Managing anxiety in hospitalized dogs is an ongoing challenge in veterinary practice. For veterinary ophthalmologists, managing anxiety in dogs is a particular concern when performing presurgical diagnostic testing, including electroretinography (ERG), for cataract surgery.
Trazodone has been effectively used in dogs to reduce anxiety and facilitate veterinary procedures and postoperative confinement1–3 and is commonly administered orally to reduce stress and anxiety during hospitalization of veterinary patients. Trazodone is classified as a serotonin antagonist and reuptake inhibitor and is well-tolerated in dogs.4 Similarly, gabapentin, an antiepileptic drug that binds to voltage-gated calcium channels, acting presynaptically to decrease the release of excitatory neurotransmitters and that may increase brain concentrations of γ-aminobutyric acid or antagonize α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, is thought to have anxiolytic and analgesic effects in dogs.5–9 Both medications reach clinically relevant plasma concentrations 2 hours after oral administration.4,7
Electroretinography involves recording electrical responses generated by retinal neurons and supporting cells when the eye is stimulated by light.10 In clinical practice, this test is commonly performed in dogs to evaluate for the presence of retinal function prior to cataract surgery and to distinguish retinal amaurosis from postretinal amaurosis.11 In these scenarios, clinicians often use short ERG protocols to assess overall retinal function rather than the longer, more-sophisticated protocols needed to diagnose specific photoreceptor conditions.12–14
Little is known about the effects of trazodone or gabapentin on electrical responses of the retina, although their mechanisms of action indicate these medications may impact retinal cell function. Trazodone may affect serotonin signaling between amacrine neurons and bipolar cells in the retina.15 Gabapentin has been shown to have effects on voltage-gated calcium channels in retinal ganglion cells and, potentially, other cells in the retina of laboratory animals.16
The objective of the study reported here was to compare ERG recordings obtained in clinically normal dogs before and after oral administration of gabapentin, trazodone, or a combination of both medications. Specifically, we wanted to determine whether trazodone or gabapentin would have clinically important effects on ERG responses in dogs.
No third-party funding or support was received in connection with this study or the writing or publication of the manuscript. The authors declare that there were no conflicts of interest.
The authors thank Shelby Moorehead, Amber Helmling, and Andrew Yu for technical assistance.
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