초록
Gabapentin is an antiepileptic drug that is structurally similar to ${\gamma}-aminobutyric$ acid (GABA), but does not interact with the GABA receptor. It does not bind significantly to plasma proteins, and is excreted to unchanged form in the urine. The purpose of the present study was to evaluate the bioequivalence of two gabapentin capsules, $Neurontin^{TM}$ capsule 300 mg (Pfizer Pharm. Co., Ltd.) and Kuhnil $Gabapentin^{TM}$ capsule 300 mg (Kuhnil Pharm. Co., Ltd), according to the guidelines of the Korea Food and Drug Administration (KFDA). The release of gabapentin from the two gabapentin formulations in vitro was tested using KP VIII Apparatus II method with various dissolution media (pH 1.2, 4.0, 6.8 buffer solution and water). Twenty six healthy male subjects, $22.46{\pm}1.86$ years in age and $67.64{\pm}7.24$ kg in body weight, were divided into two groups and a randomized $2{\times}2$ cross-over study was employed. After a single capsule containing 300 mg as gabapentin was orally administered, blood samples were taken at predetermined time intervals and the concentrations of gabapentin in serum were determined using HPLC with fluorescence detector. The dissolution profiles of two formulations were similar at all dissolution media. In addition, the pharmacokinetic parameters such as $AUC_t$, $C_{max}$ and $T_{max}$ were calculated and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_t$, $C_{max}$ and untransformed $T_{max}$. The results showed that the differences between two formulations based on the reference drug, $Neurontin^{TM}$ capsule 300 mg, were -2.03, -0.43 and 4.29% for $AUC_t$, $C_{max}$ and $T_{max}$, respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25 $(e.g.,\;log\;0.89{\sim}log\;1.09\;and\;log\;0.91{\sim}log\;1.09$ for $AUC_t$ and $C_{max}$, respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating Kuhnil $Gabapentin^{TM}$ capsule 300 mg was bioequivalent to $Neurontin^{TM}$ capsule 300 mg.
