The Pharmacist's Rundown on Commonly Encountered Eye Drops
Steph’s Note: You’re at work, standing behind Mount Basket Everest waiting to be checked, and you see a number of them with little boxes inside. Not the Wegovy or Zepbound-sized boxes. (You already checked that stuff first because it made you feel good to be so productive so early.) These are little boxes, labeled like lovely pharmacy Christmas presents. Because you know that instead of having to twist off yet another bottle cap to check tablet imprints, you can check the NDC and expiration on the outside of the box and call it a day.
But…is that really all you should do? Do you actually know what you’re checking?
Sure, those little boxes of eye drops are quick, easy scripts to check to boost your quota numbers, but do you actually stop to think about these meds beyond them being the right product with the right patient?
Mmmhmm. I hear you.
That’s why today, we’re here to give you the quick rundown on what you need to know about the most commonly encountered eye drops. So you can give those scripts a little more TLC.
Pearls about Medicated Eye Drops
Before we get into the different types of eye drops, let’s talk about these meds in general. There are a couple pearls you should log away (NAPLEX question alert!).
First, as a general rule of thumb, many eye drops can be used in the ears as well. Eye drops are formulated to be gentle and non-irritating to ophthalmic tissues, and they are sometimes used in the ears due to cost or availability. BUT the reverse isn’t true. When ear drops are accidentally instilled in the eyes, they can cause significant burning and pain! (Image)
So be sure to pay close attention to a prescription’s sig, especially whether it says “optic” vs “otic.” And gasp! Sometimes you still get scripts with abbreviations like “OD,” “OS,” and “OU.” As much as you may want to avoid learning those shorthands (because they really shouldn’t be in use anymore with computerized order entry), they are still used. Frequently. I can’t tell you how many times I receive an electronic script with these abbreviations…smh.
As tempting as it may be to think that the “O” stands for “otic,” throw that out the window now. That “O” actually stands for the Latin “oculus,” meaning…you guessed it…eye. Here’s the list for you visual folks:
OU = oculus uterque = both eyes
OD = oculus dexter = right eye
OS = oculus sinister = left eye
Ok, so eye drops in the ears may be a yes. Ear drops in the eyes are a NO.
Now that we have that straight, let’s move on to the next pearl. When you receive a script for eye drops, it’s up to you to determine the days supply of the product you’re dispensing. Normally, this calculation is super easy (e.g., 14 tabs of amox/clav given twice a day = a 7 days supply). However, when the sig is written in drops and the product is dispensed in milliliters, you gotta know one more crucial bit of info.
While there is some variance depending on the medication’s viscosity and the size of the dropper, it is generally accepted that there are 20 drops to 1 milliliter. Another way of looking at this (if you do the math) is that 1 drop is about 0.05 milliliter. Whichever way is easier for you to remember is dandy, just log that away.
Armed with this tidbit, calculating the days supply of an eye drop product becomes much easier. Let’s say you have a script for prednisolone ophthalmic suspension with directions to instill 1 drop in both eyes 4 times a day. It’s a 5 milliliter bottle. That means the patient will use 8 drops/day, which is approximately 0.4mL/day. So the 5mL bottle should last 12.5 days. Voila, you have your days supply (and you can also make sure the patient will have enough for the intended treatment duration!).
Counsel your contact lens-wearing patients that they may have to locate their backup glasses while using medicated eye drops.
Moving on, this is a common question from patients picking up eye drops. “Can I use this with my contacts?”(Image)
Overwhelmingly, the answer is, “No.”
Unless a product is specifically labeled for use while wearing contact lenses (usually a rewetting product), contacts should be removed before using medicated eye drops because they can be damaged by the eye drops. Patients should wait at least 15 minutes after their last eye drop before putting contacts back in.
Let’s get to the drugs now.
Antibiotic Eye Drops
Ophthalmic antibiotics encompass a variety of drug classes and may be single or combination products. As you can imagine, they are used to treat bacterial infections of the eye and eyelid. The ones we see the most include the following:
Discard the remaining product. Just do it. Don’t hesitate. Don’t think to yourself that you’re gonna need it in case the infection comes back. It will become the infection.
Key points to remember with antibiotic eye drops will likely sound very familiar to you. Finish the full course of therapy to prevent half-treated infections and bacterial resistance. Discard any remaining product (rather than hanging on to it to self-treat later). (Image)
This is especially important when it comes to eye drops since the product can become contaminated if a patient accidentally touches their eye with the dropper…and then when they pull it out of the cabinet or fridge to use it again 6 months later, badness. Just badness.
Moving on…
Steroid Eye Drops
Next, we have the corticosteroids. Just like with their systemic counterparts, ophthalmic steroids are used to reduce inflammation. This may manifest as eye swelling, redness, and/or irritation, and it could be caused by anything from wearing contact lenses too many days - and nights - in a row (ahem, my younger self wouldn’t know aaaaaanything about this…) to post-surgical to allergies to uveitis to chemical injuries.
Also like their systemic cousins, ophthalmic steroids come with a slew of possible issues. These include cataracts, glaucoma (secondary open-angle), secondary infections, and delayed healing. So choosing an appropriate potency product, using for enough time to quiet down the inflammation, and tapering off are all important tenets of therapy.
Intraocular pressure (IOP) can also be monitored if a patient requires prolonged topical steroids, especially high potency medications. Interestingly, the risk of increased IOP with ophthalmic steroids is significantly increased (5% vs 90%) in patients with a family history of glaucoma, so inquiring about family history is a useful risk stratification tool for devising monitoring strategies.
The Glaucoma Team
Contrary to the plethora of memes that make glaucoma seem easy breezy (Image), it’s actually a very scary - and scarily common - umbrella of diseases. There are 2 types of glaucoma: open-angle (the most common type) and closed-angle (or angle-closure) glaucoma. Regardless of type, the main issue in glaucoma is increased intraocular pressure (IOP) due to an imbalance in aqueous humor production vs drainage. High IOP damages the precious optic nerve. Optic nerve damage, if left unchecked, eventually leads to blindness.
As one of the leading causes of blindness in people over the age of 60, glaucoma sounds like a great space for pharmacists to learn more and improve patient care, right?
That’s why we’re here! On to the medications!
Topical (ophthalmic) therapies for glaucoma focus on decreasing IOP. They do this in 2 ways:
Decrease fluid production in the eye, or
Improve fluid drainage out of the eye.
Let’s take a closer look at these 2 mechanisms and the drugs that produce these effects.
When it comes to how these medications are used, typically patients are started on a single agent (often a prostaglandin given their relatively low risk of systemic adverse effects). If IOP lowering is insufficient, agents from different classes may be added on for increased effect.
How much do these agents lower IOP? Good question!
In addition to cost and number of times per day they must be used, medications are selected for individual patients based on their local and systemic effects. We’ve already mentioned that the prostaglandins are highly utilized early in therapy due to their tolerability and low risk of systemic effects, but let’s take a moment to compare local and systemic effects of these agents:
They can all cause local burning and stinging, surprise surprise. But yes, you read that earlier sentence correctly. There absolutely can be systemic absorption and effects from eye drops! So just because it’s being applied to the eye doesn’t mean that it’s benign for the rest of the body, especially the beta blockers.
I’m not sure why it’s tempting to think of the eye as isolated from the other organ systems (or maybe that’s just my brain’s way of thinking), but don’t fall into this trap. The eye can be a systemic medication portal too.
Many of these medications are also available in combination products to improve adherence. Speaking of adherence, you wouldn’t think it would be too bad to do an eye drop in both eyes once or twice a day, would you? So why do we worry about adherence so much with these glaucoma regimens?
Well, think about it like this. Patients are supposed to wait at least 5 minutes between eye medications. Consider the patient who is on 2-3 of these eye drops. That’s waiting 5-10 minutes several times a day to do multiple doses. Consider how long it takes you to pop that multivitamin just once a day and how often you miss a dose…and that’s just a quick down the tube! Even an albuterol inhaler only requires waiting a minute between puffs, and people don’t even like to do that!! So how often do you think people actually wait the 5 minutes between eye drops…
This seems to appropriately summarize our current patience level.
Mmmhmm. We’re not exactly a patient society. (Image) So the more combination products patients can use, the fewer the rounds of eye drops, and the less waiting.
Voila, there you have it! The members of the glaucoma eye drop team, lowering IOP and (ideally) glaucoma diagnoses one drop at a time.
The tl;dr of Eye Drop Medications
This post is certainly far from all-inclusive, but hopefully you’ve taken away some ophthalmic knowledge that you didn’t have previously. Now when you encounter those little labeled pharmacy Christmas present boxes at the pharmacy - or when you’re reviewing a patient’s home medication list in the hospital - you will be better informed to do more than just check that NDC number.
A few key takeaways about eye drops:
Beware abbreviated sigs and be sure that the product chosen makes sense for use in the eyes. Remember, eye drops may be used in the ears, but the reverse is not true!
Patients should remove contact lenses for eye drop administration and wait 15 minutes before putting contacts back in after instilling drops. Wait 5 minutes between eye drop medication applications.
For conversions, 20 drops = 1 milliliter.
Antibiotic eye drops come in a variety of mechanisms, and counseling points are similar to their oral counterparts. Finish the full course, and know that systemic exposure is possible.
Steroid eye drops are also reminiscent of their systemic cousins, especially as pertains to their plethora of adverse effects. Choose wisely when it comes to potency and duration of therapy to avoid undesirable consequences.
Topical glaucoma medications either increase fluid outflow or decrease fluid production with the goal of decreasing intraocular pressure (IOP) and preserving the optic nerve. Systemic adverse effects, cost, and frequency of use may dictate the order in which these medications are used.