Massive azathioprine overdose. Case report and review of the literature

Azathioprine and hydroxychloroquine overdose in Sjögren's syndrome patient with hypocalcemia: a case report

INTRODUCTION

Hydroxychloroquine and azathioprine have been routinely used to control and treat primary and secondary Sjögren's syndrome, which potentially triggered some overdoses by these drugs. Toxicity from hydroxychloroquine and azathioprine manifests in the form of cardiac conduction abnormalities, nausea, vomiting, and muscle weakness. Recognizing these unique drug overdoses and management of these toxicities is important. This case report aims to expand our current understanding of these drug overdoses and their management and also underscores the importance of anticipating and identifying fewer common complications, such as hypocalcemia.

CASE REPORT

A 34-year-old Persian woman with a history of Sjögren's syndrome presented to the emergency department 3.5-4 hours after an intentional overdose of hydroxychloroquine and azathioprine and severe hypotension and loss of consciousness. Although the patient was regularly taking other medications, such as fluoxetine, naproxen, and prednisolone, she explicitly clarified that these were not the substances involved in her overdose. Early investigations showed hypokalemia (2.4 mEq/L), hypocalcemia (7.5 mg/dL), and hypoglycemia (65 mg/dL). She was also diagnosed with metabolic acidosis and respiratory alkalosis. The electrocardiogram showed changes in favor of hypokalemia; other lab tests were run on the patient. Supportive treatments were applied, including rapid intravenous fluid dextrose 5%, normal saline, potassium chloride 30 mEq, and calcium gluconate 100 mg. The patient was managed and monitored overnight in the emergency room and recovered without residual side effects.

CONCLUSION

Hydroxychloroquine and azathioprine toxicity are considered rare, but it is likely to increase in frequency given the prevalence and increase in autoimmune diseases and the increasing usage of these drugs in treating such diseases. We found hypocalcemia as the presentation to this patient, which needs further investigation into the probable mechanism. Clinicians need to consider the unique effects of hydroxychloroquine and azathioprine poisoning and initiate appropriate emergency interventions to improve the outcomes in similar patients.

Acute thiopurine overdose: analysis of reports to a National Poison Centre 1995-2013

Literature regarding acute human toxicity of thiopurines is limited to a handful of case reports. Our objectives were to describe all cases of overdose with thiopurines reported to the Swiss Toxicological Information Centre between 1995–2013. A retrospective analysis was performed to determine circumstances, magnitude, management and outcome of overdose with these substances. A total of 40 cases (14 paediatric) were reported (azathioprine, n = 35; 6-mercaptopurine, n = 5). Of these, 25 were with suicidal intent, 12 were accidental and 3 were iatrogenic errors. The magnitude of overdose ranged from 1.5 to 43 (median 8) times the usual dose in adults. Twelve cases (30%) had attributable symptoms. The majority of these were minor and included gastrointestinal complaints and liver function test and blood count abnormalities. Symptoms were experienced by patients who took at least 1.5-times their usual daily thiopurine dose. Overdoses over two or more consecutive days, even if of modest size, were less well tolerated. One case of azathioprine and allopurinol co-ingestion over consecutive days led to agranulocytosis. Decontamination measures were undertaken in 11 cases (10 activated charcoal, 1 gastric lavage) and these developed fewer symptoms than untreated patients. This study shows that acute overdoses with thiopurines have a favourable outcome in the majority of cases and provides preliminary evidence that gastrointestinal decontamination with activated charcoal may reduce symptom development after overdose of these substances if patients present to medical services soon after ingestion.

Intentional overdose of azathioprine in a patient with systemic lupus erythematosus

A 14-year-old girl with systemic lupus erythematosus presented with a mixed overdose of paracetamol, ibuprofen and azathioprine (1500 mg) following a deliberate self-harm attempt. The patient was admitted and monitored. No adverse effects were observed. A review of the literature showed very few reported azathioprine overdoses. Lupus patients are at risk of developing low mood and depression (and related self-harm including overdose of medication). This can be as a consequence of the disease process itself or in reaction to the stresses of living with a chronic disease, which are perhaps particularly acute in some adolescents with the disease. An intentional overdose in a patient with lupus is clearly a cry for help and should be appropriately managed. Counselling of young people and their parents about possible mood disorders is an important part of the management of this chronic disease. Despite the theoretical risk of significant myelosuppression as well as other potential adverse effects, azathioprine in acute overdose seems to be generally well tolerated.

Azathioprine in the treatment of autoimmune blistering diseases

Although there are no standard guidelines for the treatment of autoimmune blistering diseases, azathioprine has shown good efficacy in acquired autoimmune blistering diseases, and is well tolerated. Side effects of azathioprine normally occur in mild variants. Severe reactions are due to reduced thiopurine S-methyltransferase (TPMT) or inosine triphosphate pyrophosphohydrolase (ITPA) activity. Therefore, screening for TPMT activity should be conducted in white patients and Africans, whereas Japanese should be screened for ITPA activity before therapy with azathioprine is started. Azathioprine is clinically meaningful for the treatment of pemphigus.

Azathioprine in dermatology: The past, the present, and the future

For several decades, dermatologists have utilized azathioprine to treat numerous debilitating skin diseases. This synthetic purine analog is derived from 6-mercaptopurine. It is thought to act by disrupting nucleic acid synthesis and has recently been found to interfere with T-cell activation. The most recognized uses of azathioprine in dermatology are for immunobullous diseases, generalized eczematous disorders, and photodermatoses. In this comprehensive review, the authors present recent advancements in the understanding of azathioprine and address aspects not covered in prior reviews. They (1) summarize the history of azathioprine; (2) discuss metabolism, integrating information from recent publications; (3) review the mechanism of action with attention paid to the activities of azathioprine not mediated by its 6-mercaptopurine metabolites and review new data about inhibition by azathioprine of the CD28 signal transduction pathway; (4) thoroughly examine thiopurine s-methyltransferase genetics, its clinical relevance, and interethnic variations; (5) review prior uses of azathioprine in the field of dermatology and grade the level of evidence; (6) discuss the use of azathioprine in pregnancy and pediatrics; review (7) key drug interactions and (8) adverse effects; (9) suggest a dosing and monitoring approach different from prior recommendations; and (10) explore the future of azathioprine, focusing on laboratory considerations and therapeutic application.

The impact of thiopurine S-methyltransferase polymorphisms on azathioprine dose 1 year after renal transplantation

Azathioprine metabolism is influenced by activity of the enzyme thiopurine S-methyltransferase (TPMT), which varies markedly between individuals. In this study we examined the influence of TPMT gene polymorphisms on azathioprine dose 1 year after renal transplantation. TPMT coding and promoter genotypes were determined using PCR-based assays. Azathioprine dose, white cell count, and intercurrent events throughout the first year after renal transplantation were ascertained from contemporaneous clinical notes. All patients analysed ( n=172) received an initial azathioprine dose of 1.5 mg/kg per day. Twelve individuals with one variant TPMT coding allele were detected (*3A n=11, *3C n=1). Of these, 58% required azathioprine dose reduction because of leucopenia, compared to only 30% of homozygous wild-type patients ( P=0.04). A significant correlation between the presence of >/=11 variable number tandem repeats (VNTRs) in the TPMT promoter and reduction in azathioprine dose was also identified ( P=0.001). We concluded that when azathioprine is administered at an initial dose of 1.5 mg/kg per day, both coding and promoter TPMT polymorphisms influence the dose tolerated.

Bile ductal and ductular changes of the livers in the renal allografted patients

Nine liver biopsies from six renal allografted patients suffering from liver injury were examined by light and electron microscope and immunostaining. The patients had never been on liver dysfunction prior to renal transplantation and after renal transplantation had been administered azathioprine continuously. These patients had shown HBs antigen negative sera. Three of these patients restored normal liver function after withdrawal of azathioprine. Accordingly, the liver diseases of the three were supposedly caused by azathioprine. The liver biopsies of six patients were histologically diagnosed as follows: chronic active hepatitis with severe cholestasis (1 patient), liver cirrhosis with cholestasis (1 patient), acute hepatitis (1 patient), and mild hepatitis (3 patients). The common pathological findings of six patients were degeneration of interlobular bile ducts and ductules, as well as degeneration of liver cells, and mild to moderate inflammatory cell infiltration of portal tracts and sinusoids. The degeneration of bile ductal and ductular cells were classified into two types: light microscopical finding showed vacuolar or eosinophilic cytoplasm and electron microscopic compatible findings showed hydropic cytoplasm scant of free ribosome and organelles, or dense cytoplasm rich in free ribosome and degenerated organelles. The basement membranes of interlobular bile ducts and ductules were always preserved.