To Use or Not To Use (Opened Eye Medications)
Can you keep using those old eye drops and when should you throw them away? It is not the easiest question to answer but there are some guidelines.
Eye drops come in single use containers (small plastic vials with twist off caps) and in multiple dose bottles. The multidose bottles normally contain preservatives to prevent contamination. Frequently dropper tips touch the eyelids or countertops if you are not very careful. That point of contact can contaminate the bottle with bacteria. Preservatives are added to help overcome any inadvertent contamination. Preservative taken over the course of years can damage some of the surface cells on the eyes tissues and contribute to dry eye syndrome and red eyes. Preservative free single use eye drops have been developed to circumvent this problem, but they come with a hefty price tag.
Refrigerators And Eye Drops-Cool Or Not!
Most prescription eye drops are OK to use for 30 days after opening if they are kept refrigerated. Most bacteria are inhibited below 40 °F and above 140 °F. (The listeria bacteria that have been in the Colorado news of late are an exception since they thrive in cooler environments). Not only does refrigeration inhibit bacterial growth but it also helps maintain the stabilty of the drops and prevent them from degrading into other compounds. One study found the glaucoma eye drop Lumigan was much more stable than the well known xalatan drop at room temperatures. For people with glaucoma that spend frequent time traveling, eye doctors may prescribe an eyedrop like Lumigan when refrigeration is unlikely to be available. For about every 20 °:F rise in temperature drugs double in their instability. One thing to keep in mind is that refrigeration does not stop bacterial growth, it only slow it down. Prescription eye drops can become contaminated from bacteria inside of foods and refrigerators so it may not be the best choice for drops that are used only on a short term basis- and you should keep that thing clean anyway!
Who Knows What Really Lurks In Older Eye Medications-The Government And They Are Only Guessing!
Most prescription eye drops have a range of concentrations that are effective in killing bacteria. The potency of antibiotics is usually based on complex calculations that may not be accurate. A few drugs like tetracycline actually degrade to products that increase the resistance of bacteria to treatment. Determining shelf life is no easy task so the FDA tends to err a little on the conservative side. Eye institutions like Mooresfield Hospital in the UK frequently prepare unpreserved multiuse drops for special, severe eye infections. They have tested the sterility of these drops over the years and found that non preserved drops are typically safe to use for a week when refrigerated. Most studies indicate that multiuse preserved eye drops are good for 1 month after opening when refrigerated.
The rule of thumb is a week for non preserved multidose drops that are kept refrigerated and 30 days for preserved multidose drops that are kept refrigerated. A study of cycloporine, the same eye medicine found in restasis for dry eye treatment, also indicated 1 week when refrigerated. The formulation was slightly different, and restasis is approved as a single time use per vial. Some eye doctors allow their patients to use the same vial for 24-48 hours.
When you have opened eye drop prescriptions it is best to discard them after 30 days. As always, you should ask your prescribing optometrist first before using any eye medications in a manner that has not been through a formal approval and testing process. And clean that refrigerator!