Effects of gabapentin and trazodone on electroretinographic responses in clinically normal dogs.

Objective: To compare electroretinographic (ERG) responses obtained in dogs before and after oral administration of gabapentin, trazodone, and a combination of both medications.

Animals: 12 clinically normal dogs.

Procedures: A short-protocol ERG with 20 minutes of dark adaption was recorded for all dogs to establish baseline ERG responses. Dogs then received gabapentin (approx 30 mg/kg), trazadone (approx 20 mg/kg or approx 5 mg/kg), or a combination of gabapentin (approx 20 mg/kg) and trazodone (approx 5 mg/kg) orally, and the same ERG protocol was repeated 2 hours later. Dogs were given a washout period of at least 1 week between treatments.

Results: a-Wave amplitudes were significantly (P = 0.018) decreased after administration of the combination of gabapentin and trazodone. b-Wave amplitudes were significantly decreased after administration of the 20-mg/kg dose of trazodone (P = 0.006) and after administration of the combination of gabapentin and trazodone (P = 0.002). Heavier dogs that received higher total doses of trazodone had decreases in a-wave amplitude after administration of the 20-mg/kg dose of trazodone and in b-wave amplitude after administration of the 5-mg/kg dose of trazodone.

Clinical Relevance: High doses of trazodone and the combination of gabapentin and trazodone significantly decreased a-wave and b-wave amplitudes in clinically normal dogs. However, the effects on retinal responses had little clinical importance. Therefore, these medications can be used safely in a clinical setting; however, further studies are needed in dogs with retinal disease.