Clonidine. Effects of a topically administered solution on intraocular pressure and blood pressure in open-angle glaucoma
R. Harrison and C. S. Kaufmann
A double-blind crossover study to determine the effects on intraocular
pressure (IOP) and blood pressure of topically instilled 0.125% and 0.25%
solutions of clonidine hydrochloride by comparison with a 2% pilocarpine
hydrochloride solution and placebo was carried out in a total of 21
patients with open-angle glaucoma, each of whom received a single drop of
each preparation in the same glaucomatous eye on separate days. Both
clonidine solutions were effective in lowering the IOP; the 0.25% solution
was more effective than the 0.125% solution, and the former was slightly
less potent than pilocarpine. Pupil diameter was essentially unchanged in
all but one of the patients after clonidine. Pilocarpine reduced pupil
diameter in all patients. One eye treated with placebo also showed a
reduction in pupil size. Both systolic and diastolic blood pressure showed
a statistically significant reduction after clonidine, but the magnitude of
the change was small. We do not regard the minor blood pressure changes as
being a threat to the optic nerve but further studies in this aspect of
topical clonidine therapy are required.
