Article Reviews

Keratoconjunctivitis sicca (KCS) or dry eye

Keratoconjunctivitis sicca (KCS) or dry eye is a fairly common eye disease in dogs. The range of the 1997 to 2002 annual incidence rate was 0.800% to 1.039% in those veterinary teaching hospitals reporting data. Numerous causes, including drugs, have been identified. The most commonly reported drugs include sulfonamides, 5-aminosalicylic acid, and phenazopyridine. Non steroidal anti-inflammatory drugs (NSAID's) have also been associated with the development of KCS in dogs.

Etodolac (Fort Dodge Animal Health) is an NSAID that has anecdotally been associated with the development of KCS in dogs. The package insert lists KCS as an adverse event; an average of 28 KCS cases/year was reported to Fort Dodge from 1998 to 2002.

This is a retrospective study designed to identify the features and response to treatment of KCS in two groups of dogs that received oral etodolac. The sample population contained 65 cases obtained from the records of veterinary ophthalmologists and 146 cases reported to Fort Dodge Animal Health. A questionnaire was mailed to every individual reporting KCS and a telephone interview followed if needed. Various data was analyzed including breed, sex, weight, age, concurrent disease, dose and duration of treatment with etodolac, and treatment for KCS. Schirmer tear test values were collected to characterize the severity of KCS.

The results of the study failed to show a cause/effect relationship between the use of etodolac and the development of KCS. It did show that most dogs in both groups developed severe KCS with resolution occurring in a limited number. Dogs in the Fort Dodge Animal Health group were 4.2 times as likely to have a remission if the etodolac treatment period was less than 6 months as opposed to those with treatment periods greater than 6 months.

The authors state that this study was limited by the lack of a control group and suggest that a randomized prospective study is needed to identify the risk factors associated with the onset of etodolac associated KCS. A toxicological study including patient specific immunologic evaluation and histologic evaluation of the lacrimal glands is needed to determine the mechanism of action by which etodolac use results in the development of KCS in dogs.

Veterinarians should be aware of the potential for the development of KCS in dogs receiving oral etodolac. Schirmer tear tests should be performed prior to the onset of etodolac administration and periodically throughout therapy. Shorter durations of therapy may be associated with an improved outcome.