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T.I. Metelitsina, J.E. Grunwald, M.G. Maguire, J.C. DuPont; Effect of Niacin on the Choroidal Circulation of Patients with Age-related Macular Degeneration (AMD) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):329.
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Purpose: Because previous studies have suggested that choroidal flow may be decreased in AMD, we investigated the choroidal circulatory effects of Niacin, a potent vasodilator. Methods: A double-blind, randomized, crossover study was performed in 12 AMD patients with bilateral drusen and a mean age of 72 ± 7 years (± 1SD). Visual acuity was 20/40 or better in the study eye. All subjects received a single oral dose of Niacin (six subjects received 500mg and six received 250mg), or matching placebo on two separate occasions, at least 3 days apart. Following pupillary dilatation, laser Doppler flowmetry (Oculix) was used to assess relative choroidal blood velocity (ChB Vel), volume (ChB Vol) and flow (ChB Flow) in the center of the fovea of the study eye at baseline, 30 min and 90 min after dosing. Prior to flow measurements, visual acuity (VA) and contrast sensitivity (CS) were determined. Mean arterial blood pressure (BPm), heart rate and intraocular pressure (IOP) were monitored following each set of blood flow measurements and ocular perfusion pressure (PP) was estimated. Results: Mean ChB Vol at baseline, 30 min and 90 min were 0.21 ± 0.05 AU (arbitrary units; mean ± SD), 0.21 ± 0.05AU and 0.21 ± 0.06AU following placebo, and 0.19 ± 0.06AU, 0.23 ± 0.06 AU and 0.19 ± 0.06AU following Niacin. In comparison to placebo, a statistically significant 24% increase in ChB Vol was observed 30 min after Niacin administration (ANOVA, P < 0.05). Further analysis showed that most of the circulatory effect was observed in the Niacin 500 mg group (39% increase, t-test, p=0.04) rather than the 250 mg group (10 % increase, p=0.36). Also at 30 min, ChB Vel in the 500 mg group decreased by 23% (p=0.03). There were no statistically significant changes in any of the choroidal circulatory parameters at 90 minutes or at either time in ChB Flow, PP, VA and CS. We have estimated that we have 96% power to detect 20% changes in ChB Flow. In comparison to placebo, there was a significant decrease in BPm of 9% (t-test, p=0.02) at 30 minutes after Niacin administration and a significant increase in heart rate of 7% (p=0.01) at 30 minutes and decrease of 9% (p=0.05) at 90 minutes. A significant decrease in IOP of 23% (p=0.01) was also seen at 30 minutes after Niacin. Conclusions: In comparison to placebo, a significant increase of 24% in ChB Vol was observed at 30 min after Niacin administration. This most probably was due to dilatation of the choroidal vasculature, an effect that is similar to that seen in other vascular tissues. However, because of a simultaneous decrease in ChB Vel, no significant change in ChB flow was detected.
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