Understanding Trifluridine Side Effects

Trifluridine (brand name Viroptic) is an antiviral eye drop prescribed to treat herpes simplex keratitis — a viral infection of the cornea that can threaten your vision. Like all medications, Trifluridine can cause side effects. The good news is that because it's applied directly to the eye and has very little systemic absorption, most side effects are local and mild. Still, it's important to know what's normal and what warrants a call to your doctor.

What Is Trifluridine?

Trifluridine is a fluorinated pyrimidine nucleoside analogue — a type of antiviral medication that works by interfering with the DNA replication of herpes simplex virus. It's available as a 1% ophthalmic solution and is applied directly to the affected eye. For a more detailed overview, see our guide on what Trifluridine is and how it's used.

Common Side Effects

These side effects occur in a significant percentage of patients and are generally mild and temporary:

• Burning or stinging upon instillation (4.6% of patients) — This is the most frequently reported side effect. A brief burning sensation when you put the drop in is normal and usually lasts only a few seconds to a minute.
• Palpebral edema / eyelid swelling (2.8%) — Mild swelling of the eyelid around the treated eye.
• Superficial punctate keratopathy — Tiny, scattered defects on the surface of the cornea. Your doctor can see these during a slit-lamp exam. This is more likely with prolonged use.
• Epithelial keratopathy — A broader pattern of surface corneal changes, also related to the medication's effect on rapidly dividing cells.
• Eye irritation — General discomfort, itching, or a feeling that something is in your eye.
• Blurred vision — Temporary blurring immediately after instilling the drop. This typically clears within a few minutes.
• Eye redness (hyperemia) — Increased blood flow to the eye, causing a pink or red appearance.

Most of these side effects improve on their own and do not require stopping the medication. However, if any of them become severe or persistent, let your doctor know.

Serious Side Effects

Serious side effects from Trifluridine eye drops are uncommon, but they do occur. Contact your doctor promptly if you experience:

• Hypersensitivity reactions — Signs include severe eye swelling, hives, difficulty breathing, or a rash. These are rare but require immediate medical attention.
• Stromal edema — Swelling of the deeper layers of the cornea. Symptoms may include worsening blurred vision and a hazy appearance to your sight. This can indicate that the medication is affecting corneal health.
• Increased intraocular pressure — You may not feel this directly, but your doctor will check for it during follow-up visits. Symptoms could include headache, eye pain, or halos around lights.
• Keratitis sicca (dry eye) — Persistent dryness that doesn't resolve after the treatment course ends.

Trifluridine has no boxed warning from the FDA, which means there are no life-threatening risks that require special emphasis on the label.

Side Effects in Specific Populations

Children

Safety and effectiveness of Trifluridine have not been established in children under 6 years of age. For children 6 and older, the side effect profile is expected to be similar to adults, though close monitoring by a pediatric ophthalmologist is recommended.

Pregnant and Breastfeeding Women

Trifluridine is classified as Pregnancy Category C, meaning animal studies have shown some risk and there aren't adequate studies in humans. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Given the very small amount of drug absorbed systemically from eye drops, the actual risk is likely low — but this decision should be made with your doctor.

For breastfeeding mothers, Trifluridine is unlikely to be excreted in breast milk in meaningful amounts due to the very small dosage and its short half-life of about 12 minutes. However, discuss this with your healthcare provider.

Elderly Patients

No significant differences in side effects have been observed in elderly patients compared to younger adults.

How to Manage Common Side Effects

Here are practical tips for dealing with the most common side effects:

• For burning or stinging: Keep your Trifluridine refrigerated (36°F to 46°F) as directed. Cold drops tend to sting less. Close your eyes gently for a minute or two after instilling the drop.
• For blurred vision: Wait a few minutes before driving or doing activities that require clear vision. This is temporary.
• For eyelid swelling: A cool, clean compress applied to the closed eyelid for a few minutes can help reduce puffiness.
• For eye irritation or redness: Artificial tears (preservative-free) can be used between Trifluridine doses to soothe the eye. Wait at least 5 minutes between drops if using multiple eye medications.
• For surface corneal changes: These are typically detected by your doctor during follow-up exams. Treatment is limited to 21 consecutive days specifically to minimize the risk of corneal toxicity.

When to Call Your Doctor

Contact your eye doctor right away if you experience:

• Worsening eye pain or vision loss
• Severe swelling of the eye or eyelid
• Signs of an allergic reaction (rash, hives, difficulty breathing)
• No improvement after 7 to 14 days of treatment
• New symptoms that weren't present before starting the drops

Your doctor will likely schedule follow-up visits every few days while you're on Trifluridine to monitor healing and watch for side effects. Don't skip these appointments.

Final Thoughts

Trifluridine is an effective antiviral for herpes simplex keratitis, and most patients tolerate it well. The most common side effects — burning, stinging, and mild eye irritation — are temporary and manageable. Serious side effects are rare. The key is to follow your prescribed dosing schedule, attend all follow-up appointments, and never exceed 21 days of continuous use.

If you're having trouble finding Trifluridine at your pharmacy, check availability on Medfinder. For information on managing costs, see our guide on saving money on Trifluridine.