Palmitoylethanolamide intake and systemic endothelial function in ocular hypertensive patients

Palmitoylethanolamide intake and systemic endothelial function in ocular hypertensive patients: results from a single centre, randomized double blind, placebo controlled cross-over study.

Glaucoma is a multi-factorial optic neuropathy of unknown aetiology in which the increased intraocular pressure is the most important risk factor, but also ischaemia, vascular dysregulation, vasospasm and endothelial dysfunction, may prevent the physiological regulation of ocular blood flow, determining modifications in the optic nerve head supply, contributing to the damage of the ganglion cells.

Therapeutically, therefore, both reducing intra ocular pressure (IOP) and improving ocular blood flow may be considered as treatment options both in glaucoma and ocular hypertension. It’s feasible that ameliorating endothelial function may contribute to improve optic nerve head blood supply and to reducing susceptibility of Orthotopic heart transplantation (OHT) patients to develop glaucoma or of glaucoma patients to progress more rapidly.

Palmitoylethanolamide belongs to the endocannabinoid system and it is implicated in the physiology of different human systems, included ocular tissues and vascular system where seems to exert, among others, an important role in the endothelial protection in the rat so it could play a main role in the treatment of glaucoma or OHT patients.

Inclusion criteria:

1. 40 patients aged < 65 years (mean 56.8±8.1)
2. Baseline IOP >= 22 mm/Hg, on at least two measurements (mean 23.11±0.93)
3. Open anterior chamber angle at gonioscopy, cup/disc ratio < 0.4
4. Normal visual field (VF) (MD ❤ dB and PSD < 2.5 dB) and corneal central thickness within normal values
5. 40 healthy control subjects aged matched (mean 56.2±10.4)


Treatment arms: 20 OHT patients randomly assigned to assume a 300 mg oral tablet of palmitoylethanolamide (PEA) two time a day for three months and after two months of wash out switched to treatment with placebo. The others 20 OHT patients randomly assigned to assume placebo and after two months of wash out switched to treatment with palmitoylethanolamide (PEA).

All patients underwent:
1. Ophthalmologic examination including visual acuity and applanation IOP assessment
2. Corneal thickness evaluation with a Tomey SP3000 pachymeter (Tomey Corp., Nagoya, Japan)
4. Biomicroscopy of the anterior and posterior segment with automatic measurement of the C/D area ratio of the optic nerve head with Stratus OCT3 (Zeiss-Humphrey, Dublin, CA).
5. Standard achromatic perimetry (SAP) with a Humphrey Field Analyzer-SITA program (Zeiss-Humphrey, San Leandro, CA)
6. Blood sampling to assess lipid profile and fasting serum glucose.
7. Body mass index calculation
8. Systolic and diastolic blood pressure measurement
9. Assessment of the flow-mediated vasodilatation (FMD) with a Philips ENVISOR echographic machine (Philips Medical Systems, Best, The Netherlands); FMD was calculated as the percentage change in brachial artery diameter in response to reactive hyperemia:
FMD = [(VDHyperemia – VDBaseline)/ VDBaseline] x 100%
VD= Vessel Diameter

Outcome variables:

1. FMD values in OHT patients compared with controls at baseline
2. FMD values in OHT patients randomly assigned to assume Palmitoylethanolamide or placebo for 3 months
3. FMD values in OHT patients after 2 month washout period
4. FMD values in OHT patients after they switched to the other treatment for further 3 months


Three-month PEA intake reduced IOP and led to significantly improved FMD values in OH patients compared to placebo, by ameliorating peripheral endothelial function, and its positive effect lasted longer than the period of PEA consumption. No adverse events were recorded.

Source: Strobbe E, Cellini M, Campos EC. Effectiveness of palmitoylethanolamide on endothelial dysfunction in ocular hypertensive patients: a randomized, placebo-controlled cross-over study. Invest Ophthalmol Vis Sci. 2013 Feb 1;54(2):968-73. doi: 10.1167/iovs.12-10899.

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