Trifluridine behaves as a thymidine analog. It is phosphorylated and then becomes incorporated into the viral (and host to a lesser extent) genome in competition with thymidine triphosphate. This competitive incorporation, in addition to the inhibitory effect that this drug has on thymidylate synthetase, acts to halt viral DNA synthesis through chain termination.
Trifluridine is used in cases of herpes simplex 1 and 2 infections as a treatment for HSV keratoconjunctivitis. It is not effective in treating ocular infections due to herpes zoster, adenovirus, or vaccina virus.
Usage and Dosage
This drug is available in topical form and it can be applied directly to the infected eye because its biphasic solubility enables it to penetrate the cornea. It is available as a .1% solution and is administered every 2 hours during the time the patient is awake, or a 1% ointment that is applied five times daily. The maximum dosage over the course of the day is 9 drops. Usually, the infection will be halted and the epithelium will heal. Drug use can be discontinued after a course of 7 to 10 days.
Out of all the topical antiviral agents in use, TFT is the most specific and least toxic to corneal epithelial cells. The drug infrequently presents superficial punctate keratopathy due to toxicity. Resistance rarely develops to this drug. Other potential adverse effects include contact dermatitis, filamentary keratopathy, stromal edema, ocular irritation, and conjunctival scarring.
Leibowitz HM, Mbekeani JN. Corneal Disorders: Clinical Diagnosis and Management. W.B. Saunders Co. 1998. pg. 593-6.
Mauger, Craig. Havener's Ocular Pharmacology. Mosby-year book Inc. 1994. pg. 307-9.