Effect of Humidity Level on Tablet Stability

The level of humidity greatly affects the stability of tablets. Tablets and capsules are protected for moisture by their packing. Degradation of tablets and capsules starts when they get a high moisture content and this also appears in their physical appearance too. There are different ways through which tablet stability is affected as discussed in this article.

1. Deterioration in Hardness

Investigation of various humidity conditions that have an influence on changes in the hardness of a tablet stored for over six months has been conducted. All samples used showed deterioration in hardness at 75% relative humidity and 5-10% at 25 degrees and 10-39% at 45 degrees. There is little difference in deterioration in hardness at 100% relative humidity. At high humidity, tablets absorb moisture which adversely affects its hardness.

2. Effect on Stability

Physical stability of a drug is one thing that should be taken into consideration since it may affect the effectiveness of a drug. Physical stability like certain viscosity has to be maintained for a drug to be effective. When moisture is absorbed into the tablets, it affects physical stability making the tablet to be ineffective. This product here now may be considered as a degradation product. Many people think that these degradation products are inert and are not harmful which is not true. As a matter of fact, cancer is one of the adverse effects caused by these products.

3. Effect on Tablets Properties

One of the most convenient and simplest ways of administering drugs into the body is by use of tablets. physic-chemical properties of tablets such as dissolution rate are highly influenced due to the amount of moisture available in the formulation and the formulation contents of the drug. The widely used technique has been the use of wet granulation for tablet manufacturing. Due to the advantage direct compression has over wet granulation, it makes it be used to a large extent.

4. Effect on Granularity

To successfully investigate the effect of relative humidity on the granularity of tablets, two tablets were used. One of the tablets was stored under desiccating conditions, while the other tablet was stored at high humidity conditions. Then X-ray micro CT images of both tablets were taken differently. X-ray micro CT images were obtained of intact tablets that had been exposed to different humidity levels. A few cracks through the interior were seen at the tablets stored under desiccating conditions. The tablet that was stored under high humidity conditions appears to have more extensive interconnected cracks. A subtle difference in the appearance granularity of the interior can also be seen.
Related: ICH Guidelines for Stability Testing

5. Degradation

The main quality goal of drug tablets is achieving stability. Experiments regarding the degradation of thermal stress are the key tool for the development of the product to arrive at this stated goal for drug substance in solution and liquid product.

Therefore the role of relative humidity and also its interaction with thermal stress should be understood to make it easier to easily guess the kinetics of degradation of solid drugs such as tablets. The humidity conditions that can lead to an unexpected change in the physical state of a tablet, such as hydration/dehydration or melting, and hence the combined storage relative humidity with temperature. The prediction of degradation kinetics can be done successfully. This is achieved for any humidity value.