Stability of allopurinol suspension compounded from tablets

Area of Science:

• Pharmaceutical Sciences
• Drug Stability
• Formulation Development

Background:

• Allopurinol is a medication used to treat gout and hyperuricemia.
• Extemporaneous suspensions offer a flexible alternative for patients requiring specific dosages.
• Assessing the stability of compounded formulations is crucial for ensuring therapeutic efficacy and patient safety.

Purpose of the Study:

• To evaluate the stability of allopurinol as an extemporaneous suspension compounded from tablets.
• To determine the shelf-life and degradation kinetics of the allopurinol suspension.
• To assess the physical characteristics, including homogeneity, redispersibility, and pourability, of the compounded suspension.

Main Methods:

• Allopurinol suspension (20 mg/mL) was prepared using pulverized tablets, sodium carboxymethylcellulose, magnesium aluminum silicate, and Lycasin.
• Samples were stored at elevated temperatures (50-80°C) for 97 days.
• Stability was assessed using a stability-indicating high-performance liquid chromatography assay, visual inspection, and evaluation of physical properties.
• Aqueous solubility and degradation kinetics were studied, with shelf-life calculated using the Arrhenius plot.

Main Results:

• The allopurinol suspension remained homogenous with no caking or settling throughout the study.
• The compounded suspension was found to be pharmaceutically acceptable, easily pourable, and redispersible.
• The energy of activation was calculated as 21.92 kcal/mol.
• The predicted shelf-life (t90) at room temperature was determined to be 8.3 years.

Conclusions:

• Extemporaneously compounded allopurinol suspension from tablets is a stable and viable pharmaceutical formulation.
• The formulation exhibits excellent physical stability and a long predicted shelf-life, suitable for clinical use.
• This study supports the use of compounded allopurinol suspensions as a stable alternative for patients.