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Re: Association of latanoprost with recurrent herpes simplex dendritic keratitis

I read with interest the article by Ekatomatis [1] on latanoprost treatment for primary open angle glaucoma causing herpes simplex dendritic keratitis. He should be applauded for reporting a serious side effect of latanoprost. His assertion however that latanoprost has been known to have almost no serious side effects is not entirely accurate. In fact, Wand et al [2] reported three patients who developed herpes simplex dendritic keratitis after therapy with latanoprost for primary open angel glaucoma. One patient with a previous history of herpes simplex keratitis had a recurrence while taking latanoprost, and resolved when latanoprost was discontinued. When rechallenged with latanoprost the patient again developed herpes simplex dendritic keratitis. A second patient with a history of bilateral herpes simplex dendritic keratitis had recurrence in both eyes on latanoprost treatment, confirmed on viral cultures, which only resolved on discontinuation of latanoprost and the start of antiviral treatment. When rechallenged with latanoprost therapy with concurrent prophylactic antiviral medication, the cornea remained clear. With discontinuation of antiviral suppression, herpes simplex dendritic keratitis recurred.

Using a rabbit model, Kaufman et al [3] have confirmed a relationship between latanoprost therapy and the recurrence and severity of herpes simplex keratitis. Latanoprost is a potent prostaglandin F2a analogue. Ekatomatis proposed biochemical disturbance of the surface of the cornea as a mechanism through which latanoprost causes recurrence of keratitis. It is more likely that prostaglandins, known to enhance the multiplication of herpes viruses [4], may be a common final pathway in herpes simplex keratitis recurrence. A multi-centre double blind case controlled study is required to clarify the side effect profile of this commonly used drug.

References
(1) Ekatomatis P. Herpes simplex dendritic keratitis after treatment with latanoprost for primary open angle glaucoma. Br J Ophthalmol 2001;85;1008-9.
(2) Wand M, Gilbert CM, Liesegang TJ. Latanoprost and herpes simplex keratitis. Am J Ophthalmol 1999;127:602-4.
(3) Kaufman HE, Varnell ED, Thompson HW. Latanoprost increases the severity and recurrence of herpetic keratitis in the rabbit (comment). Am J Ophthalmol 1999;127;531-6.
(4) Harbour DA, Blyth WA, Hill TJ. Prostaglandins enhance spread of herpes simplex virus in cell structures. J Gen Virol 1978;41:87-95.