THERAPEUTIC FORUM

Cidofovir for Treating Adenoviral Conjunctivitis

by Christopher J. Quinn, O.D.

Viral conjunctivitis is one of the most common external diseases encountered by primary care clinicians. Most cases are caused by the adenovirus, which is a DNA virus that can also cause an associated ocular keratitis.

With more than 40 different serotypes, adenovirus is also a common cause of upper respiratory and gastrointestinal illness, and has been identified as the cause of pharyngoconjunctival fever (PCF) and epidemic keratoconjunctivitis (EKC).

Ocular Manifestations.
Typical ocular symptoms include the acute onset of conjunctival hyperemia in one eye, followed several days later by involvement of the other eye. Patients complain of foreign body sensation and a mucous discharge that often crusts on the eyelids upon awakening.

Most patients develop conjunctival follicles and preauricular lympha-denopathy. The conjunctiva can become highly injected, and petechial hemorrhages often form on the bulbar conjunctiva. Patients often describe having an upper respiratory infection before the onset of the conjunctivitis.

As the conjunctival symptoms improve, some patients develop corneal subepithelial infiltrates 10-14 days after the initial conjunctival infection develops. Corneal infiltrates can cause glare and loss of vision if the visual axis is affected.

Treatment.
Management of adenoviral conjunctivitis has been controversial. Currently available topical and oral antiviral agents are ineffective, and the bulk of current treatment is directed at providing the patient with symptomatic relief while the body fights the infection.

These treatments include cold soaks to reduce inflammation, and vasoconstrictors to relieve the associated conjunctival hyperemia.

The use of steroids in treating adenoviral infection has been controversial. They reduce the inflammatory response and can provide significant improvement in the patient's symptoms.

However, there is the potential for the patient to develop steroid-dependent subepithelial infiltrates, which then can recur once the steroids are discontinued. Steroids have other potential side effects when used chronically, such as increased intraocular pressure and cataract formation.

Another disadvantage to using topical steroids is the potential to exacerbate a herpes simplex infection, which can look very much like an adenoviral infection.

New therapy: With the possible approval of the antiviral agent cidofovir, currently used in treating CMV retinitis, we hope the debate over the best treatment for adenoviral eye infections will soon be settled.

Cidofovir works by interfering with DNA synthesis, thus preventing viral replication. It has a broad spectrum of activity against a wide range of DNA viruses, including the following: herpes simplex virus 1 and 2, varicella zoster virus, cytomegalovirus, Epstein- Barr virus, human pappiloma virus, adenovirus, and pox virus.

It also has a long duration of action, and the ointment form applied twice a day has been shown to be effective in treating adenoviral infections in an animal model. Cidofovir has also shown promise in treating herpes simplex epithelial keratitis.

In the meantime, until cidofovir is approved for treatment of adenoviral conjunctivitis, common sense should guide your treatment.

In patients with mild symptoms and no corneal involvement, the conservative approach is best. Use cold compresses and vasoconstrictors to provide symptomatic relief. Avoid using prophylactic antibiotics, as they are of little benefit and may actually increase the patient's risk of developing allergic or toxic reactions.
In patients who are highly symptomatic or who have developed corneal infiltrates that threaten vision, use a topical steroid to resolve the symptoms and/or infiltrates.