Dissolution, Disintegration, and Shelf Life Testing of Natural Health Products

Changdong Jin, Ph.D., Food/NHP Division, Enviro-Test Laboratories

The normal route for the administration of the majority of natural health products (NHP) is through solid dosage forms, mostly capsules and tablets. Dissolution, disintegration, and shelf life tests are an integral part of the quality testing for NHP. These tests are performed by the manufacturer and also by independent labs on behalf of the manufacturer.

Dissolution Test
A dissolution test provides the dissolution rate of the active ingredients in a solid dosage form. It tests whether the dosage form is formulated and manufactured appropriately in order to ensure that the bioactive ingredients, or the marker compounds, will dissolve in the gastrointestinal tract and be available for absorption. The parameters derived from dissolution test are used to characterize the bioactive ingredient release property, and this property is directly related to the bioavailability. The dissolution property is a very essential quality indicator of time controlled release dosage forms.

Official methods are required for this test. The media solution for the test (often a buffer solution which mimics the gastrointestinal fluid) is controlled at about body temperature, 37¢ªC. The test material (tablet) is inserted into a basket which is submerged in the media. At a prescribed interval, a measured amount of the solution is taken for analysis.

Factors that may influence a dissolution test result include the type of apparatus used, composition and temperature of the medium, rotating speed of the basket or the paddle, time and method of sampling as well as the method used for analysis.

The dissolution property for a solid dosage form is expressed as a percentage of the ingredient released over the time.

Disintegration Test
The disintegration test is often considered as an interim standard for solid dosage forms where there is no dissolution test enforced. It determines whether tablets or capsules disintegrate within a prescribed time when placed in a liquid medium under controlled temperature and stirring motion. The test requires the use of an officially calibrated apparatus. Generally, an NHP dosage form will disintegrate within 20 minutes under this standard disintegration procedure.

Shelf Life Test
The expected shelf life of a product depends on both the potential environmental conditions that the product will be exposed to and how much of the initial quality can be lost before the product should no longer be sold to the consumer. The shelf life is found on the product label as Best Before Date, Expire Date, or Durable Life Date, after which it should no longer be sold to the consumer.

Since the true shelf life of a NHP is usually unknown, it is typically estimated based on assay results of the product from a stability study conducted during the process of the product development. In the analytical laboratory, an accelerated shelf life test is often used. This allows scientists to predict a shelf life over a shorter period of experimental time, often in a few weeks to several months.

A component assay result within +/-5% may still meet the product specifications where the acceptable component content range is 90% to 115%. In contrast to this, shelf life testing requires much higher precision. For example, if a 10% loss of an active component is set as the end point for a product, a test precision error of +/-5% is unacceptable. Thus, a proper experimental design with higher precision is necessary to obtain the kinetic data. Scientists have demonstrated that data collected over a minimum of 8 time points (with certain percentage loss of a component) will give a good confidence level for prediction of shelf life.

The actual experimental determination of shelf life involves sample temperature control (as well as moisture, light, and airflow control, if required), sampling procedure, assay, and assay results processing (modeling). A potency versus time chart, which is derived from a scatter plot with an estimated regression line, confidence interval bands, and prediction interval bands, is then presented in the shelf life prediction.

Other characteristics to be considered in product shelf life prediction may also include color, texture, and microbial content.

A laboratory performing shelf life tests should be accredited in GMP, or GLP, in order to provide the quality required for the predictions.

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