These drops may contain vasoconstrictors, which are medications that cause blood vessels to tighten. Making the blood vessels on the sclera smaller will whiten your eyes, but if you use red-eye removal drops regularly over time, you may need to use them more frequently to avoid the red eye from returning. The most common type of red-eye removal drop is called an alpha-adrenergic agonist. These work by reducing swelling and irritation to the eye caused by allergies or other problems within the eye. They can also be used to treat chronic conditions like glaucoma or cataracts. The two main types are parasympathomimetics and sympathomimetics. Parasympathomimetics include epinephrine and dipivefylate. Sympathomimetics include phenylephrine hydrochloride and methoxyphenamine hydrobromide (Mahanine). These drops should not be used by people who are also taking beta blockers because it is not known how they would react when used together at any dose. People who take adenosine monophosphate (Advil) or colchicine (Colcrys) should not take red-eye removal drops because they would be putting themselves at risk for developing kidney problems. Colchicine is also known as "the medicine for Alkies" because of its use in preventing attacks of gout and preventing recurrent strokes.