Before using it, tell your doctor or pharmacist if you are allergic to it; or to similar drugs (e.g., bimatoprost, latanoprost); or if you have any other allergies. This product may contain inactive ingredients (such as preservatives like benzalkonium chloride found in some brands), which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: eye problems (e.g., macular edema, iritis, uveitis, lens extraction/aphakia). Remove contact lenses before using this medication if your brand contains the preservative benzalkonium chloride. This preservative can be absorbed by contact lenses. Wait at least 15 minutes after using this medication before putting your lenses back in. If you are using another kind of eye medication (e.g., drops or ointments), wait at least 5 minutes before applying other medications. Use eye drops before eye ointments to allow the eye drops to enter the eye. Some products that may interact with this drug are: eyelash treatment (such as topically applied bimatoprost).