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Critical surface tensions of pharmaceutical solids
Journal of Pharmaceutical Sciences
|April 1, 1979
Summary
This study determined the critical surface tension of drugs using contact angle measurements. Results showed a narrow range for six drugs and non-linear behavior in mixtures, crucial for pharmaceutical formulation.
Area of Science:
- Physical Chemistry
- Materials Science
- Pharmaceutical Sciences
Background:
- Surface properties of pharmaceutical solids influence drug dissolution and formulation.
- Understanding critical surface tension is vital for predicting drug-tablet interactions and performance.
Purpose of the Study:
- To determine the critical surface tension (CST) of various drugs.
- To investigate the relationship between CST and drug formulation, including mixtures.
Main Methods:
- Sessile drop method to measure advancing contact angles on drug compacts.
- Penetration studies through drug granules to assess surface properties.
- Consistent timing protocols were employed for accurate contact angle determination.
Main Results:
- Critical surface tension for six drugs (analgesics and sulfonamides) ranged from 31 to 33 dynes/cm.
- Penetration studies and compact work yielded consistent CST values for smooth, reflective surfaces.
- Mixtures of phenacetin and microcrystalline cellulose exhibited non-linear CST behavior, with phenacetin dominating at ≥25% concentration.
Conclusions:
- The critical surface tension of common analgesics and sulfonamides falls within a specific range.
- Drug surface properties, particularly in mixtures, deviate from simple additive models.
- Accurate determination of CST is essential for optimizing drug formulation and predicting performance.