Quality control tests for softgel capsules: a summary
Soft capsules are a unique dosage form that presents fascinating challenges for quality control professionals. The distinct composition and manufacturing processes of soft capsules require a thorough understanding of the critical quality attributes and the appropriate testing methods to ensure their safety, efficacy, and stability.
From uniformity of dosage units to disintegration and dissolution testing, this article summarises the key testing parameters for soft capsules.
If you’d like to learn more about the corresponding Ph.Eur. and USP monographs and the specifics of each test, download our comprehensive e-book, “Quality Control Tests of Soft Capsules,” by clicking below!
Uniformity of Dosage Units
One of the key tests for soft capsules is the uniformity of dosage units, which can be assessed through mass variation (MV) for solution fills or content uniformity (CU) for suspension fills. The acceptance value (AV) is calculated based on the deviation of the mean values from the label claim, with an AV of less than or equal to 15% (L1 limit) being the acceptance criterion.
If the L1 limit is exceeded, an additional 20 units are tested, and a second acceptance criterion is applied to the individual values. The European Pharmacopoeia (Ph. Eur.) and United States Pharmacopeia (USP) have harmonized the test and acceptance criteria for uniformity of dosage units.
2. Disintegration
Disintegration testing is another crucial aspect of soft capsule quality control. The disintegration test ensures that the capsule shell ruptures and releases the fill content within the specified time frame. Ph. Eur. and USP have similar requirements for the disintegration test of immediate-release dosage forms, with all units needing to disintegrate within 30 minutes.
Disintegration testing of soft capsules exhibiting crosslinking
3. Dissolution
Dissolution testing is often considered a science in itself when it comes to soft capsules. The main monographs on dissolution testing, EP 2.9.3 and USP <711>, are harmonized and describe the apparatuses and general requirements for immediate-release, prolonged-release, and delayed-release dosage forms.
The selection of dissolution conditions, including the apparatus, should be guided by the limiting phase of dissolution for each product, such as the rupture of the shell, dispersion of the fill, or dissolution of the active ingredient. USP <1094> provides valuable information on dissolution method development specifically for hard and soft capsules, explaining the three main phases of dissolution and offering guidance on the selection of dissolution conditions.
4. Additional Tests
In addition to these critical tests, the assay, identity, and degradation products must be determined, and the microbiological quality should meet the acceptance criteria for non-aqueous oral-use preparations. Depending on the specific characteristics of the drug substance and the formulation concept, additional tests may be necessary.
These tests should be defined based on the identification of the critical quality attributes of the drug product, following a Quality by Design (QbD) approach as outlined in ICH Q8.
Want to learn more about the comprehensive testing strategy for soft capsules and gain expert insights on method development, validation, and troubleshooting? Download our in-depth e-book, "Quality Control Tests of Soft Capsules," for free by clicking below!
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