The CV% (Coefficient of Variation percentage) in dissolution testing represents the percentage ratio of the standard deviation to the mean, and it's used to express the degree of variability in dissolution results. It's a measure of the precision or repeatability of the dissolution test.
Here's a breakdown:
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Definition: CV% = (Standard Deviation / Mean) * 100
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Purpose: It helps assess the uniformity of drug release from a batch of dosage units (e.g., tablets or capsules). A lower CV% indicates less variability, meaning the drug release profiles are more consistent across the tested units.
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Application in Dissolution: In dissolution testing, CV% is often used as an acceptance criterion for Stage 1 testing, where a small number of units (e.g., n=6) are initially tested. Limits are usually set on the maximum allowable CV% to ensure batch uniformity. In later stages (Stage 2 and Stage 3) with larger sample sizes, the acceptance criteria shift more towards individual values relative to a Q value, and CV% has less importance.
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Example: Imagine a dissolution test where 6 tablets are tested at a specific time point. The amount of drug dissolved from each tablet is: 85%, 90%, 88%, 92%, 87%, and 89%.
- Calculate the mean: (85 + 90 + 88 + 92 + 87 + 89) / 6 = 88.5%
- Calculate the standard deviation: approximately 2.29%
- Calculate the CV%: (2.29 / 88.5) * 100 = 2.59%
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Regulatory Significance: Regulatory guidelines (like those from the FDA and USP) often specify acceptance criteria for dissolution testing, which can include limits on the CV% for Stage 1 testing. These criteria are crucial for demonstrating batch-to-batch consistency and ensuring product quality. For example, in the USP, for immediate-release dosage forms, the acceptance criteria for Stage 1 (n=6) often states that no individual value is less than Q + 5%, and the CV% is not greater than 20%, where Q is the specified amount of drug dissolved, expressed as a percentage of the label claim.
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Relationship to PVT (Performance Verification Test): As stated in the provided reference, CV% is used in PVT acceptance criteria for geometric mean (GM) and CV%. This test is employed to assess the trueness and precision of the results within the context of ISO 5725-6.
