Crospovidone SR Granules are a specialized pharmaceutical granule format based on cross-linked polyvinylpyrrolidone, also known as cross-linked PVP, polyvinylpolypyrrolidone (PVPP), and crospovidone. Crospovidone has CAS Number 9003-39-8 and the polymeric formula (C₆H₉NO)ₙ. The current USP-NF monograph defines crospovidone as a water-insoluble synthetic cross-linked homopolymer of N-vinyl-2-pyrrolidone and specifies 11.0%–12.8% nitrogen calculated on the dried basis. USP also identifies Type A and Type B according to particle size.
Crospovidone SR Granules refer to a granulated pharmaceutical formulation intended for a sustained-release application when the finished product has been specifically designed and characterized for prolonged or controlled release.
It is important to distinguish the underlying crospovidone material from the finished SR granule system. Crospovidone itself is a water-insoluble cross-linked polymer and is primarily used as a pharmaceutical disintegrant. It should not be described as a universal sustained-release polymer.
The sustained-release performance of an SR granule therefore depends on the complete formulation, including the active ingredient, release-controlling materials, coating system, granule structure and manufacturing process.
Cross-linked polyvinylpyrrolidone is commonly known as crospovidone or polyvinylpolypyrrolidone (PVPP). Unlike linear povidone, cross-linking produces an insoluble polymeric structure.
The current USP-NF monograph identifies crospovidone as 1-ethenyl-2-pyrrolidinone homopolymer and 1-vinyl-2-pyrrolidinone homopolymer, with CAS Number 9003-39-8. It specifies nitrogen content of 11.0%–12.8% on the dried basis.
Crospovidone is insoluble in water and common solvents. FCC describes the underlying material as a white to off-white, hygroscopic, free-flowing crosslinked polymer.
Sustained-release granules are designed to modify the rate at which an incorporated active ingredient becomes available from the dosage form. Depending on the formulation, controlled release can be achieved using polymeric matrices, functional coatings, multiparticulate structures or combinations of release-controlling excipients.
For this reason, an SR granule product requires product-specific characterization.
Important characteristics can include:
Numerical values for these parameters should be taken from the approved product specification or certificate of analysis.
Crospovidone is established as a pharmaceutical excipient and is commonly associated with disintegration functionality. Its water-insoluble cross-linked structure allows liquid uptake without dissolving in water in the same manner as soluble polymers.
Accordingly, if a finished SR granule contains crospovidone together with other release-controlling components, the sustained-release performance should be attributed to the complete formulation and release-control system rather than to crospovidone alone.
Published formulation work also demonstrates that crospovidone can occur as one component of controlled-release formulations together with other functional polymers. This reinforces the importance of evaluating the complete formulation rather than assigning sustained-release functionality to crospovidone alone.
A pharmaceutical-grade SR granule product can require control of both the underlying excipient and the finished granule characteristics.
The underlying crospovidone may be evaluated for identity, nitrogen content, moisture-related characteristics, residue on ignition and other applicable pharmacopoeial requirements.
The finished SR granules may additionally require evaluation of:
The actual requirements depend on the finished product specification.
The defining characteristic of an SR granule system is its controlled release profile. Unlike an immediate-release formulation, an appropriately designed sustained-release system is intended to modify the release rate over a specified period.
Dissolution testing is therefore an important product-specific quality attribute for an SR granule system.
However, there is no universal dissolution profile that can correctly be assigned to every product called “Crospovidone SR Granules.” The dissolution method, media, sampling intervals and acceptance criteria should come from the actual product specification and formulation design.
Therefore, generic claims such as “releases for 12 hours” or “releases for 24 hours” should not be used unless supported by the actual product data.
Controlled granule characteristics are important for consistent pharmaceutical processing and performance.
Depending on the product specification, relevant properties may include particle-size distribution, D10, D50, D90, bulk density, tapped density, flow characteristics, moisture and granule strength.
For crospovidone, particle size is also relevant because the current USP-NF monograph recognizes Type A and Type B materials according to particle size.
Finished SR granules may require additional control of coating or matrix characteristics where these are responsible for the release profile.
Crospovidone SR Granules may be evaluated for pharmaceutical applications including:
The exact application depends on the composition and validated performance of the finished product.
The current USP-NF Crospovidone monograph identifies the material as a water-insoluble synthetic cross-linked homopolymer of N-vinyl-2-pyrrolidone. It specifies CAS Number 9003-39-8, polymeric formula (C₆H₉NO)ₙ and nitrogen content of 11.0%–12.8% calculated on the dried basis.
USP also identifies Type A and Type B crospovidone according to particle size.
Where USP/NF, BP or Ph. Eur. compliance is claimed, the actual grade and current applicable specification should support the claim.
Quality control should distinguish between the crospovidone excipient specifications and the finished SR granule specifications.
For the underlying crospovidone, relevant characteristics include identification, nitrogen content and applicable pharmacopoeial quality attributes.
For finished SR granules, additional product-specific testing may include particle-size distribution, moisture, density, coating characteristics, release-controlling polymer characteristics and dissolution performance.
The finished product specification should define the acceptance criteria for these parameters.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.2% |
| Heavy Metals | NMT 10 ppm |
| pH (1% Solution) | 2.0 – 4.0 |
| Individual Impurity | NMT 0.5% |
| Water Content | NMT 0.5% |