Comparison of the stability of split and intact gabapentin tablets

The purpose of this study was to determine the stability differences between split and intact gabapentin tablets. Gabapentin tablets from three different manufacturers (G1, G2 and G3) were tested for a period of 9 weeks under long-term (25 degrees C/60% RH) and intermediate stability (30 degrees C/60% RH) storage conditions after storage in closed amber pharmacy dispensing containers. Samples were analyzed for dissolution and potency using validated HPLC methods. Potency test also included the quantitation of gabapentin's main degradation product. Tablets from all manufacturers and at all time points had potency >90%. At 9 weeks, a statistically significant decrease (p<0.02) in gabapentin potency was observed for the whole and split G2 and G3 tablets under the intermediate storage conditions. At the end of 9 weeks, all samples also showed slightly higher levels of degradation product which was statistically significant (p<0.01) for samples stored under intermediate stability storage conditions and exceeded the proposed USP (PF, 2006) limit for the G3 split and intact tablets. No difference was observed between the potency and dissolution of the intact and the split tablets from the same manufacturer and the three products tested remained stable throughout the study period. The results suggest that splitting of gabapentin tablets did not affect the stability of these particular drug products tested as part of this study when stored under normal storage conditions for a period of up to 9 weeks. However, the results should not be extrapolated to other gabapentin drug products and to other tablet dosage forms.