Trifluridine

The herpes virus is one of the main tiers of human viruses for which there is enough research and understanding that an antiviral drug can be made to help combat the infection. Trifluridine is one such antiviral drug, and its anti-herpesvirus properties allow it to be used mostly on the eye in order to help treat keratitis and keratoconjunctivitis.

Overview

Those are two inflammations of the eye that the herpes DNA virus can cause. Trifluridine is mostly seen in the form of eye drops, and that makes it a member of the ophthalmic class of pharmaceuticals. If the cornea becomes inflamed due to a herpes infection, or another virus, then this is known as epithelial keratitis. If the conjunctiva is involved in the inflammation as well (the lining inside the eyelids and on the white of the eye) then it is known as keratoconjunctivitis. In both cases, trifluridine is an antiviral drug that is given to a patient as eyedrops so that this condition can help to be alleviated. GlaxoSmithKline is the company that began to market it back in 1980 before a merger, but the drug is now handled by Monarch Pharmaceuticals and its trade name is Viroptic.

These eye drops have been seen to show good results when working on patients who have gotten the inflammation from either the herpes simplex virus type 1, herpes simplex virus type 2, or the vaccinia virus. As a substance, trifluridine is a white crystalline powder that is easily diluted in methanol or acetone.

Treated Conditions

  • Keratitis
  • Keratoconjunctivitis

Type of Medicine

  • White crystalline powder
  • Eye drops

Side Effects

The side effects that might be seen with trifluridine are some of the common ones that could manifest in any eye drop treatment: burning, local irritation, and stinging. Edema of the eye can also occur, and this might mean that that patient will see colored halos when around bright sources of irritating light. There could also be some allergic reactions because of the inactive ingredients that make up the solution, and so any allergies should be discussed with the prescribing doctor beforehand. Likewise, if any signs of an allergic reaction appear, then there should be immediate contact made with the physician to determine any further steps. The same is true if an application of trifluridine causes a change in eyesight, harsh eye pain, or an irritation that exceeds the mild susceptibility that is to be expected immediately after a drop is placed.

There have been some tests done that show a mutagenic potential with trifluridine. The activities that manifested were sometimes DNA-damaging or cell-transforming, but the tests were in vitro and the results are not understood well enough to say how the long-term effect on humans would present. The female rats that were exposed each day for a period of five days did show positive for some chromosome aberrations. There was also some clastogenic activity in Vicia faba cells during the tests.

Some of the tested rats also show a degree of oncogenic potential by having an increased rate of adenocarcinomas in their mammary glands and intestinal tract, as well as hemangiosarcomas and carcinosarcomas in various organs and glands. For this reason, it is important that the usage of the drug be only for the term necessary in order to relieve the symptoms so that the chance of long-term ill effects is reduced.

Dosage

The Viroptic ophthalmic solution comes in a 1% strength version, and one drop should be used on the cornea of the eye at an interval of about two hours while awake. A nine-drop limit is considered the threshold for daily application, and this regimen can be carried out until the corneal ulcer has healed or re-epithelialized back to normal. After that, the application can be reduced to a drop every four hours for another week. This extra application will help to ensure that everything is totally cleared. However, if the treatment does not seem to be working after the first week, then there needs to be a different type of treatment considered because the trifluridine will likely be ineffective. Also, it should not be given for more than three weeks at a time due to the chance of toxicity to the eye if the eye drops are used for too long.

Doses should not be missed when possible, and there need not be extra drops given due to the aforementioned possibility of toxicity to the eye in excess. One should wash their hands both before and after. Tilt the head back and pull down on the lower portion of the eyelid in order to form a crevice for the trifluridine to settle into. The eye, or eyes, should be kept closed for a couple of minutes with light pressure applied in order to help to keep the solution in the eye for the necessary amount of time for it to be effective. Any possible overdose or internal ingestion should be a reason to call medical control or consult with the doctor immediately. Patients should also avoid any type of sharing of the solution container because of the way that these herpes viruses are spread by contact with another. The drug seems to be suitable for both the pediatric and geriatric populations according to results seen so far.

Drug Interactions

Because of the way that the eye drops are applied, trifluridine usually leads to a very negligible amount of absorption, and so there are no studies that show that it would interact with any other drugs.

Warnings

The vision of a person may be temporarily blurred right after the trifluridine is put into the eye, and so there should be no driving, use of machinery, or any other type of activity that calls for complete and clear vision immediately after application. Some time should be taken until it is evident that such things can be performed safely. Pregnant women should only use the trifluridine eye drops when absolutely necessary due to the fact that it is unclear if there might be problems, although it seems highly unlikely.

Storage

The Viroptic solution comes in a plastic bottle, which doubles as a dispenser, and this should be kept in a refrigerated area at a temperature of between 2 and 8 degrees Celsius (36 to 46 degrees Fahrenheit). Patients should be careful not to allow the bottle to come into contact with anything that might contaminate the dispenser, and this includes the affected eye(s).

Summary

Because of the debilitating effects that can often be seen with the herpes keratitis infection, there generally has to be some sort of treatment therapy given in order to help the body clear itself of the complication. For that reason, trifluridine was approved for licensing by the United States Food and Drug Administration back in 1980. The ophthalmic brand was called Viroptic, and it has changed hands over the years having started its run at what was then known as Glaxo Wellcome and now being controlled by Monarch/King Pharmaceuticals. It can also be useful for the eradication of eye problems related to the vaccinia virus.

Since the Type I subvariety of the herpes simplex virus generally affects the face, there are more instances of people having it spread to their eye in this category. Type II is sexually transmitted and does not enter the eye quite as often.

However, the drug trifluridine is useful in either instance if a person is experiencing ophthalmic inflammation. The pharmacokinetics of trifluridine involves it passing through the cornea that it is applied to and being found in the patient's aqueous humour. There is not enough systemic absorption throughout any other region of the body for that to be impactful. The mechanism of action is understood such that the eye drop formulation of the medication is a nucleoside analogue that is similar enough to be incorporated into the viral DNA replication, but the drug has a fluorine group added, so that the base pairing is blocked. This interference is usually enough to cause the eye to be able to return to normal.

The basic aftermath is generally only relatively mild side effects such as eye irritation, burning sensations, stinging, some irritation, and perhaps edema, in rarer instances. Most of these side effects are well tolerated and transient so that the effect of the drug outweighs what must be endured. The non-profit group Cochrane is an organization in Britain that helps to organize medical research findings so that proper decisions can more easily be made by those who need to do so. Their Cochrane Systematic Review report states that trifluridine and aciclovir surpass the other available options (idoxuridine or vidarabine) in efficacy so that more people are healed in a two-week span using this drug instead of the others.

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Last Reviewed:
December 22, 2017
Last Updated:
December 22, 2017
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