Weight Variation Analysis (USP <905>)
Let's Think Step-by-Step: Weight Variation Calculation
Problem: We have 20 tablets with weights ranging from 248-252 mg. Average weight: 250 mg. Are they compliant with USP <905>?
Step 1: Determine the acceptance criteria based on tablet weight
- For tablets ≤130 mg: ±10% deviation allowed
- For tablets 130-324 mg: ±7.5% deviation allowed
- For tablets >324 mg: ±5% deviation allowed
- Our tablets (250 mg) fall in category 2: ±7.5%
Step 2: Calculate percentage deviation for each tablet
- % Deviation = |Individual Weight - Average Weight| / Average Weight × 100
- Example: Tablet 1 = |248 - 250| / 250 × 100 = 0.8%
- Example: Tablet 2 = |252 - 250| / 250 × 100 = 0.8%
- Calculate for all 20 tablets
Step 3: Check compliance criteria
- No individual tablet should exceed ±7.5% deviation
- Count how many tablets (if any) exceed this limit
- If ≤2 tablets exceed limit: PASS
- If >2 tablets exceed limit: FAIL
Pharmaceutical Example: Immediate Release Tablets
Data: 20 tablets of 250 mg strength
Tablet # | Weight (mg) | % Deviation | Compliance |
---|---|---|---|
1 | 248.0 | 0.8% | PASS |
2 | 252.0 | 0.8% | PASS |
3 | 249.5 | 0.2% | PASS |
... | ... | ... | ... |
Result: All tablets within ±7.5% limit → COMPLIANT
💻 Interactive Weight Variation Calculator
Content Uniformity Testing
Let's Think Step-by-Step: Acceptance Value (AV) Calculation
Step 1: Understand the Acceptance Value formula
- AV = |M - x̄| + ks
- M = Reference value (usually 100% or label claim)
- x̄ = Sample mean (%)
- k = Acceptability constant (depends on sample size)
- s = Sample standard deviation
Step 2: Determine k values based on sample size
- For n = 10: k = 2.4
- For n = 30: k = 2.0
- Use appropriate k value for your sample size
Step 3: Calculate AV and interpret results
- Calculate sample mean and standard deviation
- Substitute values into AV formula
- If AV ≤ 15.0: PASS
- If AV > 15.0: Proceed to next stage or FAIL
where M = 100%, k = 2.4 (n=10) or 2.0 (n=30)
Pharmaceutical Example: Content Uniformity L1 Testing
Data: 10 tablets tested for drug content
Results (%): 98.2, 101.5, 99.8, 100.3, 97.9, 102.1, 99.5, 100.8, 98.7, 101.2
Calculation:
- x̄ = (98.2 + 101.5 + ... + 101.2) / 10 = 100.0%
- s = 1.47% (using Excel STDEV function)
- M = 100% (reference value)
- k = 2.4 (for n=10)
- AV = |100 - 100.0| + 2.4 × 1.47 = 0 + 3.53 = 3.53
Interpretation: AV = 3.53 ≤ 15.0 → L1 PASS
💻 Interactive Content Uniformity Calculator
Hardness & Friability Statistics
Let's Think Step-by-Step: Tablet Physical Properties Analysis
Step 1: Calculate hardness statistics
- Mean hardness = Σ(hardness values) / n
- Standard deviation = √[Σ(x - x̄)² / (n-1)]
- CV% = (Standard deviation / Mean) × 100
- Typical acceptance: CV% < 15%
Step 2: Evaluate friability
- % Friability = (Initial weight - Final weight) / Initial weight × 100
- Typical acceptance: Friability < 1.0%
- Document any capping or lamination
Pharmaceutical Example: Physical Properties Assessment
Hardness Data (kp): 6.2, 6.8, 6.5, 6.1, 6.9, 6.4, 6.7, 6.3, 6.6, 6.5
Friability Test: Initial weight: 6.5027 g, Final weight: 6.4892 g
Hardness Calculation:
- Mean = (6.2 + 6.8 + ... + 6.5) / 10 = 6.5 kp
- SD = 0.27 kp
- CV% = (0.27 / 6.5) × 100 = 4.2%
Friability Calculation:
- % Friability = (6.5027 - 6.4892) / 6.5027 × 100
- % Friability = 0.0135 / 6.5027 × 100 = 0.21%
Results: Hardness CV% = 4.2% PASS, Friability = 0.21% PASS