stability studies

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 PharmaceuticsIdeal College of Pharmacy and Research

Kalyan 421- 306

INTRODUCTIONSTABILITY –

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).

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

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.

Stability Protocol 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

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

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

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.

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

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.

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.

kcnRatedtdc

ORDERS OF REACTIONSthe 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

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

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:

Equation for zero order:

a [A] k Product (P)Rate = - dc/dt = K [c]0

- dc/dt = k dc = - k dt

co = Initial concentrationct = Concentration at time t

t

t

c

c

kdtdct

00

C – C0 = -kt

Units of the rate constant Kc = co – KtK = co – c /t

K = Concentration / time = mole / liter . second = M. sec-1

C

t

Determination of t1/2

Let c = co /2 and t1/2 = tsubstitute 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

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?

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

FIRST ORDER REACTION

The most common pharmaceutical reactions e.g; drug absorption & drug degradation

The reaction rate of change is proportional to drug concentration.

- dc/dt = kc1 = kc - dc/c = kdt

t

t

t

c

dtkcdc

00

ktcc o lnln

303.2loglog 0

ktcc

C = co e –kt

Difficult to determine slope lnc = lnco – ktSlope = c1 – c2 / t1 – t2

Slope = -k

lnco

Log coLog c = log co – kt / 2.303Slope = c1 – c2 / t1 – t2

Slope = -k / 2.303

Or use semi log paper

C Lnc

Logc

t t

t

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

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?

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.

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

SECOND ORDER REACTIONRate 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

dc/dt = -kc2

dc/c2 = -kdt

t

t

c

c

dtkcdc

02

0

ktcc

0

11

2nd Order reaction

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 / KCoShelf life: t0.9 = 0.11 / KCo

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].

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

DEGRADATIVE PATHWAYSDegradation 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.

DEGRADATION MAY BE OF TWO TYPES PHYSICAL DEGRADATION CHEMICAL DEGRADATION

1. OXIDATION2. DECARBOXYLATION 3. PHOTOLYSIS4. RACEMIZATION 5. HYDROLYSIS

PHYSICAL DEGRADATIONThe 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 waterloss of volatile oilWater Absorbance Polymorphism Color change

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 )

Physical StabilityPhysical 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.

Physical StabilityFormulation Likely physical

instability problemsEffects

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

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

Physical stabilityFormulation Likely physical

instability problems

Effects

Suspensions 1- settling2- caking3- crystal growth

1-Loss of drug content uniformity in different doses from the bottle

2- loss of elegance.



Effects

Emulsions 1- Creaming 2- coalescence

1- Loss of drug content uniformity in different doses from the bottle

2- loss of elegance

Physical stability



Effects

Semisolids (Ointments and suppositories)

1. Changes in:a) Particle sizeb) Consistency

2. Caking or coalescence

3. Bleeding

1-Loss of drug content uniformity

2- loss of elegance 3-change in drug release rate.



Effects

Tablets Change in:a) Disintegration

timeb) Dissolution profilec) Hardness d) Appearance (soft

and ugly or become very hard)

Change in drug release

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.

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)

Some functional groups subject to Hydrolysis

Drug type ExamplesEsters Aspirin, alkaloids

Dexmethasne sodium phosphateNitroglycerin

Lactones PilocarpineSpironolactone

Amides Chloramphenicol

Imides GlutethimideMalonic ureas

Barbiturates

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.

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.

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 productRO2 + RO2 Inactive product

EXAMPLE OF DRUGS DECOMPOSED BY OXIDATION PATHWAYSArchis oil , clove oil , ethyl oleate ,Heparin , Ascorbic acid , Morphine ,Vitamin A , Vitamin

B12 , etc.

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.

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.

`

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.

Accelerated Stability Studies Accelerated 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 reportsPreparations are subjected to high stresses during stability testing. Common high stresses include : Temperature Humidity Light

SHELF LIFE

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 koWhere , 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 ).

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.

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.

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.

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

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.

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

Overview of storage conditions and storage period for solid, semisolid, and liquid dosage formsStability investigation

Organoleptic and physicochemical stability

Photostability

Chemical stability

Dosage form

Solid

Semisolid

Liquid

All

SolidSemisolidLiquid

Storage condition

Storage in open container until equilibrium is reached at 25ºC/60%,30ºC/70%,40ºC/75%

5ºC≥ - 10ºC5ºC -40ºC Temperature cycle within 24 hrs 40ºC(content uniformity)

5ºC≥ -10ºC

Xenon lamp

40ºC, 50ºC, 60ºC, 70ºC30ºC, 40ºC, 50ºC40ºC, 50ºC, 60ºC, 70ºC

Storage period

1-2 weeks

4 weeks4 weeks2 weeks3 months

4 Weeks4 weeks

48 hrs3 months3 months3 months

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 TIME25’C+/- 2’C 60 +/- 5% 12 MONTHS30’C +/- 2’C 30+/- 5% 6 MONTHS

STORAGE CONDITIONSTEMPERATURE (‘C) RELATIVE HUMIDITY% MINIMUM TIME40’C +/- 2’C 75 +/-5% 6 MONTHS

Testing Frequency:For Long term testing, during first year sampling should be done everythree 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.

Methods Of Accelerated Stability Testing In Dosage

forms

Freeze Thaw test Centrifugal Test Shaking test Elevated Temperature test

Accelerated Stability Testing in EmulsionsAn 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.

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.

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.

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.

ICH guidelines: 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.

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)

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

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.

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.

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.

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.

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

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

Study

Storage condition

Minimum time period covered by data at submission

Long term 25°C ± 2°C / 60% ± 5% r.h or30°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


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

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. or30°C ± 2°C / 35% ± 5% r.h.

12 months

Intermediate 30°C ± 2°C / 65% ± 5% r.h. 6 months


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.

STABILITY CABINETS:

Packaging And Stability1.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

Packing and Stability2.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.

Packing and Stability3.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.

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.



Effects

Capsules Change in:a) Appearanceb) Dissolution c) Strength

Change in drug release

Types of Stability Studies1.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

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.

Packaging material:in selecting packaging material, the following has to be considerd

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.

Most of the stress tests are carried out in standard packaging material.The following standard packaging materials are used:

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.

Selection of packaging material for solid dosage forms.

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.

Selection of packaging material for semisolid dosage forms.

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.

Selection of packaging material for liquid dosage forms

STABILITY STUDIES FOR PHARMACEUTICAL PRODUCTSTABLET

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.

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.

EMULSIONS Tested for phase separation , PH , viscosity , level of microbial contamination , and distribution of dispersed globules.ORAL SOLUTIONS AND SUSPENSIONSFormation 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 PREPRATIONIncluded in this broad category are ointments ,creams , lotions ,paste , gel , solutions ,eye drops and cutaneous sprays.

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.

SUPPOSITORIESSoftening range , dissolution (at 37’C)

PARENTERALSColor , 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 .

stability studies

Health & Medicine