Gabapentin shelf life
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Gabapentin Shelf Life: Stability Insights and Storage Recommendations
Stability of Gabapentin in Aqueous Solutions
Gabapentin, a γ-aminobutyric acid analogue, is widely used as an antiepileptic. Its stability in aqueous solutions is influenced by several factors including pH, buffer concentration, and temperature. Research indicates that gabapentin degrades at varying rates depending on these conditions. The degradation rate is minimal at a pH of approximately 6.0, and the zwitterionic species of gabapentin shows slower degradation compared to its cationic or anionic forms within a pH range of 4.5 to 7.0. Notably, ionic strength does not affect the degradation rate. Based on Arrhenius plots, gabapentin in an aqueous solution at pH 6.0 can have a shelf life of 2 years or more at room temperature .
Stability of Gabapentin Capsules in Original and Repackaged Containers
The stability of gabapentin 300-mg capsules has been evaluated in both original bulk containers and repackaged unit dose blister strips. Under long-term storage conditions (25°C and 60% RH) for one year, and accelerated conditions (40°C and 75% RH) for three months, the capsules maintained their potency, exceeding 97% and 95% respectively. Although repackaged capsules showed significant weight increases, the potency and overall stability remained unaffected. Both original and repackaged capsules were stable throughout the study period, with acceptable levels of lactam degradation product observed under accelerated conditions .
Manufacturing Design Space and Shelf Life Risk Assessment
A comprehensive risk assessment process using Bayesian parameter estimation has been applied to gabapentin tablet formulations. This process involves developing a design space manufacturing model and a shelf life stability model, which share critical quality attributes. Monte Carlo simulations predict the probability of shelf life failure based on manufacturing controls. The models, validated against long-term stability data, provide a robust framework for ensuring the stability of gabapentin tablets under various production conditions .
Development and Stability of Gabapentin Oral Suspensions
Gabapentin is not commercially available in a liquid form, prompting the development of stable oral suspensions. Two formulations were tested: one using 1% methylcellulose in syrup and another using commercially available suspending agents (Ora Plus/Ora Sweet). Both suspensions, stored at 4°C and 25°C, maintained over 90% of their initial concentrations for 91 days at 4°C and 56 days at 25°C. No changes in pH, odor, or physical appearance were observed, indicating that these suspensions are stable under the specified conditions .
Stability of Extemporaneously Compounded Gabapentin Suspensions
Extemporaneously prepared gabapentin suspensions (100 mg/mL) using Oral Mix or Oral Mix SF vehicles were evaluated for stability. Stored at 25°C and 60% RH in amber plastic bottles and syringes, these suspensions remained stable for 90 days. However, crystallization was observed at 5°C, making storage at this temperature inadvisable. The stability was confirmed through organoleptic inspection, pH measurements, and HPLC-UV assays .
Conclusion
Gabapentin exhibits robust stability under various conditions, with aqueous solutions maintaining a shelf life of up to 2 years at room temperature when pH is controlled. Capsules remain stable in both original and repackaged forms under long-term and accelerated conditions. Oral suspensions can be effectively prepared and stored for extended periods, provided they are kept at appropriate temperatures. These findings ensure that gabapentin can be reliably used in different formulations and storage conditions, maintaining its efficacy and safety.
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