Objective - To determine the thermal antinociceptive effect of various single doses of gabapentin administered orally in cats. Animals - 6 healthy adult domestic shorthair cats. Procedures - Baseline skin temperature and baseline thermal threshold were determined via application of a thermal probe to the thorax of each cat prior to oral administration (in random order) of an empty capsule (placebo) or a capsule containing 5, 10, or 30 mg of gabapentin/kg (4 experiments/cat). After each treatment, thermal threshold was determined at intervals during an 8-hour period. Plasma gabapentin concentration was measured prior to and at 1-hour intervals after drug administration. Dose and time effects were analyzed by use of a repeated-measures ANOVA. Results - Peak plasma gabapentin concentration increased with increasing gabapentin dose. After administration of the 5, 10, and 30 mg/kg doses, median interval until the greatest gabapentin concentration was detected was 60, 120, and 90 minutes, respectively (interval ranges were 60 to 120 minutes, 60 to 120 minutes, and 60 to 180 minutes, respectively). In the experiments involving administration of the placebo or increasing doses of gabapentin, mean ± SD baseline skin temperature and thermal threshold were 36.8 ± 1.21° C and 45.8 ± 4.4° C, 36.9 ± 1.1° C and 43.1 ± 2.4° C, 37.0 ± 0.7° C and 44.0 ± 1.5° C, and 36.1 ± 1.7° C and 43.3 ± 3.3° C, respectively. There was no significant effect of treatment on thermal threshold. Conclusions and Clinical Relevance - At the doses evaluated, orally administered gabapentin did not affect the thermal threshold in healthy cats and therefore did not appear to provide thermal antinociception.
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