Superficial necrolytic dermatitis in 11 dogs with a history of phenobarbital administration (1995-2002)

The clinical records of 11 dogs with histologically confirmed superficial necrolytic dermatitis (SND) and a history of phenobarbital (PB) administration (SND/PB) were evaluated retrospectively (1995-2002). Historical, clinical, clinicopathologic, ultrasonographic, and pathologic findings were compared with those in dogs with SND without prior PB exposure (SND/No PB; n = 9) and with those dogs with PB-associated hepatotoxicity without skin disease (PB/hepatotoxicity). Dogs in the SND/PB group accounted for 44% of all histologically confirmed cases of SND that were evaluated at The Ohio State University Veterinary Teaching Hospital between 1995 and 2002. Median age of dogs in the SND/PB group was 10 years, and median duration of PB therapy was 6 years. Mean alanine aminotransferase (ALT) activity was 239 U/L, and median duration of abnormally high ALT activity was 6.25 months before SND diagnosis. Plasma amino acid concentrations measured in 1 dog were severely decreased. Ultrasonographic findings of hypoechoic nodules with hyperechoic borders corresponded to pathologic findings of nodular areas of normal hepatic tissue surrounded by zones of collapsed parenchyma with vacuolated hepatocytes. Clinical, clinicopathologic, ultrasonographic, and pathologic features of SND/PB and SND/No PB were similar. PB-associated cirrhosis and overt hepatic failure were not features of SND/PB. Different pathogenic mechanisms might induce SND in dogs. Chronic administration of PB requires further examination as a potential risk factor for the development of SND.