<p>No specific interaction studies have been performed with this preparation. Patients who are receiving treatment with this preparation and an oral &beta;-adrenergic blocking agent should be observed for potential additive effects of &beta;-blockade, both systemic and on lntraocular pressure The concomitant use of two topical &beta;-adrenergic blocking agents is not recommended. Although this preparation alone has little or no effect on pupil size, mydriasis has occasionally been reported when Timolol is given with epinephrine. &beta;-blockers may increase the hypoglycemic effect of antidiabetic agents. In vitro studies have shown that precipitation occurs when eye drops containing thimerosal are mixed with Benzalkonium chloride, the preservative used in this preparatlon. If such drugs are used they should be administered with an interval of at least 5 minutes between applications. Similarly, several contact lens soakinq solutions contain thimerosal.</p>