Abstract
The stability of gabapentin pediatric oral suspension prepared from commercially available 400 mg capsules in King Khaled National Guard Hospital, Jeddah, Saudi Arabia was investigated. The extemporaneously compounded 100 mg/mL, oral gabapentin suspension in methylcellulose vehicle was stored in absence of light at 2-8 degrees C in the refrigerator for 3 months. Physical stability (e.g. signs of caking, ease of pouring/redistribution), in addition to pH analysis, zeta potential, conductivity, polarity and mobility were determined and the results revealed appreciable changes throughout the storage period. Chemical stability of gabapentin in suspension was measured using accurate, reproducible, specific, and stability-indicating high-performance liquid chromatography (HPLC) assay. The mean gabapentin concentration was 95.11 mg/mL in freshly prepared suspension compared to 75.86 and 69.86 mg/mL in suspensions stored for two and three months at 2-8 degrees C in the refrigerator, respectively. Additionally, the anticonvulsant activity of gabapentin suspensions stored for one and three months was evaluated using female mice injected with picrotoxin (7 mg/kg, SC). One month stored gabapentin suspension (100mg/kg, i.p) caused a significant decrease in the duration of picrotoxin-induced hind limb tonic extension compared with the control group (P < 0.05), whereas the administration of the three months stored gabapentin suspension to mice produced insignificant effect. Both tested gabapentin suspensions showed 100% protection against picrotoxin-induced mortality. Therefore, we recommend using commercial gabapentin solution for safety and efficacy.