The stability challenges for pharmaceutical products

From physical problems to chemical degradation of active ingredients, the lack of stability can be catastrophic to pharmaceutical products. Here we consider why testing is essential to ensuring medicines are fit for use.


Light, humidity and temperature changes can wreak havoc on pharmaceutical products, with potentially dangerous results. From physical problems such as crumbling tablets to chemical degradation of active ingredients or microbiological attacks, a lack of stability can be catastrophic.

Stability testing is an essential part of drug development to ensure that marketed products remain safe and effective under different conditions. The results are also used to determine a suitable shelf-life for a drug product and to recommend long-term storage. Carefully selected and validated tests really help to smooth the process of taking a drug on the path to market.


Stress testing is likely to be carried out on one batch of a drug substance to look for possible degradation products formed under different conditions by changing the temperature, humidity and oxidation level. "Degradation is not just about controlling potentially toxic breakdown products and reduction in potency of the drug," says Steve Alley, project manager in pharmaceutical development at UK Contract Research Organisation RSSL. "It’s also about the break-down mechanisms that may make the drug more potent."

Early stability studies help identify the ideal formulation from a host of different candidates to take forward for further testing. They also aid analysts in selecting the best methods for further stability tests, which then mimic real-life storage in different global regions. "Early stability is very much about identifying the ideal formulation to take forward so you have a number of different candidates and, through your developed methods," says Alley, "you identify those that offer the most stability on storage but also those that are going to be the most compliant for patient use. It’s absolutely pivotal to ensure the link is made between execution of drug degradation studies – identifying key degradation mechanisms – and using this body of data to determine suitable formulation candidates that can be effectively monitored via a stability study."


Stability tests follow guidelines set out by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH). These guidelines recommend different testing protocols for climactic zones around the globe. For example, storage stability tests can range from temperatures from as low as -80°C to 40°C, with relative humidity up to 75%, following ICH protocols.

An important aspect of the job is to make sure that light exposure does not result in any changes that could potentially affect patient safety. Photostability needs to be tested on an active substance, the final drug formulation and the packaged product. Substances also need to be monitored in a container that is the same as or that simulates the proposed final packaging – again, even subtle changes to a product’s packaging can dramatically affect stability.

Originally published through Chemistry, May 2019.

Read the full article here.

For further information or to discuss your requirements, please contact the RSSL customer services team on +44 (0)118 918 4076 or email