Ciprofloxacin can (in rare cases) cause damage to the gastrointestinal tract. In some cases, cartilage damage has occurred, as well as crystalluria, which is the appearance of crystals in the urine. Long term use of Ciprofloxacin can result in a clouding of the lens inside the eye, or a cataract, as well as inflammation around the eye. Ocular side effects are especially frequent when used in cats, who are at risk of retinal damage and, in some cases, blindness. Cats should only take this drug with serious caution. In cases of and IV, rapid injection can lead to hypotension. Cats may also be at risk for symptomatic vomiting and muscle spasms of the colon, and a redness of their ears.