Riesgo de sangrado en pacientes anticoagulados con antagonistas de la vitamina K que reciben antibióticos / Risk of bleeding in anticoagulated patients with vitamin K antagonists who receive antibiotics

Lograr un adecuado nivel de anticoagulación con antagonistas orales de la vitamina K suele ser un desafío frecuente en la práctica clínica, dado que su estrecho rango terapéutico suele verse afectado por diversas interacciones farmacológicas,alimentos y condiciones clínicas. A partir de un caso de un paciente anticoagulado que presenta una hemorragia gastro-intestinal posterior a realizar un tratamiento antibiótico, la autora de este artículo revisó la evidencia sobre el riesgo desangrado secundario a la interacción entre este tipo de anticoagulantes y antibióticos orales. Su conclusión tras realizar una búsqueda bibliográfica y seleccionar la mejor evidencia disponible, es que existe un aumento del riesgo relativo desangrado en pacientes anticoagulados que reciben antibióticos, por lo que deberían evitarse aquellos antibióticos con conocido potencial de interacción. Si ello no fuera posible, se recomienda monitorizar el estado de anticoagulación con dosaje de la razón internacional normatizada (RIN) posterior a la introducción del antibiótico. (AU)

Achieving an adequate level of anticoagulation with oral vitamin K antagonists is often a frequent challenge in clinical practice, given that their narrow therapeutic range is often affected by various drug interactions, food, and clinical conditions. Based on a case of an anticoagulated patient who presented gastrointestinal bleeding after antibiotic treatment, the authorof this article reviewed the evidence on the risk of secondary bleeding due to the interaction between this type of anticoagulants and oral antibiotics. Their conclusion, after performing a literature search and selecting the best available evidence, is that there is an increased relative risk of bleeding in anticoagulated patients receiving antibiotics, so antibiotics with known potential for interaction should be avoided. If it weren't possible, it is recommended to monitor the anticoagulation status with International Normalized Ratio (INR) dosing after the introduction of the antibiotic. (AU)

Predicción de la sensibilidad a la warfarina con base en polimorfismos de los genes VKORC1 y CYP2C9 en pacientes colombianos / Prediction of sensitivity to warfarin based on VKORC1 and CYP2C9 polymorphisms in patients from different places in Colombia

Introducción. La validación de los factores predictores de la sensibilidad a la warfarina es importante para evitar las hemorragias asociadas con la terapia anticoagulante. En los estudios previos hechos en Colombia con polimorfismos de los genes VKORC1 y CYP2C9 , se reportaban algoritmos con rendimientos diferentes para explicar la variación de las dosis, pero no se evaluaba la predicción de la sensibilidad a la warfarina. Objetivo. Determinar la exactitud del análisis farmacogenético de los polimorfismos *2 y *3 en el gen CYP2C9 y 1639G>A en el gen VKORC1 para predecir la sensibilidad a la warfarina en pacientes del Hospital Militar Central, un centro de referencia que atiende pacientes de diferentes lugares de Colombia. Materiales y métodos. Se recopilaron los datos demográficos y clínicos de 130 pacientes que habían recibido una dosis estable de warfarina durante más de dos meses. Se obtuvieron sus genotipos mediante un análisis de curvas de fusión , y, después de verificar el equilibrio de Hardy-Weinberg de los polimorfismos, se hizo un análisis estadístico con enfoque multivariado y predictivo. Resultados. Se construyó un modelo farmacogenético que explicó el 52,8 % de la variación de la dosis (p<0,001), solo 4 % por encima del rendimiento obtenido con los mismos datos usando el algoritmo del International Warfarin Pharmacogenetics Consortium . El modelo predictivo de sensibilidad logró 77,8 % de exactitud e incluyó como factores la edad (p=0,003), los polimorfismos *2 y *3 (p=0,002) y el polimorfismo 1639G>A (p<0,001). Conclusiones. Estos resultados en una población mestiza colombiana respaldan la validez de la predicción de la sensibilidad a la warfarina basada en los polimorfismos de los genes VKORC1 y CYP2C9.

Introduction: In the search to prevent hemorrhages associated with anticoagulant therapy, a major goal is to validate predictors of sensitivity to warfarin. However, previous studies in Colombia that included polymorphisms in the VKORC1 and CYP2C9 genes as predictors reported different algorithm performances to explain dose variations, and did not evaluate the prediction of sensitivity to warfarin. Objective: To determine the accuracy of the pharmacogenetic analysis, which includes the CYP2C9 *2 and *3 and VKORC1 1639G>A polymorphisms in predicting patients´ sensitivity to warfarin at the Hospital Militar Central , a reference center for patients born in different parts of Colombia. Materials and methods: Demographic and clinical data were obtained from 130 patients with stable doses of warfarin for more than two months. Next, their genotypes were obtained through a melting curve analysis. After verifying the Hardy-Weinberg equilibrium of the genotypes from the polymorphisms, a statistical analysis was done, which included multivariate and predictive approaches. Results: A pharmacogenetic model that explained 52.8% of dose variation (p<0.001) was built, which was only 4% above the performance resulting from the same data using the International Warfarin Pharmacogenetics Consortium algorithm. The model predicting the sensitivity achieved an accuracy of 77.8% and included age (p=0.003), polymorphisms *2 and *3 (p=0.002) and polymorphism 1639G>A (p<0.001) as predictors. Conclusions: These results in a mixed population support the prediction of sensitivity to warfarin based on polymorphisms in VKORC1 and CYP2C9 as a valid approach in Colombian patients.

Calidad de la anticoagulación oral con warfarina en una policlínica de cardiología: porcentaje de tiempo en rango terapéutico / Quality of oral anticoagulation with warfarin in a polyclinic of cardiology: percentage of time in therapeutic range

Introducción: la eficacia terapéutica y seguridad de la warfarina en prevención de trombosis en pacientes con fibrilación auricular (FA)/flutter y/o prótesis valvulares depende del adecuado nivel de anticoagulación, valorado mediante mediante la relación normalizada internacional o international normalized ratio (INR) (INR). El porcentaje de tiempo en rango terapéutico (TRT) valora la calidad de la anticoagulación con warfarina y se vincula inversamente con la incidencia de complicaciones trombóticas o hemorrágicas. Objetivos: valorar la calidad de anticoagulación oral con warfarina a través del análisis del TRT en la policlínica de cardiología. Identificar factores asociados a un adecuado nivel de anticoagulación (TRT ³ 65%). Material y método: estudio retrospectivo, observacional y analítico de una cohorte de 117 pacientes anticoagulados con warfarina entre el 1º de junio de 2012 y el 31 de julio de 2013. El TRT individual se calculó mediante método de Rosendaal (interpolación lineal). Las variables analizadas fueron: edad, sexo, indicación de anticoagulación, nivel de instrucción, grado de adherencia, situación familiar, comorbilidades y número de fármacos concomitantes. Resultados: la media de edad fue de 67 ± 14 años, sexo femenino 62%, anticoagulación por FA 63% y por válvula mecánica 37%. La media de TRT fue de 56,6%. Solo el 38% de los pacientes tuvieron una media de TRT adecuada (³ 65%) y esta se asoció de forma positiva a un rango etario entre 50-74 años (70,5%) (p = 0,04) y al uso concomitante de tres o más fármacos (79,5%) (p = 0,044). Conclusión: la media de TRT estuvo por debajo del nivel definido como adecuada calidad de anticoagulación. Una adecuada anticoagulación se asoció a menor edad y uso de tres o más fármacos. Estos resultados constituyen la base para el desarrollo de estrategias futuras para una mejor asistencia.

Background: the efficacy and safety of warfarin in preventing thrombosis in patients with atrial fibrillation/flutter or prosthetic valves depends on adequate anticoagulation levels expressed as INR (International Randomized Ratio). The percentage of time in therapeutic range (TTR) assesses the quality of warfarin anticoagulation and is inversely associated with the presence of thrombotic or hemorrhagic complications. Objective: to assess the quality of anticoagulation through analysis of TTR. Identify factors associated with an adequate level of anticoagulation (TTR³65%). Method: observational, retrospective and analytic study of a cohort of 117 patients anticoagulated with warfarin from June 1, 2012 to July 31, 2013. The individual TTR was calculated using Rosendaal method (linear interpolation). The variables analyzed were age, sex, indication for anticoagulation, level of education, degree of adherence, family status, comorbidities and number of concomitant drugs. X² test was used for statistical analysis of categorical variables. Result: mean age was 67 ± 14 years, 62 % were female and indication for anticoagulation was FA in 63% and mechanical valve in 37% of patients. The mean TTR was 56,6%. Only 38% had an adequate TTR and it was associated with age between 50-74 years (70.5%) (p=0,04) and concomitant use of 3 or more drugs (79.5%) (p=0,044). Conclusion: The mean TTR was below the value defined as good control. Better control was associated with younger age and use of three or more drugs. These results support the development of strategies for a better quality of assistance.

Analysis of Novel Anticoagulants for Atrial Fibrillation – Pharmacokinetics and Pharmacological Considerations.

Atrial Fibrillation (AF) is the most common arrhythmia. AF is a major risk factor for stoke. Warfarin has been available for more than 60 years and until recently it was the only oral anticoagulant used for the prevention of stroke. Despite the extensive studies and proven efficacy, its utility is limited by multiple factors. Warfarin interacts with a multitude of drugs and foods, has a delayed onset of action, has a narrow therapeutic range, requires routine lab monitoring and exhibits variable responses in patients. The novel agents dabigatran, rivaroxaban and apixaban have the potential to have some of the limitations of warfarin. This article will discuss the pharmacokinetic and pharmacological considerations and different characteristics of the novel anticoagulants when used for the prevention of AF.

Warfarin: pharmacological profile and drug interactions with antidepressants / Varfarina: perfil farmacológico e interações medicamentosas com antidepressivos

Oral anticoagulants are among the drugs with the greatest number of drug interactions. The concomitant use of several medications is a common practice in patients with cardiovascular problems, who often also present with depression; therefore, the probability of an interaction occurring between warfarin and the antidepressants is high, and may result in increased or decreased anticoagulant activity. Since the possible interactions between these two classes of drugs have been poorly explored in literature, with a risk to the patients who use them, we reviewed the pharmacology of warfarin and its possible interactions with antidepressants. Of the antidepressants analyzed, those that showed relevant effects on the interaction with warfarin were, in decreasing order: paroxetine, venlafaxine, fluoxetine, and duloxetine.

Os anticoagulantes orais estão entre as drogas com maior número de interações medicamentosas. O uso concomitante de vários medicamentos é uma prática comum em pacientes com problemas cardiovasculares, os quais frequentemente também apresentam depressão; assim, a probabilidade de ocorrer alguma interação entre a varfarina e os antidepressivos é bem expressiva, podendo resultar em um aumento ou uma diminuição da atividade anticoagulante. Como as possíveis interações entre essas duas classes de medicamentos se mostraram pouco exploradas na literatura, com risco aos pacientes que fazem uso delas, revisamos a farmacologia da varfarina e suas possíveis interações com antidepressivos. Dos antidepressivos analisados, os que apresentaram efeitos relevantes na interação com a varfarina foram, em ordem decrescente: paroxetina, venlafaxina, fluoxetina e duloxetina.

[Determination of the binding sites of propranolol HCLon bovine serum albumin by direct and reverse procedures]

To characterize the binding site of propranolol hydrochloride, the free concentration of warfarin [site-I specific probe] bound to BSA was measured upon the addition of propranolol hydrochloride. It was found that the free concentration of warfarin sodium was increased from 100% [as% of initial] to 552.35% when the ratio of propranolol to BSA was increased 1 to 6. In contrast, under the same experimental conditions, when diazepam was used as site-II specific probe, the increment of the free concentration of diazepam by propranolol was from 100% [as% of initial] to 415.42. From these data it is evident that the increment of free concentration of warfarin sodium is obviously greater than that of diazepam by propranolol. So it can be concluded that propranolol preferentially binds to site-I. Again as the displacement of Diazepam is quite enough it can be also suggested that propranolol in addition to site-I also binds to site-II on the BSA molecule but to a lower extent. Again in the reverse experiment, the free concentration of propranolol was increased from 100% [as% of initial] to 476% when warfarin to BSA ratio was 1 to 6 as shown, on the other hand, the free concentration of propranolol was increased from 100% [as% initial] to 222.39% when the ratio of diazepam to BSA was also 1 to 6. from the data it is clear that the increment of propranolol due to displacement by warfarin [Site-I probe] is higher than that of propranolol when displaced by diazepam [site-II probe]. Thus this reverse experiment also agrees with that of the previous experiment

Variantes de los genes CYP2C9 y apolipoproteína E en la respuesta individual a la warfarina / Variatins of gens CYO2C9 and apolipoprotein E in the induvidual response to warfarin

Introducción: la warfarina es el anticoagulante oral más usado en nuestro país y uno de los más usados a nivel mundial. Variantes polimórficas en varios genes influencian la respuesta individual a este fármaco, especialmente de CYP2C9 y de la apolipoproteína E. Nos proponemos estudiar la influencia en una población de pacientes uruguayos de estas variantes en la variabilidad interindividual en la respuesta a la warfarina y el riesgo de efectos adversos durante el tratamiento anticoagulante oral. Material y método: se incluyeron 55 pacientes en tratamiento crónico con warfarina. Se relevaron datos sobre dosis de mantenimiento, respuesta farmacocinética y efectos adversos. Se determinó el genotipo de los pacientes para las variantes *1, *2 y *3 de CYP2C9 y E2, E3 y E4 de apolipoproteína E. Resultados: los portadores de la variante *3 son los que requirieron dosis diarias de mantenimiento menores, seguidos por los portadores del alelo *2 y luego los homocigotos *1 (p=0,049). Los portadores de la variante *3 tuvieron también una mayor frecuencia de la tasa internacional normalizada (INR) por encima del rango deseado y requirieron más ajustes de dosis para lograr una adecuada anticoagulación; los eventos adversos fueron más frecuentes en los pacientes de genotipo *1/*3, tanto en relación al riesgo de sangrado como de sobreanticoagulación. La presencia del alelo E4 de la ApoE se asocia levemente a una mayor sensibilidad a la warfarina.Conclusiones: en el presente estudio, realizado en la primera población nacional proveniente de una policlínica de hipocoagulación, se confirma una mayor sensibilidad a la warfarina de los portadores de alelos variantes *2 y *3 de CYP2C9 y de la variante E4 de la ApoE, lo que puede tener importancia en la individualización de la dosis y los riesgos durante el tratamiento con este fármaco...

Introduction: warfarin is the most frequently used oral anticoagulant in Uruguay and worldwide. Polymorphic variants in various genes modulate individual response to this drug, especially CYP2C9. We studied the influence of these genetic variants on interindividual variability in response to warfarin and the risk of adverse reactions in an uruguayan population.Materials and methods: the study involved 55 patients undergoing chronic oral anticoagulant treatment with warfarin. Data on daily maintenance dose, pharmacokinetic response and adverse reactions was collected. CYP2C9 *1, *2 and *3, and Apoe E2, E3 and E4, genotype was determined by standard procedures.Results: carriers of CYP2C9 *3 allele required the lesser manteinance dose, followed by *2 allele carriers and then *1 homocygotes (p=0.049). CYP2C9 *3 allele carriers had more episodes of above de range International Normalized Ratio and required more dose adjustments to achieve a proper anticoagulation; adverse events were more frequent in patients with CYP2C9 *1/*3, regarding bleeding events as wells as overanticoagulation. Presence of ApoE E4 allele is associated with a moderately elevated sensibility to warfarin. Conclusions: this study is the first carried out on this subjet in an uruguayan population and confirms an increased sensibility to warfarin and risk of adverse effects in carriers of CYP2C9 *3 allele and in carriers of ApoE E4 variant, wich could be useful in warfarin dose and risk individualization during treatment with this drug. Genotypic data should be considered when establishing the best individual dose for individuals at high risk of bleeding, in those who suffered an adverse effect with this drug for physiopathlogic diagnosis and in young patients who underwent cardiac surgery who would potentially face a long term anticoagulant therapy. We will continue evaluating genomic components of risk during anticoagulation.