Background: Isoniazid is the most widely used anti-tuberculosis agent, yet it may lead to life-threatening complications. Case presentation: Here we report the case of a chronic hemodialysis patient who developed severe encephalopathy after the start of isoniazid. Blood levels of isoniazid were elevated, and acetyl-isoniazid over isoniazid ratio was decreased 3 h after intake of the medication, suggesting that a slow acetylator phenotype may have contributed to drug toxicity, in addition to pyridoxal phosphate removal by dialysis. This hypothesis was confirmed by sequencing of NAT2, the gene responsible for isoniazid elimination, and identification of NAT2 polymorphisms compatible with a slow acetylator phenotype. Isoniazid withdrawal along with supplementation using high doses of pyridoxine successfully reversed the drug toxicity. Isoniazid toxicity occurs in populations at risk, including patients with chronic kidney failure or NAT2 polymorphisms, who have a disturbed metabolism of pyridoxine or isoniazid, respectively, and those on renal replacement therapies, in whom pyridoxal phosphate -the active metabolite of pyridoxine -is inadvertently removed by dialysis. Conclusions: Physicians should be aware of the increased risk of isoniazid toxicity in patients on dialysis and in those with a slow acetylator phenotype conferred by NAT2 polymorphisms. Adaptation of prescription -either with higher doses of pyridoxine or decreased doses of isoniazid, respectively -has been suggested to reduce the risk of potentially life-threatening toxicity of isoniazid.

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Introduction Intravenous etomidate infusion is effective to rapidly lower cortisol levels in severe Cushing’s syndrome (CS) in the intensive care unit (ICU). Recently, etomidate treatment has also been proposed at lower doses in non-ICU wards, but it is not yet clear how this approach compares to ICU treatment. Methods We compared data from patients with severe CS treated with high starting doses of etomidate (median: 0.30 mg/kg BW/day) in ICU or with lower starting doses (median: 0.025 mg/kg BW/day) in non-ICU medical wards. Results Fourteen patients were included, among which ten were treated with low starting doses (LD) and four with high starting doses etomidate (HD). All patients had severe and complicated CS related to adrenal carcinoma (n = 8) or ectopic ACTH secretion (n = 6). Etomidate was effective in reducing cortisol levels below 500 nmol/L in a median of 1 day in the HD group compared to 3 days in the LD group (P = 0.013). However, all patients of the HD group had etomidate-induced cortisol insufficiency and needed frequent monitoring, while no patient from the LD group required hydrocortisone supplementation. No patient in either group died from complications of CS or etomidate treatment, but final outcome was poor as six patients in the LD group and all four patients in the HD group died from their cancer during follow-up. Conclusion Our study suggests that, for patients with severe CS who do not require intensive organ-supporting therapy, the use of very low doses of etomidate in medical wards should be considered.

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