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C. M. Clemson, R. Tzekov, M. P. Krebs, J. Checchi, C. Bigelow, S. Kaushal; Therapeutic Potential of Valproic Acid for Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4794.
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Prior work has shown that Valproic Acid (VPA) has multiple biologic properties that make it a potential retinal therapeutic including: neuroprotection, apoptosis inhibition, and microglial activation. In our laboratory VPA was identified as a potent molecular chaperone, increasing the yield of properly folded mutant rhodopsin. The purpose of this study was to examine the efficacy and safety of Valproic Acid (VPA) in patients with Retinitis Pigmentosa (RP).
We performed a retrospective chart review of patients treated off -label with VPA at the University of Florida. Visual fields (VF) at baseline and follow up were defined using digitized Goldmann Kinetic Perimetry tracings from seven patients on short courses of VPA (average 4 months). VF areas for each eye were log transformed and vision loss/gain relative to baseline was calculated. Best corrected visual acuity (transformed to logMAR values) was also evaluated.
The visual fields of 5 of 7 patients increased with treatment. In one case, the improvement in functioning retinal area was confirmed at two time points (23 and 27 weeks). Of the 13 eyes examined, 9 eyes had improved visual field on treatment, two eyes had decreased visual field and two eyes experienced no change with an overall average increase of 11%. Assuming typical loss in VF area without treatment, this increase in VF was statistically significant (p<.02). An average decrease in logMAR scores was seen in these 13 eyes, which was significant (p<.02) assuming no loss in acuity without treatment. Side effects were mild and well tolerated.
Treatment with VPA does not provide significant harm and is suggestive of a therapeutic benefit to patients with RP. These results are encouraging because the dosage used was less than half the conventional dose used for anti-convulsant therapy. A placebo-controlled clinical trial will be necessary to rigorously assess the efficacy and safety of VPA for RP.
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