Contraindication to the use of ocular phenylephrine in idiopathic orthostatic hypotension.

We studied the effect of topical ocular application of 2.5% phenylephrine ophthalmic solution in patients with idiopathic orthostatic hypotension and in normal subjects. The normal subjects had no pressor effect to the drug. However, the patients with idiopathic orthostatic hypotension, had a marked pressor response. The maximal pressor response in the four patients averaged 44/27 mm Hg. The usual 10% phenylephrine used in practice could have delivered a fourfold greater amount of drug, and presumably would have led to dangerously high blood pressure responses.