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Stability studies of gabapentin in aqueous solutions
E Zour1, S A Lodhi, R U Nesbitt
1Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, Morris Plains, New Jersey 07950.
Pharmaceutical Research
|May 1, 1992
Summary
Gabapentin solution stability was studied to create a liquid formulation. Optimal stability, with a shelf life of over 2 years, was achieved at pH 6.0, with minimal degradation.
Area of Science:
- Pharmaceutical Chemistry
- Drug Stability Studies
Background:
- Gabapentin, a gamma-aminobutyric acid analogue, is an established antiepileptic drug.
- Development of a stable liquid formulation for gabapentin is desirable for patient convenience and administration.
Purpose of the Study:
- To investigate the solution stability of gabapentin in various buffered systems.
- To determine optimal conditions for formulating a stable liquid gabapentin product.
Main Methods:
- Gabapentin degradation was monitored across a range of pH values, buffer concentrations, ionic strengths, and temperatures.
- Kinetic analysis and Arrhenius plots were employed to assess degradation rates and predict shelf life.
Main Results:
- Degradation rate increased with buffer concentration and temperature.
- Minimum degradation occurred at approximately pH 6.0.
- Zwitterionic gabapentin exhibited slower solvent-catalyzed degradation than ionic forms between pH 4.5 and 7.0.
- Ionic strength did not impact degradation rate.
Conclusions:
- Gabapentin aqueous solutions at pH 6.0 demonstrate excellent stability, with a predicted shelf life exceeding 2 years at room temperature.
- These findings facilitate the development of stable, liquid gabapentin formulations.