 
Similar sampling considerations, such as homogenization or solubilization of the entire
sample, apply to other materials that may not be homogeneous after exposure (e.g.,
creams, ointments, suspensions).  The analysis of the exposed sample should be performed
concomitantly with that of any protected samples used as dark controls if these are used in
the test.
C. Judgment of Results
Depending on the extent of change, special labeling or packaging may be needed to
mitigate exposure to light.  When evaluating the results of photostability studies to
determine whether change due to exposure to light is acceptable, it is important to
consider the results obtained from other formal stability studies in order to assure that the
product will be within proposed specifications during the shelf life (see the relevant ICH
Stability and Impurity Guidelines).
IV. ANNEX:  Quinine Chemical Actinometry
The following provides details of an actinometric procedure for monitoring exposure to a
near UV flourescentofamp (based on FDA/National Institute of Standards and Technology
study).  For other light sources/actinometric systems, the same approach may be used, but
each actinometric system should be calibrated for the light source used.
Prepare a sufficient quantity of a 2 percent weight/volume aqueous solution of quinine
monohydrochloride dihydrate (if necessary, dissolve by heating).  
8 Option 1
Put 10 milliliters (mL) of the solution into a 20 mL colorless ampoule, seal it
hermetically, and use this as the sample.  Separately, put 10 mL of the solution into
a 20 mL colorless ampoule (see note 1), seal it hermetically, wrap in aluminum foil
to protect completely from light, and use this as the control.  Expose the sample
and control to the light source for an appropriate number of hours.  After exposure
determine the absorbances of the sample (A )  and  the  control  (A ) at 400 nm using
T O
a 1 centimeter (cm) pathlength.  Calculate the change in absorbance, ) A = A  -
T
A .  The length of exposure should be sufficient to ensure a change in absorbance
O
of at least 0.9.
Option 2
Fill a 1 cm quartz cell and use this as the sample.  Separately fill a 1 cm quartz cell,
wrap in aluminum foil to protect completely from light, and use this as the control. 
Expose the sample and control to the light source for an appropriate number of
hours.  After exposure determine the absorbances of the sample (A ) and the
T
control (A )  at  400  nm.    Calculate  the  change  in  absorbance,  )  A  =  A   -  A .  The
O T O
length of exposure should be sufficient to ensure a change in absorbance of at least
0.5.
Alternative packaging configurations may be used if appropriately validated.  Alternative
validated chemical actinometers may be used.
9 Note 1:  Shape and Dimensions (See Japanese Industry Standard (JIS) R3512 (1974) for
ampoule specifications)
10 V. GLOSSARY
! Immediate (primary) pack is that constituent of the packaging that is in direct contact
with the drug substance or drug product, and includes any appropriate label.
! Marketing pack is the combination of immediate pack and other secondary packaging
such as a carton.
! Forced degradation testing studies are those undertaken to degrade the sample
deliberately.  These studies, which may be undertaken in the development phase normally
on the drug substances, are used to evaluate the overall photosensitivity of the material for
method development purposes and/or degradation pathway elucidation.
! Confirmatory studies are those undertaken to establish photostability characteristics
under standardized conditions.  These studies are used to identify precautionary measures
needed in manufacturing or formulation and whether light-resistant packaging and/or
special labeling is needed to mitigate exposure to light.  For the confirmatory studies, the
batch(es) should be selected according to batch selection for long-term and accelerated
testing which is described in the parent guideline.
VI. REFERENCES
Drew, H.D., J.F. Brower, W.E. Juhl, and L.K. Thornton, "Quinine Photochemistry:  A
Proposed Chemical Actinometer System to Monitor UV-A Exposure in Photostability Studies of
Pharmaceutical Drug Substances and Drug Products," Pharmacopeial Forum, 24(3):6334, 1998.
Drew, H.D., L.K. Thornton, W.E. Juhl, and J.F. Brower, "An FDA/PhRMA
Interlaboratory Study of the International Conference on Harmonization's Proposed Photostability
Testing Procedures and Guidelines," Pharmacopeial Forum, 24(3):6317, 1998.
Sager, N., R.G. Baum, R.J. Wolters, and T. Layloff, "Photostability Testing of
Pharmaceutical Products," Pharmacopeial Forum, 24(3):6331, 1998.
Yoshioka, S., et al., "Quinine Actinometry as a Method for Calibrating Ultraviolet
Radiation Intensity in Light-Stability Testing of Pharmaceuticals," Drug Development and
Industrial Pharmacy, 20(13):2049-2062, 1994.
11