Fatores associados às interações medicamentosas e aos eventos adversos a medicamentos em idosos com síndrome coronariana aguda em um hospital de ensino: aplicação da teoria do caos em situação de mundo real

Abstract

Drug interactions result in adverse reactions or ineffectiveness of pharmacotherapy, especially in elderly patients with polymedication with acute coronary syndrome. Thus, it is necessary to understand the potential for drug interactions in pharmacological prescriptions and the frequency at which they actually occur. Elderly patients, with serious illnesses and in an intensive care environment with the use of several drugs, typify a clear example of a Complex System, allowing a view based on the Chaos Theory and Complexity. Objective: The aim of this study was to identify the factors associated with potential drug interactions and adverse drug events during hospitalization of elderly patients and diagnosed with acute coronary syndrome in a teaching hospital within the focus of Complexity. Patients and Methods: This is a cross-sectional and descriptive study carried out at a teaching hospital in São José do Rio Preto, São Paulo, Brazil. The sample comprised 119 elderly patients. Data collection instrument adapted for the study was used. Potential drug interactions were identified and classified using computerized databases. Adverse events were characterized according to severity, temporal relationship, Naranjo's causality, classification of adverse drug reaction, interactions as a determining factor and traceability criteria. The statistical analysis used was descriptive. Results: The median age of the elderlies was 70 years, 66 (55%) were male. The median number of drugs per prescription was 11, with 76% of prescriptions showing excessive polypharmacy. Of the total elderlies studied, 30% had real drug interactions. The 5,348 potential drug interactions, in which patients were exposed, resulted in the occurrence of 53 real drug interactions. The median of actual drug interactions was the minimum of one and the maximum of three; 6% of patients who experienced real drug interactions had an outcome of death and 94% were discharged from hospital. Regarding the intensity of actual drug interactions, 64% were classified as moderate and 30% as major. The predominant mechanism of action was the pharmacodynamic (74%). In total 53 adverse events were identified, 53% moderate and 36% severe. Out of the adverse events, 11% occurred in two patients with death outcome, therefore, classified as lethal. All events were considered plausible according to the time relationship. Naranjo algorithm score classified 62% as a result of possible causality due to an adverse drug reaction, 23% probable and 15% defined causality. Adverse drug reactions were classified as: 55% Type B and 45% Type A. It was possible to graphically elaborate a network of diverse interactions characterizing the network of interactions as being a Complex System. Conclusion: This study showed a high frequency of potential drug interactions among hospitalized elderlies with acute coronary syndrome, although with a reduced frequency of real drug interactions when compared to the number of potential interactions. However, adverse reactions resulting from actual drug interactions occurred in one third of the sample. The high complexity of the System allowed inferring the possibility of the occurrence of several types of emergent behaviors.