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Stability Of Drugs:Stability Programmes And Stability Testing

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Contents

Introduction

Stability Of Drugs

Introduction
Physical Stability
Chemical Stability
Microbiological Stability
Mechanisms
Photolysis
Rate Kinetics
Effect Of Temperature/pH
Factors Affecting
Packaging And Stability
Stability Programmes
Author

When a manufacturer plans to design, manufacture and market a drug product it is his responsibility to provide to the regulatory authorities assurance that the drug product meets with all the labelled claims and is stable in all senses till the expiry date is over. This responsibility implies that he/she undertake stability testing studies in a systematic way right from the Phase-I studies level. Upto the seventies these studies were undertaken by different companies in different manner. But today ICH guidelines help the manufacturers adopt a stability programme that is suitable for them. The final draft the ICH Harmoised Tripartite Guideline “Stability Testing of New Drug Substances and Products was issued by the International Conference on Harmonization (ICH) Expert Working Group of the ICH on technical requirements for the registration of pharmaceuticals for human use in October 1993. J.T. Cartensen in his book “Drug Stability, Principles and Practices” discussed these guidelines in great detail.


Stability programme for a new drug

These guidelines divide the world into four zones and specify the temperature and relative humidity conditions to be maintained by each zone for stability studies. For example, if a manufacturer plans to sell his products in Zone III he has to submit stability data of his batches of products maintained at the temperature and relative humidity suggested by ICH for Zone III.

I will introduce the spirit and the text of the guidelines to you in a very brief manner.

Stability testing is done in five different occasion when an NDA is being contemplated.

1. Preformulation and compatibility

2. Preclinical formulation

3. Clinical and NDA formulation

4. Commitment and product monitoring

5. Post NDA change of formulation


Preformulation and compatibility

In the early stage of drug designing studies are done to find out what sort of decomposition is possible, what is the mechanism, sensitivity to moisture and oxygen interaction probabilities (compatibilities) optimum pH and polymorphic information. Drug excipient interactions physical as well as chemical are extensively studied.

Preclinical formulation

Keeping the data from the preformulation studies in mind formulations are designed and manufactured for use in Phase-I trails. More than the one or two formulations being used in Phase-I studies are manufactured and started on stability studies. This is because even a supposedly stable formulation may while in Phase-I use fail with respect to some stability issue, then you must have something to fall back upon.

Clinical formulation

When a product has passed Phase-I, its dosage level, interactions and stability profile are known to some degree and armed with this knowledge the “Clinical manufacturing group” of the company manufactures several batches of the product and keeps some products from every batch for stability. The required stability aspects of clinical are simply to ascertain that each batch is within specifications during the length of the trail.


Late Clinical and First Pilot Batch

The ICH stability guidelines require that three substantial batches, made in the same type production equipment intended for the final product, be made and that at least 12 months stability be in place at the time of NDA submittal.

Marketed product stability

At the time the NDA is filed, the large clinical and scate-up batches are only about a year old, and the stability data on them is not yet complete. So at this time, the company asks for an expiry date based on extrapolation of the existing stability data. The FDI will take all facts into consideration and grant an expiry date based on a commitment form the company that the company will continue to do stability studies on different batches.

The storage requirements and the sampling times are very clearly specified by the ICH guidelines.

A Brief History of ICH

Prior to 1960s there were not many controls over introduction of new drugs and also over the assurance of the quality by the manufacturer over his established drug products. Some stray tragic incidents in some countries like USA and India triggered the introduction of exacting drug laws to ensure the quality, safety and efficacy of the drug. Around 1970s the pharmaceutical industry started getting global but the registration of medicines remained a national responsibility. Although the laws of all the countries were based on the same fundamental obligations to evaluate the quality, safety and efficacy the detailed technical requirements differed from country to country. So the companies had to duplicate many time consuming and expensive test procedures, in order to market new products, internationally. All this resulted in unnecessary expenses and long delays in introducing new drugs.

So a necessity to harmonise or make uniform, the testing procedures and regulatory requirements of different countries was felt and the result is the birth of ICH in April 1990.


The birth of ICH took place at a meeting in April 1990, hosted by the EFPIA in Brussels. Representatives of the regulatory agencies and industry associations of Europe, Japan and the USA met primarily to plan an International Conference but the meeting also discussed the wider implications and terms of reference of ICH. The ICH steering committee which was established at that meeting has since met at least twice a year, with the location rotating between the three regions.

The topics first chosen for harmonization were “safety, quality and efficacy and Expert Working Groups were set up to discuss scientific and technical aspects of each harmonization topic.

Steps in ICH Process

The ICH process envisages harmonisatin in 5 steps.

Step-1: Concept paper, guideline development through EWG scientific consensus.

Step-2: EWG and steering committee guideline .

Step-3: Public comments requested and reviewed, drafts revised by regulators.

Step-4: Regulatory parties EWG and steering committee of ¢¢finalized ICH guidelines.

Step-5: Implementation in three regions.

Climatic Zones and Conditions

WHO has issued guidelines, where it is stated that the world is divided into four zones based on the prevailing annual climatic conditions for the purpose of stability testing.

Zone I : temperate

Zone II : subtropical with possible high humidity

Zone III : hot/dry

Zone IV : hot/humid

Tables 1 and 2 gives some interesting data. Table 1 gives the temperatures and relative humidities as recorded in different zones.

Table ¢1: Mean climatic conditions: measured data in the open air and in the storage room 1


Climatic Zone

Measured data in the open air Measured data in storage room
oC %RH oC %RH

 

I

II

III

IV

 

10.9

17.0

24.4

26.5

 

75

70

39

77

 

18.7

21.1

26.0

28.4

 

45

52

54

70


1RH =  relative humidity.

ClimaticZone Calculated data Derived storage conditions(for real-time studies)
oC oC MKT3 %RH oC %RH

 

I

II

III

IV

 

20.0

21.6

26.4

26.7

 

20.0

22.0

27.9

27.4

 

42

52

35

76

 

21

25

30

30

 

45

60

35

70


1Based on: Grimm W. Storage conditions for stability testing in the EC, Japan and USA; the most important market for drug products.  Drug

development and industrial pharmacy, 1993, 19:2705-2830.

2 Calculated temperatures are derived from measured temperatures, but all measured temperatures of less than 19oC were set equal to 19 oC.

3 MKT = mean kinetic temperature

4 RH = relative humidity

Table 2 gives the calculated values of temperature, mean kinetic temperature and relative humidity and also gives derived storage conditions for real time studies. So for example if a manufacturer plans to sell his products in zone-III he/she should do real time studies at 30oc and 35%RH.


What has ICH done so far regarding stability?

It has issued guidelines in six important areas, all of them regarding stability testing of new drugs or dosage forms.

Quality Guidelines Stability=


Q1A (R2) Stability Testing of New Drug Substances and products (Second Revision)

Q1B Stability Testing: Photostability Testing of New Drug Substances and Products.

Q1C Stability Testing for New Dosage Forms

Q1D Bracketing and Matrixing Designs for Stability Testing of Drug Substances and Products.

Q1E Evaluation of Stability Data

Q1F Stability Data Package for Registration Application in Climatic Zones III and IV.


Q 1 A (R2)

I will try to briefly summarize Q1A(R2) for you.

If a manufacturer wants to apply for the registration of a new drug, i.e. if he is applying for a (1) Investigative New Drug Application (IND) or (2) New Drug Application (NDA) or (3) New Drug Application (ANDA) then he has to assure the FDA regarding the drug’s/drug product’s safety, quality and efficacy. For this he has to carry out stability tests and submit stability data. How he should do this is specified by Q1A (R2).

Selection of Batches

Data from formal stability studies should be provided on at least three primary batches of the drug substance. These batches should be made to a minimum of pilot scale by the same synthetic route as that of the production batches.

Specifications which include testing methods and acceptance criteria should be fixed.

Testing frequency:

___________Months________

Long term : 0, 3, 6, 9, 12, 18, 24

Accelerated storage: 0, 3, 6

Storage conditions recommended


General case

Study

Storage condition

Minimum time period covered by data at submission

Long term*

25 oC + 2 oC/60% RH + 5% RH or

30 oC + 2 oC/65% RH + 5% RH

12 months

Intermediate**

30 oC + 2 oC/65% RH + 5% RH

6 months

Accelerated

40 oC + 2 oC/75% RH + 5% RH

6 months

If long-term studies are conducted at 25oC+ 2oC/60% RH + 5% RH and “significant change” occurs at any time during 6 months’ testing at the accelerated storage condition, additional testing at the intermediate storage condition should be conducted and evaluated against significant change criteria.

“Significant change” for a drug substance is defined as failure to meet is specification.

Drug substances intended for storage in a refrigerator

  Study

Storage condition

Minimum time period covered by data at submission

Long term

5 oC + 3 oC

12 months

Accelerated

25 oC + 2 oC/60% RH + 5% RH

6 months


Drug substances intended for storage in a freezer

Study

Storage condition

Minimum time period covered by data at submission

Long term

-20oC + 5 oC

12 months

On the basis of the testing of all these stored products and analysing them for various stability parameters data is obtained and this data is analysed statistically and a storage statement is made on the label.

Almost all conditions are similar for new drug and new drug product.

Significant change for a drug substance is defined as failure to meet its specification.

Significant change for a drug product is defined as

1. A 5% change in assay from its initial value; or failure to meet the acceptance criteria for potency when using biological or immunological procedures;

2. Any degradation product’s exceeding its acceptance criterion;

3. Failure to meet the acceptance criteria for appearance, physical attributes, and functionality test (e.g.: color, phase separation, resuspendibility, caking, hardness, dose delivery per actuation); however, some changes in physical attributes (e.g.: softening of suppositories, melting of creams) may be expected under accelerated conditions; and, as appropriate for the dosage form:

4. Failure to meet the acceptance criterion for pH; or

5. Failure to meet the acceptance criteria for dissolution for 12 dosage units


Stability Testing for Established Drug Substances

WHO has issued guidelines for stability testing of pharmaceutical products containing well established drug substances in conventional dosage forms. The stability of finished pharmaceutical products depends on environmental factors and on product related factors. So stability considerations should be given, the highest priority in the design and formulation of a product. The shelf life should be established with due regard to the climatic zones. To ensure both patient safety and the rational management of drug supplies, it is important that the expiry date and storage conditions are properly indicated on the label.

Let us look at a few definitions here.

Accelerated stability testing

These are the studies designed to increase the rate of chemical degradation and physical change of a drug by using exaggerated storage conditions as part of the formal stability testing programme. The data thus obtained, in addition to those derived from real – time stability studies, may be used to assess longer – term chemical effects under non-accelerated conditions and to evaluate the impact of short-term excursions outside the label storage conditions, as might occur during shipping. The results of accelerated testing studies are not always predictive of physical changes. These are also known as stress testing studies.

Expiry date

The date given on the individual container of a drug product up to and including which the product is expected to remain within specifications if stored correctly. It is established for each batch by adding the shelf-life period to the date of manufacture.

Mean Kinetic Temperature

The single test temperature for a drug product corresponding to the effects on chemical reaction kinetics of a given temperature – time distribution. A mean kinetic temperature is calculated for each of the four world climatic zones according to the formula developed by a scientist known as Hayanes. It is normally higher than the arithmetic mean temperature.

Real time (Long term) stability studies

Experiments on the physical, chemical, biological, biopharmaceutical and microbiological characteristics of a drug, during and beyond the expected shelf life and storage periods of samples under the storage conditions expected in the intended market. The results are used to establish the shelf life, to confirm the projected shelf life and to recommend storage conditions.

Stability tests

A series of tests designed to obtain information on the stability of a pharmaceutical product in order to define its shelf-life and utilization period under specified packging and storage conditions.

The following table gives the main objectives and uses the different types of stability testing


Main Objectives of Stability Testing

Objective

Type of study

Use

To select adequate (from the viewpoint of stability) formulations and container-closure systems

Accelerated

Development of the product

To determine shelf-life and storage conditions

Accelerated and real-time

Development of the product and of the registration dossier

To substantiate the claimed shelf-life

Real-time

Registration dossier

To verify that no changes have been introduced in the formulation or manufacturing process that can adversely affect the stability of the product

Accelerated and real- time

Quality assurance in general, including quality control.


Test Samples

For established products the following schedule is suggested by WHO:

- one batch every other year for formulations considered to be stable, otherwise one batch per year.

- One batch every 3 – 5 years for formulations for which the stability profile has been established, unless a major change has been made, eg: in the formulation or the method of manufacture.


Test Conditions


Example of conditions for accelerated stability testing of products containing relatively stable active ingredients

Storage temperature (oC)   Relative humidity (%) Duration of studies (months)
40 +  2 Zone IV – For hot climatic zones or global market   
  75 +  5 6
40 +  2 Zone II – For temperate and subtropical climatic zones: 3
  75 +  5    


Alternative storage conditions may be observed, in particular, storage for 6 months at a temperature of at least 15oC above the expected actual storage temperature (together with the appropriate relative humidity conditions). Storage at higher temperatures may also be recommended, e.g.3 months at 45 – 50oC and 75% relative humidity (RH) for zone IV

Shelf – Life and Recommended Storage Conditions

The results of stability studies are evaluated with the objective of establishing a tentative shelf life Statistical methods are often used for the interpretation of these results. A tentative shelf – life of 24 months may be established provided the active ingredient is known to be stable.

Products containing less stable active ingredients and formulations not suitable for experimental studies at elevated temperature (eg: suppositories) will need more extensive real time stability studies. The proposed shelf-life should then not exceed twice the period covered by the real time studies.

After the stability of the product has been evaluated, one of the following recommendations as to storage conditions can be prominently indicated on the label.

- store under normal storage contisions1;

- store between 2 and 8oC (under refrigeration, no freezing);

- store below 8 oC (under refrigeration);

- store between -5 and -20oC(in a freezer);

- store below -18oC(in a deep freezer).

Normal storage conditions have been defined by WHO (3) as: â€ÂÂÂÃÂÃÃ