Things to know about stability testing     

Stability testing helps to find the quality of the product by determining its reaction under the influence of external factors such as light, humidity, and temperature.

This process determines whether there is any effect on the integrity and efficiency of the end product due to any physical, chemical, or microbial changes.

Stability studies are commonly used in the pharmaceutical, food and beverages, and cosmetics industries. Only after this test, the product’s shelf life and storage guidelines will be determined.

Types of Stability Testing

There are two common types of stability testing,

  • Real-time testing.
  • Accelerated testing.

In Real-time testing, the product is stored in the recommended condition with required safety procedures and is continuously monitored until it fails. The product would be tested every quarterly for the first year, and twice during the second year, and once each year thereafter. 

In Accelerated testing, the product will be placed in a fabricated environment, and the product is made to react with different factors like light and humidity, which are accelerated. With the help of this study, degradation is determined.

Guidelines for Stability Testing in Pharmaceuticals: 

Formal stability testing includes accelerated and long term testing and is generally done on two primary batches of production for stable drug products. Three batches would be considered for susceptible drug products.

During the submission of a new drug application, the accelerated stability testing data at 40 degrees Celsius for a minimum of six months should also be submitted. If the product is found stable for six months under the accelerated stability testing conditions, then the product will be assigned 24 months of shelf life.

For any product that is to be assigned with a shelf life of more than 24 months, real-time stability testing data should be available.

If the drug formulation completes a long term stability testing for 36 months or more, then it can be assigned with a shelf life of 36 months.

The product will be considered as a new product for stability study if the primary material of the packaging is being changed. 

If a drug product has different doses with the same formulation but differs in the production method, then the drug of each dose will be considered as a new product. Stability testing is done separately for each dose. 

The drug product will be undergoing the test with a frequent interval of time in long term stability testing, such as once in every three months for the first year, and every six months during the second year, and once a year from thereafter until the determining shelf life.

For accelerated testing, the product will be tested on an interval of three and six months.

The stability samples should not be labelled with terms such as room temperature and ambient temperature. It should be labelled with specific details.

The testing should cover the attributes of the drug product that tends to change during the storage period, which will affect the quality and safety of the drug. 

If three batches are chosen for stability testing, then out of those three, two batches should be pilot scale batches. Photostability testing should be performed at least in one primary batch.

What is a pilot-scale batch?

A pilot-scale batch is one produced exactly as the full production batch following the same procedures. The product will also be packed with the same packaging intended to do the final packaging of a finished product. This batch will then be used for stability testing.

We all know that climatic conditions change according to geographical change, and hence different countries have different climates. So the guidelines for stability testing should not be the same for all the countries.

The testing should be carried out by considering the market and climatic condition in the area where the drug product is about to be used.

So in order to determine the expiration date with maximum precision, the world is divided into four zones based on its climatic conditions.

Protocol for Stability testing

The protocol is a written document that conveys the significant procedures of the testing to be performed. The protocol depends on the drug dosage and also the intended packaging. 

The protocol should include the region on which the drug is to be marketed that is proposed by ICH. An effective protocol of the stability study should consist of the following :

Number of Batches

Generally, the selection of the batch for testing should be random from the pilot batches. The data from laboratory scale batches of the development stage is used as additional information and are not considered as primary stability data.

Test storage condition

Stability study on a finished drug product must provide the information about storage, usage, and if appropriate, then dilution of the product. The labelled expiration date depends on the long term stability testing that is conducted.

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