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The risks of severe leukopenia and agranulocytosis have varied over time and among geographical regions and cultures, with little information available on South American populations. Accordingly, we reviewed and analyzed data from a 6-year experience monitored by an Argentine national registry to which reporting of adverse events reports is required. We analyzed data for 2007-2012 from the pharmacovigilance program of the Argentine drug-regulatory agency (ANMAT) using standard bivariate and multivariate statistical methods and survival analysis. We identified 378 cases of adverse hematological events over 6 years among an average of 12 305 individuals/year treated with clozapine (308±133 mg/day) to estimate the mean annualized rates of leukopenia [0.19 (95% confidence interval [CI] 0.11-0.27)], neutropenia [0.38 (95% CI 0.34-0.43)], and agranulocytosis [0.05 (95% CI 0.02-0.08)] % per year [median latency 2 (95% CI 1.3-2.1) months]; fatalities related to agranulocytosis averaged 4.2 (95% CI 0.0-9.2) per 100 000 treated individuals/year. Factors associated significantly and independently with agranulocytosis were female sex, older age, and use of other drugs in addition to clozapine. With monitoring by international standards, recent risks of clozapine-associated agranulocytosis in Argentina were lower, but fatality rates were higher than that in other regions of the world. Risk factors include the use of multiple psychotropic drugs, female sex, and older age.

To rechallenge with clozapine for a patient who previously has experienced neutropenia or leucopenia or during clozapine treatment is a difficult clinical decision. Herein, we analyzed the results of such a rechallenge in 19 patients. We analyzed all the reports, from the database of the pharmacovigilance department of the Argentine National Administration of Drugs, Foods, and Medical Devices, of patients who were rechallenged with clozapine after a leucopenia or a neutropenia. Nineteen cases of rechallenge after leucopenia or neutropenia were reported between 1996 and 2014. One third of the patients re-exposed to clozapine developed a new hematologic adverse reaction. The second blood dyscrasia was less severe in 83% of the cases and had a shorter median latency as compared with the first (8 weeks vs 182 weeks, P = 0.0045). There were no significant differences for demographic and clinical characteristics of patients who developed a second dyscrasia as compared with those who did not. The present study shows that almost 70% of the patients rechallenged with clozapine after a leucopenia or a neutropenia did not develop a new hematological adverse effect, whereas the remaining 30% had a faster but less serious neutropenia.

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Resumen: En este artículo se proporciona un panorama general sobre la definición y notificación de los errores de medicación y los errores en el sistema de medicación en el contexto de 20 países de Latinoamérica. Se realizó una búsqueda en la literatura, considerando estudios de revisión y los