No specific interaction studies have been performed with XALACOM (latanoprost and timolol maleate).
Patients who are receiving treatment with XALACOM and an oral beta-adrenergic blocking agent should be observed for potential additive effects of beta-blockade, both systemic and on intraocular pressure. The concomitant use of two topical beta-adrenergic blocking agents is not recommended.
There have been reports of paradoxical elevations in IOP following the concomitant ophthalmic administration of two prostaglandin analogs. Therefore, the use of two or more prostaglandins, prostaglandin analogs, or prostaglandin derivatives is not recommended.
The potential exists for additive effects resulting in hypotension, and/or marked bradycardia when timolol ophthalmic drops are administered with oral calcium channel blockers, catecholamine-depleting drugs or beta-adrenergic blocking agents, antiarrythmics (including amiodarone and quinidine), digitalis glycosides, parasympathomimetics, narcotics, guanethidineand monoamine oxidase (MAO) inhibitors.
Potentiated systemic beta adrenergic blockade (e.g., decreased heart rate, depression) has been reported during combined treatment with CYP2D6 inhibitors (e.g. quinidine, fluoxetine, paroxetine) and timolol.
Although XALACOM alone has little or no effect on pupil size, mydriasis has occasionally been reported when timolol is given with epinephrine.
Beta-adrenergic blocking agents 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 XALACOM. If such drugs are used they should be administered with an interval of at least 5 minutes between applications. Similarly, several contact lens soaking solutions contain thimerosal (see Drug-Lifestyle Interactions: Use of Contact Lenses).
Effects on ability to drive and use of machines: In common with other eye preparations, installation of eye drops may cause transient blurring of vision.
Use of Contact Lenses: XALACOM contains benzalkonium chloride which may be absorbed by contact lenses. Several contact lens soaking solutions contain thimerosal which may also form a precipitate with benzalkonium chloride (see Drug-Drug Interactions) Therefore, contact lenses should be removed before installation of the eye drops and may be reinserted after 15 minutes.