Stability studies

1. STABILITY STUDIES
……… A measure of how a pharmaceutical product
maintains its quality attributes over time
Dr. Gajanan S. Sanap M.Pharm.,Ph.D
Department of Pharmaceutics
Ideal College of Pharmacy and Research
Kalyan 421- 306

2. STABILITY –
The capacity of a drug or product to remain within established
specifications of identity , quality, purity in a specific period of time.
OR
The capacity or the capability of a particular formulation in a specific
container to remain with in particular chemical , microbiological ,
therapeutically , and toxicological specifications.
OR
USP defines stability of pharmaceutical product as , “extent to which a
product retains with in specified limits and throughout its period of
storage and use ( i.e. shelf life).

3. Stability testing is used to:
 Provide evidence as to how the quality of the drug product varies with
time.
 Establish shelf life for the drug product.
 Determine recommended storage conditions.
 Determine container closure system suitability.
Why Stability studies are necessary ?
 Chemical degradation of the product leads to lowering of the concentration
of the drug in the dosage form.
 Toxic products may be formed , due to chemical degradation of the active
ingredient.
Advantages of Stability studies
 Assurance to the patient Economic considerations Legal requirement

4.  OBJECTIVES
1. To determine maximum expiration date/ shelf life.
2. To provide better storage condition.
3. To determine the packaging components.
4. To gather information during preformulation stage to
produce a stable product.

5. Study Storage condition Minimum time
period covered by
data at submission
Long Term
(Ambient)
25º C ± 2º C
60%RH ± 5%
12 months
Intermediate
(controlled)
30º C ± 2º C
60%RH ± 5%
6 months
Accelerated 40º C ± 2º C
75%RH ± 5%
6 months

6. Kinetics
Kinetics Motion or
movement
Velocity, rate or
rate of change
Kinetics deals with the study of the rate at which processes
occur and mechanism of chemical reactions

7. It involves the study of rate of change and the way in which this rate is
influenced by the concentration of reactants, products, and other
chemical species that may be present, and by factors such as solvents,
pressure, and temperature.
Kinetics applies to:
Stability
Incompatibility,
Dissolution,
Absorption,
Distribution
Drug action at molecular level
Elimination processes

8. WHY DO WE STUDY ABOUT KINETICS?
It gives an in light into the mechanism of changes involved
Allows a prediction of the degree of change that will occur
after a given time has elapsed.

9. DRUG STABILITY
• The resistance of the drug to the various chemical, physical, and
microbiological reactions that may change the original properties of
the preparations during transport, storage and use.
• Quantitatively it is expressed as shelf life.
Shelf life
 is the time during which the medicinal product is predicted to
remain fit for its intended use under specified conditions of storage.
 It is the time from manufacture or preparation until the original
potency or content of the active ingredient has been reduced by 10%
[t10 or t90] which is the limit of chemical degradation

10. WHY DO WE STUDY ABOUT DRUG STABILITY?
Safety of the patient [toxic products or less potent product]
Legal requirements with identity, strength, purity and quality
To prevent economic repercussions.

11. RATES AND ORDERS OF REACTIONS
RATES
• the speed or velocity of a reaction with which a reactant or
reactants undergoes a change.
• It is determined by the change in the concentration of the
reactants or products as a function of time.
• The rate may be determined by the slowest or rate determining
step.
kc
n
Rate
dt
dc


12. ORDERS OF REACTIONS
the number of concentrations that determine rate.
the way in which the concentration of the reactant influences
the rate.
Law of mass action
 The rate of a reaction is proportional to the molar concentrations of the reactants each raised to
power equal to the number of molecules undergoing reaction.
a A + b B Product
Rate α [A]a .[B]b
Rate = K [A]a .[B]b
Order of reaction = sum of exponents
Order of A = a and B = b
Then Overall order = a + b

13. Example:
The reaction of acetic anhydride with ethyl
alcohol to form ethyl acetate and water
(CH3 CO)2 + 2 C2H5OH 2 CH3 CO2 C2H5 + H2O
Rate = K [(CH3 CO)2 O] . [C2H5OH]2
Order for (CH3 CO)2 O is 1st order
Order for [C2H5OH]2 is 2nd order
Overall order of reaction is 3rd Order

14. ZERO ORDER REACTIONS
rate is constant and is independent of the concentration of
any of the reactants.
A constant rate of drug release from a dosage form is highly
desirable.
Equation for zero order:

15. Equation for zero order:
a [A] k Product (P)
Rate = - dc/dt = K [c]0
- dc/dt = k dc = - k dt
co = Initial concentration
ct = Concentration at time t
 
t
t
c
c
kdtdc
t
00
C – C0 = -kt

16. Units of the rate constant K
c = co – Kt
K = co – c /t
K = Concentration / time
= mole / liter . second
= M. sec-1
C
t

17. Determination of t1/2
Let c = co /2 and t1/2 = t
substitute in equation;
c = co – k t
Note: Rate constant (k) and t1/2 depend on co
Determination of t0.9
Let c = 0.9 co and t= t0.9
substitute in equation;
c = co –k t
t1/2 = co / 2K
t90% = t0.9 = 0.1 co / k

18. Examples
• Drug X degrades by a zero-order process with a rate constant
of 0.05 mg ml1 year−1 at room temperature. If a 1%
weight/volume (w/v) solution is prepared and stored at room
temperature:
1. What concentration will remain after 18 months?
2. What is the half-life of the drug?

19. Answer
1. C0 = 1% w/v = 10 mg/ml; t =18 months = 1.5 year; k0 = 0.05
mg ml−1 year−1
C = C0 – k0t = 10 – (0.05 × 1.5) = 9.93 mg/ml
2. t1/2 = 0.5C0/k0 = (0.5 × 10)/0.05 = 100 years

20. FIRST ORDER REACTION
The most common pharmaceutical reactions
e.g; drug absorption & drug degradation
The reaction rate of change is proportional to drug
concentration.

21. - dc/dt = kc1 = kc
- dc/c = kdt
 

t
t
t
c
dtk
c
dc
00
ktcc o lnln
303.2
loglog 0
kt
cc 

22. C = co e –kt
Difficult to determine slope
lnc = lnco – kt
Slope = c1 – c2 / t1 – t2
Slope = -k
lnco
Log co
Log c = log co – kt / 2.303
Slope = c1 – c2 / t1 – t2
Slope = -k / 2.303
Or use semi log paper
C Lnc
Logc
t t
t

23. Determination of t1/2
Let t = t1/2 and C = C0 /2
substitute in ln C = ln C0 – Kt
t1/2 = ln 2/ K = 0.693 / K
K units = 0.693 / t1/2 = time-1
Determination of t0.9
Let t = t0.9 c = 0.9 Co
substitute in ln c = ln co – Kt
t0.9 = 0.105 / K and K = 0.105/ t0.9
t1/2 = 0.693 / K
t0.9 = 0.105 / K

24. Examples
1 Ten (10) ml aqueous solutions of drug A (10% w/v) and drug B
(25% w/v) are stored in two identical test tubes under
identical storage conditions at 37°C for 3 months. If both
drugs degrade by first-order, which drug will retain the highest
percentage of initial concentration?
(a) Drug A
(b) Drug B
(c) They will be the same.
2. The concentration of drug X in aqueous solution drops by 10%
per month when stored at room temperature. If the
degradation occurs by first order, what concentration will
remain if a 5 mg/ml solution of the drug is stored under the
same conditions for 3 months?

25. 3. A 5 gm/100 ml solution of drug X is stored in a closed test tube
at 25°C. If the rate of degradation of the drug is 0.05 day−1,
calculate the time required for the initial concentration to
drop to (a) 50% (half-life) and (b) 90% (shelf-life) of its initial
value.
4. A 5 gm/100 ml solution of drug X is stored in a closed test tube
at 25°C. If the rate of degradation of the drug is 0.05 day−1,
calculate the time for the drug concentration to degrade to
2.5 mg/ml.

26. PSEUDO ORDER REACTIONS
• For some reactions, the rate of the reaction may be
independent of the concentration of one or more of the
reacting species over a wide range of reactions.
• These may occur under the following conditions:
One or more of the reactants enters into the rate equation
in great excess compared to others;
One of the reactant is catalyst;
One or more of the reactants is constantly replenished
during the course of reaction

27. SECOND ORDER REACTION
Rate depends on the product of two concentration terms.
When you have two components reacting with each other or
one component reacting with itself.
Example: 2HI = H2 + I2 , here the reaction is not simply a
matter of an HI molecule falling apart, but relies on the
collision of two HI molecules.
The rate of reaction from the law of mass action is given by:
Rate = dc/dt = k[HI][HI] = k[HI]2

28. dc/dt = -kc2
dc/c2 = -kdt
 

t
t
c
c
dtk
c
dc
0
2
0
kt
cc

0
11
2nd Order reaction

29. 2nd order graph
Units of K:
1/C = 1/Co + Kt
K = (1/C - 1/Co) / t
K = M-1. sec -1
i.e, K is dependent on initial drug concentration.
Derive equation for t1/2 and shelf life
Half life: t1/2 = 1 / KCo
Shelf life: t0.9 = 0.11 / KCo

30. DETERMINATION OF ORDER AND RATE CONSTANTS
1. Substitution method [data plotting method]
• Data accumulated in experimental kinetic study may be
substituted in the integrated form of the equation that
describes the various reaction orders and observing which
plot is a straight line.
• Accordingly, plot of:
Concentration against time …….. zero order reaction [if
straight line]
ln concentration against time ……. First order reaction [if
straight line]
1/concentration against time …….. second order reaction
[if straight line].

31. 2.Half-life method
• This method is based on the relationship between the initial
concentration of the reactant, the half life, and the reaction
order.
• For zero-order reactions, t1/2 increases with increasing
concentration, whereas for first-order reactions, t1/2 does not
change with change in concentration

32. DEGRADATIVE PATHWAYS
Degradation of active drug leads to lowering of quantity of the therapeutic
agent in the dosage form.
 It may not be extensive , a toxic product formation may take place due to
decomposition instability of drug product can lead to a decrease in its
bioavailability .
Changes in physical appearance of given dosage form may take place.
Degradation may increase or may decrease the potency of drug.
Sometimes active drug may retain its potency , but excipients like –
antimicrobial , preservatives , solubilizers , emulsifying or suspending agent
may degrade , lead to compromising the integrity of drug product.
EXAMPLE :
 Drugs like 5-fluorouracil , carbamazipine , digioxin and theophylline have
narrow therapeutic indices these needs to be carefully treated in patient so
that plasma levels are neither too high as to be toxic nor too low as to be
ineffective
 The antimicrobial chloroquine can produce toxic reactions that are attribute
to the photochemical degradation of the substance.

33. DEGRADATION MAY BE OF TWO TYPES
 PHYSICAL DEGRADATION
 CHEMICAL DEGRADATION
1. OXIDATION
2. DECARBOXYLATION
3. PHOTOLYSIS
4. RACEMIZATION
5. HYDROLYSIS
 PHYSICAL DEGRADATION
The physical stability properties includes appearance, palatability ,uniformity
,dissolution and suspend ability are retained . Maintained throughout the shelf life
of the drug.
It includes following :
Loss of water
loss of volatile oil
Water Absorbance
Polymorphism
Color change

34. Physical degradation includes following :
LOSS OF VOLATILE CONTENT: Volatile compounds used such as
Alcohol ether , camphor oils , etc . Try to escape from the formulation
leads to degradation of formulation.
Example : nitroglycerine from drugs evaporate.
LOSS OF WATER : Water loss from liquid preparation (o/w emulsion)
leads to changes in stability .It causes crystallization of drug product .which
may lead to increase in potency , and decrease in weight.
Example : water evaporates from Na2SO4 .BORAX.
 WATER ABSORBANCE : pharmaceutical formulations which are
hygroscopic in nature absorb the water from its external environment leads
to degradation .
Example : gelatin capsule , deliquescent salts like –Cacl3 , Potassium
citrate.
POLYMORPHISM: A stable crystal form is effected (it may loosen)
leads to the formation of polymorph and cause instability in formulation.
This may lead to alteration in solubility , dissolution of drug
COLOR CHANGE: Loss or development of color may occur . (due to
change in PH , use of reducing agent , exposure to light )

35. Physical Stability
Physical stability implies that:
 The formulation is totally unchanged throughout its shelf
life and has not suffered any changes by way of appearance,
organoleptic properties, hardness, brittleness, particle size
etc.
 It is significant as it affects:
1.pharmaceutical elegance
2.drug content uniformity
3.drug release rate.

36. Physical Stability
Formulation Likely physical
instability problems
Effects
Oral solutions 1- Loss of flavor
2- Change in taste
3- Presence of off
flavors due to
interaction with plastic
bottle
4- Loss of dye
5- Precipitation
6- discoloration
Change in smell
or feel or taste

37. Formulation Likely physical
instability problems
Effects
Parenteral
solutions
1. Discoloration due to
photo chemical
reaction or oxidation
2. Presence of precipitate
due to interaction
with container or
stopper
3. Presence of “whiskers”
4. Clouds due to:
(i) Chemical changes
(ii) The original
preparation of a
supersaturated
solution
Change in
appearance and in
bio-availability

38. Physical stability
Formulation Likely physical
instability
problems
Effects
Suspensions 1- settling
2- caking
3- crystal
growth
1-Loss of drug
content
uniformity in
different doses
from the bottle
2- loss of
elegance.

39. Physical stability
Formulation Likely physical
instability
problems
Effects
Emulsions 1- Creaming
2- coalescence
1- Loss of drug
content
uniformity in
different doses
from the bottle
2- loss of
elegance

40. Physical stability

41. Physical stability
Formulation Likely physical
instability
problems
Effects
Semisolids
(Ointments and
suppositories)
1. Changes in:
a) Particle size
b) Consistency
2. Caking or
coalescence
3. Bleeding
1-Loss of drug
content
uniformity
2- loss of
elegance
3-change in
drug release
rate.

42. Physical stability
Formulation Likely physical
instability problems
Effects
Tablets Change in:
a) Disintegration
time
b) Dissolution profile
c) Hardness
d) Appearance (soft
and ugly or
become very
hard)
Change in
drug release

43. CHEMICAL DEGRADATION
Chemical degradation of a dosage form occurs through several pathways
like –hydrolysis , oxidation , decarboxylation , photolysis , racemization.
which may lead to lowering of therapeutic agent in the dosage form,
formation of toxic product , decreased bioavailability etc.
1. HYDROLYSIS
 Most important in systems containing water such as emulsion , suspension ,
solutions , etc.
 Also for drugs which are affected by moisture (water vapor) from
atmosphere.
 It is usually catalysed by hydrogen ion(acid) or hydroxyl ion(base).
 In this active drug is decomposed with solvent.
 Usually solvent is water some time reaction may involve pharmaceutical
co solvents such as ethyl alcohol or poly ethylene glycol
 Main classes of drugs that undergo hydrolysis are the ESTERS ,AMIDE
,ALKALI, ACID.

44. Cont…
 ESTER HYDROLYSIS involve acyl – acid cleavage.
 Example of drugs: aspirin ,atropine , physostigmine , procaine..
 R .COOR (ester) + H2O  RCOOH (acid) + HOR(alcohol)
 AMIDE HYDROLYSIS is more stable than ester , susceptible to specific and
general acid base hydrolysis. It involves cleavage of amide linkage to give an
amine instead of alcohol as in case of esters.
 Example of drugs : chloramphenicol , barbiturates .
 RCONHR(amide) + H2 O  RCOOH + NH2 R(AMINE)

45. Some functional groups subject to
Hydrolysis
Drug type Examples
Esters Aspirin, alkaloids
Dexmethasne sodium
phosphate
Nitroglycerin
Lactones Pilocarpine
Spironolactone
Amides Chloramphenicol
Imides Glutethimide
Malonic ureas Barbiturates

46. PROTECTION AGAINST OXIDATION
 Avoiding contact with moisture at time of manufacture.
 Packaging in suitable moisture resistant packs such as strip packs and storage in
controlled humidity and temperature.
 In liquid dosage form since , hydrolysis is acid or base catalyzed , an optimum
PH for max stability should be selected and the formulation should be stabilized
at this PH by inclusion of proper buffering agents.
 Hydrolysis of certain drugs such as benzocaine and procaine can be decreased
by the addition of specific complexing agent like caffeine to the drug solutions .
 Hydrolysis susceptible drugs such as penicillin and derivatives can be prevented
by formulating them in the dry powder form for reconstitution or dispersible
tablets instead of a liquid dosage form such as solutions or suspensions.

47. 2. OXIDATION
 Oxidation is controlled by environment i.e, light ,trace elements , oxygen and
oxidizing agent .
 Occurs when exposed to atmospheric oxygen.
 Either the addition of oxygen or removal of hydrogen .
 Oxidation is the loss of electrons while reduction is the gain of electrons.
AUTOXIDATION
 The reaction between the compounds and molecular oxygen is required for
initiating the chain reaction is called autoxidation .
 Free radicals produced during initial reaction are highly reactive and further
catalyze the reaction produced additional free radicals and causing a chain
reaction.

48.  Heavy metals such as copper , iron , cobalt , and nickel have been known to
catalyze the oxidative degradation .Heat and light further influence the kinetics
of oxidative degradation processes.
STEPS INVOLVED OXIDATION REACTION
 INITIATION : Formation of free radicals is taken place .
R--H  R’ + [H’}
 PROPOGATION : here the free radical is regenerated and react with more oxygen .
R’ + O2  R’—O2
R’O2 + RH  ROOH + R’
 HYDROPEROXIDE DECOMPOSITION
ROOH  RO’ + OH’
 TERMINATION : free radicals react with each other resulting in inactive products.
R’--O2 + X  Inactive product
RO2 + RO2  Inactive product
EXAMPLE OF DRUGS DECOMPOSED BY OXIDATION PATHWAYS
Archis oil , clove oil , ethyl oleate ,Heparin , Ascorbic acid , Morphine ,Vitamin A , Vitamin
B12 , etc.

49. PROTECTION AGAINST OXIDATION
USE OF ANTIOXIDANTS : antioxidants are Mainly of 3 types :
1. The first group probably inhibits the oxidation by reacting with free radicals.
Example – tocopheral , butylated hydroxyl anisole (BHA) , butylated hydroxyl
toluene's (BHT). Concentration 0.001 – 0.1%.
2. The second group comprising the reducing agents , have a lower redox potential
than the drug or other substance that they should protect and are therefore more
readily oxidized.
Example –ascorbic acid and iso ascorbic acid , potassium or sodium salts of
metabisulfite.
3. The third group, little antioxidant effect themselelf but enhance the action of true
antioxidant .example
Example -- Citric acid , tartaric acid , disodium edetate and lecithin .
USE OF CHELATING AGENT
when heavy metals catalyze oxidation .
Example -- EDTA , citric acid , tartaric acid form complexes.

50. 3. PHOTOLYSIS
 Exposure to light cause substantial degradation of drug molecule.
• When molecules are exposed to electromagnetic radiation they absorb light
(photons) at characteristic wavelength which cause increase in energy which
can :
 Cause decomposition.
 Retained or transferred.
 Be converted to heat .
 Result in light emission at a new wavelength (fluorescence ,
phosphorescence).
• Natural sun light lies in wavelength range (290– 780nm) of which only higher
energy (UV) range (290 --320) cause photo degradation of drugs.
 `

51.  Example of phototoxic drugs:
Furosemide , acetazolamide , cynocobalamine .
 EXAMPLE
Sodium nitropruside in aqueous solution (which is administered by IV infusion
for management of acute hypertension ).
 If protected from light it is stable to at least 1yr.
 If exposed to normal room light it has a shelf life of 4 hrs.
PROTECTION
 Use of amber colored bottles .
 Storing the product in dark , packaging in cartons also act as physical barrier to
light.
 Coating of tablets with polymer films.

52. Accelerated Stability StudiesAccelerated Stability Studies
Stability study to predict the shelf life of the product, by accelerating
the rate of decomposition, preferably by increasing the temperature of
reaction conditions.
With the advancement in branch of kinetics, shelf life of a dosage form
can be predicted within months based on accelerated stability reports
Preparations are subjected to high stresses during stability testing.
Common high stresses include :
 Temperature
 Humidity
 Light

53. It is defined as the time required for the concentration of the reactant to reduce to
90% of its initial concentration .Represented as t90 and the units of time /conc.
t90 = (a-0.9a) = 0.1 a
ko ko
Where , a = initial concentration .
ko = specific rate constant for zero order reaction.
(the time from the date of manufacture and packaging of the formulation until its
chemical or therapeutic activity is maintained to a predetermined level of labeled
potency and ,
its physical characteristic have not changed appreciably or deleteriously ).

54. Arrhenius equation
It explains the effect of temperature on rate of a reaction.
According to Arrhenius, for every 10º rise in temperature, the speed
of reaction increases about 2-3 times.
k = A e -Ea / RT
Arrhenius factor
Energy of activation
Ideal gas constant
Log k = log A – Ea / 2.303 RT
Arrhenius factor is the frequency of molecular collisions occuring between
the molecules.

55. Estimation of k value
 The reaction is conducted at several temperatures.
 Concentration of reactants is determined.
 Appropriate graphs are drawn for the kinetic data.
 Data is processed for all the orders.
 The order of the reaction is identified.
 From the slopes of the lines, k values are calculated for all
temperatures.

56. Estimation of energy of activation
 A graph can be drawn by taking log k on y-axis and reciprocal
temperature (1/T) on x-axis.
 A straight line is obtained, the slope of the line is negative and the
magnitude is Ea / 2.303 R.
 The intercept corresponds to log A
 All the constants in the Arrhenius equation can be obtained from the
graph.
Activation energy is the minimum energy that a molecule should
possess so that the molecular collisions produce the product.

58.  The Preparation is stored at different elevated temperatures, to
accelerate the degradation
 Samples are withdrawn at different time intervals
 The Order of the reaction is determined by plotting the appropriate
function of concentration against time and linear relationship is
determined
 Straight line in a graph permits the estimation of k value from the slope
 Similarly graphs are drawn for different elevated temperatures.
 K value for each temperature are calculated.
 By using Arrhenius relationship, Log k values are plotted against
reciprocal of absolute temperature, energy of activation can be
calculated.
Steps involved in prediction of shelf life

59.  Extrapolate the straight line to room temperature (k25) or
refrigerated temperature and read the log k value on y-axis.
 Substitute the k value in the appropriate equation to get the shelf
life of the product.

60. Arrhenius plot for predicting the rate constant at ambient
temperature(25ºC).

61. Stability
investigation
Organoleptic and
physicochemical
stability
Photostability
Chemical stability
Dosage form
Solid
Semisolid
Liquid
All
Solid
Semisolid
Liquid
Storage condition
Storage in open
container until
equilibrium is reached at
25ºC/60%,30ºC/70%,
40ºC/75%
5ºC
≥ - 10ºC
5ºC -40ºC Temperature
cycle within 24 hrs
40ºC(content uniformity)
5ºC
≥ -10ºC
Xenon lamp
40ºC, 50ºC, 60ºC, 70ºC
30ºC, 40ºC, 50ºC
40ºC, 50ºC, 60ºC, 70ºC
Storage period
1-2 weeks
4 weeks
4 weeks
2 weeks
3 months
4 Weeks
4 weeks
48 hrs
3 months
3 months
3 months

62. LONG TERM STABILITY STUDIES :
According to WHO, long term stability testing during and beyond expected shelf life
under storage conditions in the intended market.
RECOMMENDED CONDITIONS FOR LONG TERM STABILITY
ACCELERATED STABILITY STUDIES:
In , general the accelerated stability conditions must be at least 15’C above the
actual storage temperature and appropriate relative humidity . Substances and
drugs products intended to be stored in a refrigerator . the accelerated stability
studies should be carried out at 25+/-2’c and 60+/-5% relative humidity.
STORAGE CONDITIONS
TEMPERATURE (‘C) RELATIVE HUMIDITY% MINIMUM TIME
25’C+/- 2’C 60 +/- 5% 12 MONTHS
30’C +/- 2’C 30+/- 5% 6 MONTHS
STORAGE CONDITIONS
TEMPERATURE (‘C) RELATIVE HUMIDITY% MINIMUM TIME
40’C +/- 2’C 75 +/-5% 6 MONTHS

63. Testing Frequency:
For Long term testing, during first year sampling should be done
every
three months, during second year, sampling should be done every six
months and after two years, sampling should be done once a year.
Accelerated testing should be done atleast six months and it
suggests
sampling points of 0, 3, 6 months.

64. Methods Of Accelerated Stability
Testing In Dosage forms
 Freeze Thaw test
 Centrifugal Test
 Shaking test
 Elevated Temperature test

65. Accelerated Stability Testing in Emulsions
An emulsion is stored at elevated temperature. This decreases viscosity of the
continuous phase. If the emulsion withstands this stress it is assumed to be
stable at normal conditions of storage.
Centrifugation Method:
Creaming and flocculation are slow processes.
Centrifugation accelerates rate of creaming and flocculation in emulsions.
The emulsion is subjected to different centrifugal speeds and separation of
phases is observed at different time periods.
Bad emulsion separates oil instantly.
Good emulsion does not exhibit detectable separation of oil phase until certain
time period.

66. Accelerated tests for Suspensions
Cake formation is accelerated by centrifugation.
High speed centrifugation is hence not preferred, low speed centrifugation
is used to study the physical stability.
A Freeze-Thaw cycling technique is one of the stress testing . This cycling
treatment promotes particle growth and has primary importance for
changes in absolute particle size, particle size distribution and
crystal habit.

67. Accelerated Tests for moisture absorption
In this method, products are placed in an environment of high relative
humidity and controlled temperature.
Their physical and chemical stabilities are assessed.
The results will indicate whether the product is susceptible to moisture
and also whether the container needs to provide a high degree of
protection.

68. Limitations
 Stability predictions based on Arrhenius equation are valid only
when the break down depends on temperature.
 The energy of activation obtained in the study should be between
10 to 30 kcal/mole.
 When degradation is due to
Microbial contamination
Photochemical reactions
 When the product looses its physical integrity at higher temperatures.
 When the order changes at elevated temperatures.
 In case of disperse systems, when temperature is elevated viscosity is
decreased and this may introduce errors in the prediction of stability.

69.  Describes regarding sampling times ,storage conditions&
specific test parameters for each dosage form.
The FDA & The expert working group of the ICH of technical
requirements for the registration of pharmaceuticals for
human use have published guidelines for conducting the
actual studies.

70. ICH Guidelines
• Quality Guidelines “Q” (chemical and pharmaceutical QA)
• Safety Guidelines “S” (in vitro and in vivo pre-clinical studies)
– covering Carcinogenicity Testing, Genotoxicity Testing,
Toxicokinetics and Pharmacokinetics ….. etc.
• Efficacy Guidelines “E” (clinical studies in human subject)
– Covering clinical safety, Dose Response Studies, Good
Clinical Practices, Clinical evaluation …. etc.
• Multidisciplinary Guidelines “M”
– Covering Medical Terminology, Electronic Standards for
Transmission of Regulatory Information …… etc.
– Important for Stability !
» Guideline M4: The Common Technical Document (CTD)

71. Stability Testing Q1
 Stability Testing in Climatic Zone I and II (Q1A)
 Photo stability Testing (Q1B)
 Stability Testing for New Dosage Forms (Q1C)
 Bracketing and Matrixing Designs (Q1D)
 Evaluation of Stability Data (Q1E)
 Stability Testing in Climatic Zones III and IV (Q1F)
Validation of Analytical Procedures (Q2)
Impurities (Q3)
 Impurities in New Drug Substances (Q3A)
 Impurities in New Drug Products (Q3B)
Pharmacopoeial Harmonization (Q4)
Biotechnological Products (Q5)
Specifications (Q6)
ICH – Q – Guidelines

72. DEFINITIONS
Shelf life (expiration dating period, conformance period)
Self life is the time period during which a drug product is expected to
remain within the approved specification for use, provided that it is
stored under the conditions defined on the container label.
Re-test period
The period of time during which the drug substance is expected to remain
within its specification and, therefore, can be used in the manufacture of a
given drug product, provided that the drug substance has been stored
under the defined conditions.

73. Formal stability studies
Long term and accelerated (and intermediate) studies undertaken on primary
and/or commitment batches according to a prescribed stability protocol to
establish or confirm the re-test period of an API or the shelf life of a FPP.
Stress testing – forced degradation (API)
Studies undertaken to elucidate the intrinsic stability of the API. Such testing
is part of the development strategy and is normally carried out under more
severe conditions than those used for accelerated testing.
Stress testing – forced degradation (FPP)
Studies undertaken to assess the effect of severe conditions on the FPP. Such
studies include photostability testing (see ICH Q1B) and compatibility testing
on APIs with each other in FDCs and API(s) with excipients during
formulation development.

74.  Primary batch (called also exhibit batch)
A batch of an API or FPP used in a formal stability study, from which stability
data are submitted in a registration application for the purpose of establishing a
re-test period or shelf life, respectively. A primary batch of an API should be at
least a pilot scale batch. For a FPP, two of the three batches should be at least pilot
scale batch, and the third batch a production batch.
 Commitment batches
Production batches of a drug substance or drug product for which the stability
studies are initiated or completed post approval through a commitment made in
the registration application.
 Pilot (scale) batch
A batch of an API or FPP manufactured by a procedure fully representative of
and simulating that to be applied to a full production scale batch. (For solid oral
dosage forms, a pilot scale is generally, at a minimum, one-tenth that of a full
production scale or 100,000 tablets or capsules, whichever is the larger.)
 Production (scale) batch
A batch of an API or FPP manufactured at production scale by using production
equipment in a production facility as specified in the application.

75.  Specification - Release
The combination of physical, chemical, biological, and microbiological tests
and acceptance criteria that determine the suitability of a drug product at the
time of its release.
 Specification - Shelf life
The combination of physical, chemical, biological, and microbiological tests
and acceptance criteria that determine the suitability of an API throughout
its re-test period, or that anFPP should meet throughout its shelf life.
 Mass balance
The process of adding together the assay value and levels of degradation
products to see how closely these add up to 100% of the initial value, with
due consideration of the margin of analytical error.

76. WORLDWIDE ZONES / TEMPERATURE AND
HUMIDITY CONDITIONS
Zone Mean kinetic
temperature
Yearly average
humidity (%RH)
Zone I ( Moderate) 21 ̊C 45
Zone II (Mediterranean) 25 ̊C 60
Zone III (Hot, dry) 30 ̊C 35
Zone IV (Very hot, moist) 30̊ C 70

77. COUNTRIES AND ZONES
Regions Zone I &II Zone III&IV
EUROPE All countries
AMERICA Argentina, Bolivia, Canada,
Mexico, US
Brazil, Columbia, Cuba,
Jamaica
ASIA Afghanistan, China, Iran,
Nepal, Turkey, Japan
Bahrain , Hong Kong, India,
Oman , Pakistan, Srilanka,
UAE
AFRICA Egypt, Algeria, South Africa,
Libya
Angola, Benin, Congo,
Uganda, Sudan, Somalia,
Senegal

78. Study Storage condition
Minimum time period covered
by data at submission
Long term 25°C ± 2°C / 60% ± 5% r.h or
30°C ± 2°C / 65% ± 5% r.h.
12 months
Intermediate 30°C ± 2°C / 65% ± 5% r.h. 6 months
Accelerated 40°C ± 2°C / 75% ± 5% r.h. 6 months
STORAGE IN A REFRIGERATOR
Study Storage condition Minimum time period covered
by data at submission
Long term 5°C ± 3°C 12 months
Accelerated 25°C ± 2°C / 60% ± 5% r.h. 6 months
STORAGE CONDITIONS FOR STABILITY STUDY
API/DRUG SUBSTANCES TO BE STOTRED AT AMBIENT TEMPERATURES
Study Storage condition Minimum time period
covered by data at
submission
Long term -20°C ± 5°C 12 months
STORAGE IN FREEZER

79. DRUG PRODUCTS - PACKAGED IN
SEMI-PERMEABLE CONTAINERS
Study Storage condition Minimum time period
covered by data at
submission
Long term 25°C ± 2°C / 40% ± 5% r.h. or
30°C ± 2°C / 35% ± 5% r.h.
12 months
Intermediate 30°C ± 2°C / 65% ± 5% r.h. 6 months
Accelerated 30°C ± 2°C / 65% ± 5% r.h. 6 months

81. The Stability Chambers are designed for an operating range of 4°C to
70°C Temperature only, 5°C to 60°C Temperature with Humidity.
These units employ a programmable controller to control the
temperature, defrost and humidity settings. The cabinets use an
evaporator coil, located on top of the cabinet as the heat-removing
source. Through the refrigeration process, heat is captured in the
evaporator, transferred to the condensing unit on top of the cabinet,
and expelled to the surrounding outside air. It is extremely important
to allow a four-inch clearance on the top, rear, and sides of the unit
for the refrigeration process to function properly.

82. STABILITY CABINETS:

83. STABILITY CABINETS:

84. Packaging And Stability
1.Glass
 Glass is resistant to chemical and
physical change and is the most commonly used material.
Limitations Overcome
1. Its alkaline surface use of Borosilicate glass
2. Ions may precipitate
insoluble crystals from the
glass
the use of buffers
3- Permits the transmission
of light which may accelerate
decomposition.
Amber coloured glass

85. Packing and Stability
2.PLASTICS
The problems with plastic are:
 Migration of the drug through the plastic into the
environment.
 Transfer of environmental moisture, oxygen, and other
elements into the pharmaceutical product.
 Leaching of container ingredients into the drug.
 Adsorption of the active drug or
excipients by the plastic.

86. Packing and Stability
3.Metals
 Various alloys and aluminum tubes may be utilized as
containers for emulsions, ointments, creams and pastes.
 Limitation: They may cause corrosion and precipitation in
the drug product.
 Overcome: Coating the tubes with polymers may reduce
these tendencies.

87. Packing and Stability
Rubber
 Rubber also has the problems of extraction of drug
ingredients and leaching of container ingredients.
 The pretreatment of rubber vial stoppers and closures with
water and steam reduces potential leaching.

88. Physical stability
Formulation Likely physical
instability
problems
Effects
Capsules Change in:
a) Appearance
b) Dissolution
c) Strength
Change in drug
release

89. Types of Stability Studies
1.Long-Term (Real-Time) Stability Testing
 Stability evaluation of the physical, chemical, biological
and microbiological characteristics of a drug product
 duration of the shelf life

90.  Packaging materials permeable to water vapor result in a
falsification of the results for semisolid and liquid dosage forms if
varying degrees of weight loss occur that leads to differences in the
active ingredient concentration or ion strength.
 The use of inert standard packaging materials that are impermeable
to water vapor is important precondition for stress tests that are
evaluated in terms of reaction kinetics, and on the results on which
stability predictions are to be tested.

91.  Solid dosage forms: 50-mL glass container with twist-off closure
polypropylene tube
 Semisolid dosage forms: Standard tube, small volumetric flask,
Aluminum tube, inert internal lacquering
 Liquid dosage forms: 25mL volumetric flask with ground-glass
stopper
 However, furture investigations for the selection of the final
packaging are necessary.

92.  On the basis of the results of the stress tests for solid dosage forms,
the sensitivity to moisture can be determined and suitable
packaging materials can be selected.
 As a rule, no interactions are to be expected.
 If the final packaging material has been selected and samples
packed in the final packaging material are available, the
investigation of photostability should be performed.
 Photostability :The samples with and without container are
irradiated with a Xenon lamp for 24 hours.

93.  Packaging: Aluminum tube internally lacquered, plastic tubes.
 Problems: Corrosion , permeation, sorption.
 Tests packaging material – dosage form:
To test for corrosion ,the filled metal tubes are stored horizontally
upright and inverted at 400C, for 3 months and are then
investigated.
 To test for permeation and sorption the filled plastic tubes are
stored for 3 months at 500C, 400C, 300C/70%.
 If the final packaging material has been selected, the investigations
on the photostability are performed.

94.  Packaging ampoule, injection vial with rubber stopper, glass bottle
or plastic bottle with screw closure.
 Problems: leakage.
 To test for permeation, and leakage, the finale formulation solution
is filled in the container, and for desorption placebo solution is
used.
 The samples are stored vertically and inverted under 500C, 400C,
300C/70% for up to 12 weeks.
 Tested intervals: 0, 1, 2, 3 months.
 If the final packaging material has been selected the investigations
on the photostability are performed.

95. TABLET
 Stable tablets retain their original size ,shape , weight ,roughness ,colour variation ,
cracking under normal handling and storage conditions throughout their shelf life.
• FRIABILITY TEST : studies revel the physical instability if any in tablet.
Maximum weight loss should not be more than 1%.
• HARDNESS TEST : shows resistance to crushing.
• COLOR STABILITY : by colorimeter , reflectometer with heat , sunlight and intense
artificial light.
 Uniformity of weight , odor , texture , drug and moisture content , humidity effects
are also Studied during a tablet test.

96. GELATINE CAPSULE
Gelatin capsules are found to be stable in dry
conditions but they rapidly reach equilibrium with
the atmospheric conditions under they are stored.
This shows gelatin capsules are largely effected by
temperature and humidity and susceptibility to
microbial degradation .
 soft gelatin capsule have Relative Humidity 20 to
30% at 21 to 24’C.
 hard gelatin capsule contain 13 to 16% moisture.
Humidity - capsule shell softens and becomes
sticky.
Dried- capsule shell becomes brittle and crack.
Hard gelatin capsule are tested for Brittleness ,
dissolution , water content and level of microbial
contamination.

97. EMULSIONS
Tested for phase separation , PH , viscosity , level of microbial
contamination , and distribution of dispersed globules.
ORAL SOLUTIONS AND SUSPENSIONS
Formation of precipitate , clarity for solutions , PH , viscosity ,
microbial contamination.
Additionally for suspensions , redispersibility , rheological
properties ,mean size and distribution of particles should be
considered .
NASAL SPRAYS : solution and suspensions
Clarity (for solution) , level of microbial contamination , PH ,
particulate matter , unit spray medication , content uniformity
, droplet and/or particle size distribution , weight loss , pump
delivery.
Microscopic evaluation ,(for suspension) , foreign particulate
matter and extractable/ leachable from components of the
container , closure and pump.
TOPICAL , OPTHALMIC AND OTIC PREPRATION
Included in this broad category are ointments ,creams , lotions
,paste , gel , solutions ,eye drops and cutaneous sprays.

98. TOPICAL
preparations should be evaluated for clarity , homogeneity , PH ,
resuspendibility for lotions , consistency , viscosity , particle size
distribution ,level of microbial contamination / sterility and weight
loss
FOR OPTHALMIC OR OTIC PREPRATION
Should include the following additional attributes : sterility
,particulate matter ,and extractable.
SUPPOSITORIES
Softening range , dissolution (at 37’C)
PARENTERALS
Color , clarity (for solutions) , particulate matter , PH, sterility ,
pyogen / endotoxins .
Stability studies for powders for injection solution ,include color
monitoring , reconstitution time and water content ,to be performed
at regular intervals .