Abstract
Purpose :
There are mixed reports on the short-term effects of topical phenylephrine on both choroidal thickness and retinal vasculature. We investigated the effect of orally administered α-agonists commonly found in over-the-counter “cold and flu” medications (phenylephrine and pseudoephedrine) on intraocular vasculature.
Methods :
In Experiment 1, healthy participants (n=37) ≥18-years-old with no ocular pathology underwent baseline optical coherence tomography (OCT) measurements with a Zeiss Cirrus 5000 (macular angiography 3x3mm, HD single line 100x scan, and ONH angiography 4.5x4.5mm). An oral dose of 10mg phenylephrine hydrochloride was then administered and OCT measures made every 15 minutes for two hours.
In Experiment 2, healthy participants (n=25) ≥18-years-old with no ocular pathology were randomly administered an oral dose of either 10mg phenylephrine hydrochloride or 60mg pseudoephedrine hydrochloride. Intraocular pressure, blood pressure, and OCT measures were made before and 60 minutes after drug administration. The procedures were repeated with the other drug on a different day.
Results :
In Experiment 1 there was no significant effect of phenylephrine on subfoveal choroidal thickness (SFChT) over two hours (p=0.25), with a maximum, non-significant thinning observed 45 minutes after tablet ingestion (-4.35±14.38μm). Likewise, no significant changes were observed in any angiography measures (macular vessel or perfusion density; foveal avascular zone area, perimeter, or circularity; optic nerve head flux or perfusion density) over two hours (all p>0.05).
In Experiment 2, SFChT showed significant thinning one hour after pseudoephedrine (-1.58±4.11μm; p=0.022) but not phenylephrine (-0.59±4.81μm; p=0.34) ingestion. No significant changes were observed in angiography measures or ocular perfusion pressure one hour after either phenylephrine or pseudoephedrine ingestion (all p>0.05).
Conclusions :
Unlike topical phenylephrine, oral phenylephrine does not significantly alter SFChT. Oral pseudoephedrine, with greater bioavailability, significantly reduces SFChT after one hour. Retinal vascular autoregulation does not appear to be affected by oral α-agonist consumption in healthy eyes. The safety of oral α-agonist use, especially pseudoephedrine, should be investigated in patients with compromised choroidal vasculature.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.