Gabapentin is a pharmaceutical agent that is being used more and more commonly in feline medicine. Some of its applications include pre-veterinary administration for analgesia and sedation, post-operative analgesia, seizure disorders and analgesia for a wide variety of painful conditions. One of these conditions, degenerative joint disease or osteoarthritis (OA), is an extremely common, but under-recognized and under-treated condition in cats.
The authors sought to evaluate the use of gabapentin in osteoarthritic cats by measuring its effect on patient activity levels, as well as owner perceived mobility impairment and quality of life.
The study was designed as a blinded, placebo-controlled, randomized, crossover study. Twenty osteoarthritic cats over the age of ten were evaluated by clients for three mobility impaired activities specific to their cat (Client specific outcome measure CSOM). These evaluations were made weekly throughout the study. Deterioration in impaired activities was defined as a decrease in CSOM of >2. Clients also evaluated a quality of life rating for their pet cat at the end of the study.
Cohorts receiving gabapentin were administered 10 mg/kg PO q12h for 2 weeks, while the second cohort received placebo. Following the 2-week period, treatment protocols were switched between the two groups. No washout phase was included.
Results
While receiving gabapentin, patients had reduced activity level, but significantly greater odds of improved CSOM and QOL scores. Compared to the cohorts receiving placebo first, in the cohorts receiving gabapentin followed by placebo, there was a greater proportion of deterioration in impairment activities. The proportion of cats with worsened QOL did not differ between cohorts. Adverse effects during gabapentin administration included sedation, ataxia, weakness and muscle tremors). One patient receiving placebo treatment experienced lethargy.
The authors conclude that gabapentin may be useful for some signs of pain in cats with osteoarthritis. Given the potential for central sensitization and/or neuropathic pain in chronic osteoarthritis pain, use of drugs which target the central nervous system may be beneficial.
Study limitations
Study limitations to consider include the use of only one dose of gabapentin. Published dosage ranges vary widely (6.5 to 50 mg/kg POq12h). Anecdotal evidence suggests that dosing effects may be very patient-dependent. Side effects may be observed in some patients at low doses while in others, analgesic effects are only accomplished at higher doses. No washout period was included between treatment periods. The authors rightfully point out that since the half-life of gabapentin in cats has been reported to be very short (2.5 to 3 hours), the lack of washout period is not likely a major concern.
The side effect of sedation was thought to impact not only the reports of adverse effects but also the diminished activity level of the patient while on gabapentin as well as assessment by owners or reduced quality of life. Anecdotal evidence does suggest that the side effect of sedation from gabapentin use does reduce or eliminate completely after 2-4 weeks. An extended duration of treatment periods may have altered results for all three of these observations.
Further studies will be needed to provide additional data and support for the use of gabapentin in osteoarthritic cats. At this time, this study provides an excellent baseline for practitioners when considering gabapentin for their osteoarthritic feline patients.
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