Original paper
A retrospective evaluation of adverse drug reactions of azathioprine in patients with autoimmunological skin diseases

Azathioprine (AZA) – immunosuppressive prodrug is characterized by a high interindividual variability in bioavailability and metabolism. It is used in a broad spectrum of dermatological dysimmune diseases, either as the primary drug or as adjunctive treatment. AZA undergoes non-enzymatic conversion in the liver yielding 6-mercaptopurine which afterwards is converted into cytotoxic 6-thioguanine nucleoside. It exerts immunosuppressive activity by inhibiting DNA replication during immune response. Moreover, it may also decrease proliferation of bone marrow cells which may lead to myelosuppression. Thus, the therapeutic role of AZA is often discussed because of toxicity. The study aims to characterize the toxicity profile of AZA. This study is based on retrospective examination of data taken from the hospital notes of these patients who had been treated with AZA due to dermatological dysimmune diseases. Of 294 patients evaluated, 151 were treated with AZA at a dose 50-200 mg/day. Adverse reactions (ARs) were reported in 12,6% of patients. Most of ARs occurred in patients aged between 20 and 29 years and during the first six months of treatment. Hematological toxicity occurred in 7 patients and deranged liver enzymes in 5 during the treatment with AZA. Gastrointestinal disturbances were reported by 6 patients. The pancreatitis was recognized in one patient. We conclude that azathioprine-induced toxicity should be diagnosed early and routine monitoring for its toxicity should include full blood count and liver function tests.