Adverse effects of apraclonidine used in the diagnosis of Horner syndrome in infants.

Apraclonidine, a selective alpha(2)-agonist, was developed to lower intraocular pressure and minimize the systemic side effects associated with the use of its parent drug, clonidine.(1) An investigation of the site of action of apraclonidine incidentally uncovered a reversal of anisocoria in patients with absent sympathetic innervation of one pupil (Horner syndrome) due to its alpha(1)-effect on a pupil with denervation supersensitivity.(2) It has been used as a diagnostic test for Horner syndrome.(3,4) We report adverse effects of topical apraclonidine when used in the diagnosis of Horner syndrome in infants.