Objective: Taking the wrong medicine or medication error is a serious concern to patient safety.  The aim of this study was to statistically survey the relation between the placement of drugs on medicine shelf and the occurrence of error in taking a medicine.
Methods: The study comprised 2 groups.  The incident group contained 43 cases that were erroneously taken in the Obihiro Kosei General Hospital.  The control group contained 43 drug pairs matched by the similarity index of the drug names from among the drugs used in the hospital at random.  The similarity index of drug names was based on 10 quantitative indicators.  The distance of medicine shelf arrangement was represented by three variables: the horizontal distance, the vertical distance and the distance of shelf block.  Conditional logistic regression analyses of the occurrence of medication errors were performed by evaluating the three variables of the distance factor and their interaction for error in taking a similar-sounding named drugs.
Results: Conditional logistic regression analysis revealed that the vertical distance (OR: 0.64, 95%CI: 0.42-0.99) and the distance of the shelf block (OR: 0.74, 95%CI: 0.57-0.97) were significant risk-reduction factors of medication errors.  Four variables were extracted as the most suitable logistic regression model in terms of the interaction between them.  As the interaction between 3 variables (the horizontal distance, the vertical distance and the distance of shelf block) was significant (OR: 0.93, 95%CI: 0.86-0.99), they may be considered as synergistic risk-reduction factors.  Moreover, the horizontal distance was found to be a risk-enhancement factor (OR: 1.52, 95%CI: 0.93-2.48).
Discussion: In order to reduce the risk of medication errors due to similar-sounding drug names, placement of drug on the medicine shelf should take into consideration the three coordinates of the distance factor.

Autoimmune enteropathy (AIE) is a rare disease, characterized by intractable diarrhea, villous atrophy of the small intestine, and the presence of circulating anti-enterocyte autoantibodies. Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, and mutations in FOXP3, which is a master gene of regulatory T cells (Tregs), are major causes of AIE. Recent studies have demonstrated that mutations in other Treg-associated genes, such as CD25 and CTLA4, show an IPEX-like phenotype. We present the case of a 13-year-old girl with CTLA4 haploinsufficiency, suffering from recurrent immune thrombocytopenic purpura and intractable diarrhea. We detected an autoantibody to the AIE-related 75 kDa antigen (AIE-75), a hallmark of the IPEX syndrome, in her serum. She responded well to a medium dose of prednisolone and a controlled dose of 6-mercaptopurine (6-MP), even after the cessation of prednisolone administration. Serum levels of the soluble interleukin-2 receptor and immunoglobulin G (IgG) were useful in monitoring disease activity during 6-MP therapy. In conclusion, autoimmune-mediated mechanisms, similar to the IPEX syndrome, may be involved in the development of enteropathy in CTLA4 haploinsufficiency. Treatment with 6-MP and monitoring of disease activity using serum levels of soluble interleukin-2 receptor and IgG is suggested for such cases.