How does Granule Size Influence the Stability and Bioavailability of Tablets
1. Influence on Stability
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Moisture Sensitivity: Smaller granules have a larger surface area, which can increase moisture absorption, leading to hydrolytic degradation of moisture-sensitive drugs.
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Oxidation: Increased surface area also accelerates oxidative degradation. Larger granules are relatively more stable in such cases.
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Flow Properties: Properly sized granules improve powder flow during compression, reducing variability and segregation. Poor granule size distribution can lead to inconsistent tablet weight and drug content.
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Physical Stability: Finer particles may cause capping, lamination, or hardness variation due to poor compressibility, affecting long-term stability.
2. Influence on Bioavailability
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Dissolution Rate: Smaller granules dissolve faster because of higher surface area, which enhances drug dissolution rate and bioavailability—important for poorly soluble drugs (BCS Class II & IV).
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Uniformity of Dosage: Optimal granule size ensures uniform distribution of active pharmaceutical ingredient (API), preventing dose variation and ensuring consistent therapeutic effect.
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Disintegration: Appropriate granule size promotes better tablet disintegration, aiding rapid drug release and absorption. Too large granules may delay disintegration and reduce absorption rate.
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Controlled Release: In sustained-release formulations, controlling granule size helps regulate release kinetics, ensuring predictable plasma drug levels.
✅ Summary:
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Smaller granules → Faster dissolution, higher bioavailability, but more prone to instability.
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Larger granules → Better stability, slower dissolution, may lower bioavailability.
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Optimal granule size distribution is essential to balance stability and bioavailability in tablet formulations.
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