Keratoconjunctivitis sicca in the dog following 5-aminosalicylic acid administration

1 Keratoconjunctivitis sicca (KCS) is an inflammatory eye condition, affecting the cornea and conjunctiva, caused by a deficiency in the aqueous fraction of tears. The condition is relatively common in the dog with a varied aetiology. A number of drugs have been implicated in the production of KCS in the dog including salicylazosulphapyridine (sulphasalazine). 2 This paper details clinically evident KCS in a 12-month oral toxicity study with 5-aminosalicylic acid (5-ASA), the therapeutically active metabolite of sulphasalazine. 3 The condition was first diagnosed at study week 22 and subsequently progressed both in incidence and severity. There was a distinct sex-difference in the response, with treated females being more affected than males. 4 There was a close correlation between the production of KCS and reduced lacrimation as assessed by the Schirmer tear test. 5 Although sulphasalazine causes KCS in dogs there have been no reports of ocular lesions of this type in man with this drug. It is highly probable that the dog is not a predictive model for man with regard to KCS induction by sulphasalazine or its metabolite 5-ASA.