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Ionization states in the microenvironment of solid dosage forms: effect of formulation variables and processing.
Ramprakash Govindarajan1, Andrey Zinchuk, Bruno Hancock
1Department of Pharmaceutics, University of Minnesota, 308 Harvard St. SE, Minneapolis, MN 55455, USA. govin002@umn.edu
Pharmaceutical Research
|August 26, 2006
Summary
The microenvironment within solid dosage forms is influenced by excipient properties and processing. Understanding these factors is crucial for predicting drug behavior in pharmaceutical formulations.
Area of Science:
- Pharmaceutical Sciences
- Solid-State Chemistry
- Formulation Development
Background:
- The microenvironment of solid dosage forms significantly impacts drug stability and performance.
- Understanding the physicochemical microenvironment is essential for rational drug formulation design.
Purpose of the Study:
- To evaluate how formulation composition and processing affect the microenvironment in solid dosage forms.
- To utilize indicator probes to measure the microenvironmental conditions within pharmaceutical solids.
Main Methods:
- Sulfonephthalein indicators were incorporated into excipient blends using solvent deposition.
- Diffuse reflectance visible spectroscopy measured indicator ionization to determine an acidity function, pH(eq).
- Indicator ionization was monitored during simulated wet and dry mixing processes.
Main Results:
- The calculated pH(eq) reflected the physicochemical environment experienced by the probe.
- Excipient surface properties and available surface area influenced the blend's microenvironment.
- Probe ionization varied during simulated wet mixing-drying, and excipient suspension pH was not predictive of solid-state ionization.
Conclusions:
- Excipient nature, surface area, processing modifications, and solvent characteristics dictate the microenvironment in solid dosage forms.
- The microenvironment experienced by a drug is a complex interplay of formulation and processing factors.
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