Comparison of the efficacy of 0.03% tacrolimus eye drops diluted in olive oil and linseed oil for the treatment of keratoconjunctivitis sicca in dogs

Luís Felipe da Costa Zulim, Gisele Alborgetti Nai, Rogério Giuffrida, Carolina Silva Guimarães Pereira, Hugo Benguella, Aline Gutierrez Cruz, Bruna Toledo Duran Foglia, Aline da Silveira Batista, Silvia Franco Andrade

To compare the efficacy of 0.03% tacrolimus eye drops diluted in two different vehicles (linseed oil and olive oil) for the treatment of keratoconjunctivitis sicca (KCS) in dogs. This study included 60 dogs. Of this group, 20 were healthy and allocated to the control group, and 40 were diagnosed with bilateral KCS and randomly allocated to either the TO (tacrolimus in olive oil) or the TL (tacrolimus in linseed oil) groups. Ophthalmic examinations, Schirmer Tear Test-1 (STT-1), Tear Film Break-up Time (TBUT) and Fluorescein Test (FT) were carried out monthly, along with cytological and histopathological examinations at the beginning and end of the study. The clinical signs, corneal ulcers, Schirmer Tear Test-1 values, and Tear Film Break-up Time values improved in both groups after one month of treatment. Cytological examination at the end of the study showed decreased lymphocytes, neutrophil, metaplastic, and squamous cell counts in both groups, while the histopathological analysis showed decreases in lymphocytes and neutrophils and an increase in goblet cell density (cells/mm2). The decreases in neutrophil count were more significant (p<0.05) in the TL group for both types of examination. In sum, 0.03% tacrolimus eye drops diluted in olive oil and linseed oil were effective in the treatment of keratoconjunctivitis sicca. None of the evaluated parameters differed significantly between the two groups, except for neutrophil count which was significantly lower in the TL group. Thus, linseed oil may be considered as an alternative diluent for tacrolimus eye drops.