All of the OH patients who were included at the onset of the study completed the study. At baseline, FMD values of the OH patients were significantly lower than FMD values of the controls (6.06 ± 0.60% vs. 10.85 ± 1.80%,
P < 0.001,
Table 1). No significant differences were evaluated between demographic and clinical parameters of OH subjects randomized to PEA and those randomized to placebo (
Table 3).
At T1, patients who were undergoing PEA therapy (Group A) showed a significant improvement in FMD values (8.46 ± 1.09% vs. 6.08 ± 0.62%,
P < 0.001,
r = 0.96) and a significant IOP reduction 22.18 ± 1.26 vs. 23.03 ± 0.88 mm Hg,
P < 0.001), whereas subjects who were administered a placebo (Group B) had stable FMD and IOP values (6.05 ± 0.68% vs. 6.04 ± 0.58%,
P > 0.05 and 22.95 ± 0.90 vs. 23.25 ± 0.76 mm Hg,
P > 0.05, respectively, see
Figure).
After 2 months of washout, Group A maintained better FMD values than at baseline (6.59 ± 0.33% vs. 6.08 ± 0.62%, P < 0.05) and IOP moved from 22.18 ± 1.26 to 22.88 ± 0.85 mm Hg (P < 0.001), whereas FMD and IOP of Group B did not show any significant change. Then, each patient switched to the other treatment, depending on the first drug received, and at T3, subjects who started PEA intake showed a significant improvement in their FMD and a significant IOP reduction (8.52 ± 1.07% vs. 6.05 ± 0.68%, P < 0.001, r = 0.97 and 22.43 ± 1.17 vs. 23.03 ± 0.83 mm Hg, P < 0.01, respectively), whereas in patients who started the placebo, FMD and IOP moved from 6.59 ± 0.33% to 6.19 ± 0.41% (P < 0.001) and from 22.88 ± 0.85 to 22.78 ± 1 mm Hg (P > 0.05), respectively (see Figure). As regards the relationship between FMD and IOP values, there was a very good correlation in both OH groups at baseline (r = 0.605, P < 0.004 for Group A and r = 0.707, P < 0.001 for Group B) and after PEA intake (r = 0.887, P < 0.0001 for Group A and r = 0.944, P < 0.0001 for Group B). None of the study patients discontinued therapy before the end of the treatment period because they did not experience either systemic/local adverse events or intolerance to PEA.