Stability of Donepezil in an Extemporaneously Prepared Oral Liquid

The stability of donepezil in an extemporaneously prepared oral liquid was studied. An aqueous liquid formulation of donepezil was prepared by reconstituting the powder from triturated 5-mg tablets with equal amounts of deionized water and 70% sorbitol solution with an expected donepezil concentration of 1 mg/mL. Polyethylene terephthalate plastic bottles containing donepezil liquid preparation were stored at ambient room temperature (22°C-26°C) and in the refrigerator (4° C-8°C). After a storage time of 1, 2, 3, and 4 weeks, donepezil liquid samples were analyzed in triplicate for donepezil concentrations by high-performance liquid chromatography. The concentrations of donepezil were found to be within the acceptable limit (±10% of the initial concentration) in all test samples, which indicated that donepezil liquid preparation was stable at room temperature and in the refrigerator for up to 4 weeks. In addition, our study findings indicated that there was no microbial growth in the extemporaneously prepared donepezil liquid preparation after a storage period of 4 weeks in the refrigerator. In summary, the results of our study revealed that donepezil is stable (no significant loss of donepezil concentration and no microbial growth) in an extemporaneously prepared oral liquid when stored in the refrigerator for up to 4 weeks.