Viral keratitis herpes zoster

ANTIVIRAL AGENTS The antiviral drugs used in ophthalmology are summarized in Table 63-3 see Chapter 49 for more details about these agents). The primary indications for antiviral drugs in ophthalmology are viral keratitis, herpes zoster ophthalmicus, and retinitis. There currently are no antiviral agents for the treatment of viral conjunctivitis caused by adenoviruses, which usually has a self-limited course and is treated by symptomatic relief of irritation. 

Cytarabine is used to treat Burkitt s lymphoma and both myeloid and lymphatic leukemias. Its antiviral use is in the treatment of herpes zoster (shingles) infection (Table 43.3). It also is used to treat herpetic keratitis and viral infections resistant to idoxuridine. The drug generally is used topically, but it has been given by IV injection to individuals with serious herpesvirus infection (44). Cytarabine is deaminated rapidly in the body to an inactive compound, arabinosyluracil, which is excreted in... 

Vidarabine is used mainly in human HSV-1 and HSV-2 encephalitis, decreasing the mortality rate from 70 to 30%. Whitley et al. (57) reported that early vidarabine therapy is helpful in controlling complications of localized or disseminated herpes zoster in immunocompromised patients. Vidarabine also is useful in neonatal herpes labialis or genitalis, vaccinia virus, adenovirus, RNA viruses, papovavirus, CMV, and smallpox virus infections. Given the efficacy of vidarabine in certain viral infections, the U.S. FDA approved a 3% ointment for the treatment of herpes simplex keratoconjunctivitis and recurrent epithelial keratitis, and a 2% IV injection for the treatment of herpes simplex encephalitis and herpes zoster infections (Table 43.3). A topical ophthalmic preparation of vidarabine is useful in herpes simplex keratitis but shows little promise in herpes simplex labialis or genitalis. The monophosphate esters of vidarabine are more water-soluble and can be used in smaller volumes and even intramuscularly. These esters are under clinical investigation for the treatment of hepatitis B, systemic and cutaneous herpes simplex, and herpes zoster virus infections in immunocompromised patients. 

Vidarabine [vye DARE a been] arabinofuranosyl adenine, ara-A, adenine arabinoside) is one of the most effective of the nucleoside analogs and is also the least toxic. However, it has been supplanted clinically by acyclovir, which is more efficacious and safe. Although vidarabine is active against herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus (VZV), its use is limited to treatment of immunocompromised patients with herpes simplex keratitis or encephalitis, or VZV infections. Vidarabine, an adenosine analog, is converted in the cell to its 5 -triphosphate analog (ara-ATP), which is postulated to inhibit viral DNA synthesis. Some resistant herpes virus... 

Ocular antiviral chemotherapy in the horse is adapted from that used in herpes simplex virus (HSV) and varicella zoster keratitis in humans. The agents used are nucleotide analogs capable of inhibiting viral replication by competitive inhibition of the uptake of the nucleotide into the viral genome. These agents are virustatic and require an intact immune system to suppress or eliminate the virus from the eye. They probably do not eradicate any latent infection. The antiviral drugs available currently do not penetrate intact comeal epithelium and are poorly disseminated within the comeal stroma. The availability of these dmgs will vary in different countries and some may only be obtained from hospital pharmacies. 

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