Chemical Stability of Phenytoin Extemporaneous Oral Suspensions

Abstract

Background and Objective: Because the oral liquid dosage form of phenytoin is unavailable in Thailand, phenytoin suspension is extemporaneously prepared in hospitals for patients that need nasogastric tube feeding. To determine an expiry date of the prepared products, the chemical stability of phenytoin extemporaneous oral suspension was studied for a period of 56-days.

Methods: This chemical stability study was an experimental design, conducted at Srinagarind hospital. Phenytoin suspension at concentration of 10 mg/ml was prepared with triturated Dilantin Infatab™50 mg and our formulated vehicle and stored at room temperature. The samples were analyzed for the concentrations of phenytoin on days 0, 7, 14, 28, 42 and 56 using HPLC.

Results: The mean percentages of labeled amount were 98.48, 99.24. 99.48, 98.02, 96.83 and 96.41 on days 0, 7, 14, 28, 42 and 56 respectively.

Conclusions: Throughout the 56-days period of study, the mean percentages of labeled amount were within 95 - 105, in the range of standard content uniformity of USP XXXIV. The results of this study indicated that the phenytoin extemporaneous oral suspension was stable at least for 56 days when stored at room temperature.