Development of two stable oral suspensions for gabapentin

Abstract

Gabapentin is not available in a liquid dosage form for clinical use. This study was designed to develop two oral gabapentin suspensions and determine their stability under refrigeration or at room temperature. Commercially available gabapentin capsules were used to prepare two suspensions: one in extemporaneously prepared 1% methylcellulose in syrup (1:1) and another in equal volumes of commercially available suspending agents/syrup (Ora Plus/Ora Sweet). Each suspension containing gabapentin (100 mg/mL) was stored in 10 plastic prescription bottles; five were stored at 4°C and five at 25°C. Three 500-μL samples were collected immediately after preparation (day 0) and on days 7, 14, 28, 42, 56, 70, and 91. Gabapentin was measured by accurate, reproducible, specific, and stability-indicating high-performance liquid chromatography (n = 15). The observed mean concentrations exceeded 90% of the initial concentrations in both suspensions for 91 days at 4°C and 56 days at 25°C. No change in pH, odor, or physical appearance was observed. On the basis of these results, stable oral suspensions of gabapentin can be prepared and stored in plastic prescription bottles for 91 days at 4°C or 56 days at 25°C.