Related Experiment Videos
Hardness anisotropy of acetaminophen crystals
W C Duncan-Hewitt1, D L Mount, A Yu
1Faculty of Pharmacy, University of Toronto, Ontario, Canada.
Pharmaceutical Research
|May 1, 1994
Summary
Acetaminophen hardness is anisotropic, meaning it varies with direction. This study reveals acetaminophen is semiductile, not brittle, due to limited slip systems, impacting tablet manufacturing.
Area of Science:
- Materials Science
- Crystallography
- Pharmaceutical Science
Background:
- Acetaminophen (APAP) exhibits anisotropic mechanical properties, influencing its processing.
- Understanding crystal plasticity is crucial for pharmaceutical tablet formulation and manufacturing.
Purpose of the Study:
- To investigate the anisotropy of acetaminophen hardness.
- To determine the operative slip system(s) governing plastic deformation in acetaminophen crystals.
- To rationalize the observed mechanical behavior and its implications for tabletability.
Main Methods:
- Vickers and Knoop indentation hardness measurements were employed.
- Analysis of Knoop hardness anisotropy based on established models.
- Correlation of indentation results with crystallographic slip systems.
Main Results:
- Acetaminophen hardness is anisotropic.
- Plastic flow is primarily governed by the (010)<001> slip system.
- The limited number of active slip systems (one) leads to apparent brittleness and classifies acetaminophen as semiductile.
Conclusions:
- Acetaminophen's mechanical behavior is dictated by its single operative slip system.
- This anisotropy and semiductile nature can lead to crystal realignment during compaction, potentially causing capping during tablet ejection.
- Precise classification as semiductile is essential for optimizing pharmaceutical processing of acetaminophen.