La hipertensión arterial resistente (HTAR) supone un importante problema de salud de manejo complejo. Este trabajo evalúa los riesgos y beneficios de añadir espironolactona para tratar la HTAR. Se evaluaron 216 pacientes con HTAR a quienes se añadió espironolactona (12,5-25mg/día) como antihipertensivo. Ciento veinticinco se analizaron retrospectivamente y 91 prospectivamente. Se analizaron parámetros de presión arterial (PA) y laboratorio (creatinina plasmática Creap, filtrado glomerular FGe y potasio plasmático Kp) al momento basal y tras 3-6-12 meses con espironolactona. Se objetivó una variación de PA sistólica/diastólica (media± desviación estándar) de −10,9±2,7/−4,3±1,6mmHg a los 3 meses y −13,6±2,8/−6,0±1,6mmHg a los 12 meses; p<0,001. Valores confirmados mediante monitorización ambulatoria de PA a los 12 meses. A los 3 meses, la Creap incrementó 0,10±0,04mg/dl, el FGe disminuyó −5,4±1,9ml/min/1,73m2 y el Kp incrementó 0,3±0,1mmol/l; p<0,001 para todos los casos. Estas variaciones se mantuvieron a los 12 meses. No hubo diferencias significativas en las variaciones de PA, Creap, FGe y Kp entre los 3 y 12 meses. Los resultados al analizar las cohortes retrospectiva y prospectiva por separado fueron superponibles. En la cohorte prospectiva, espironolactona fue suspendida en 9 pacientes (9,9%) por efectos adversos. Tras 3 meses con espironolactona se observó un descenso de PA asociado a descenso del FGe y aumento de Creap y Kp, cambios que se mantuvieron a los 12 meses. Espironolactona es un tratamiento eficaz y seguro para la HTAR en pacientes con FGe basal ≥30ml/min/1,73m2. Resistant hypertension (RH) is a significant health problem with complex management. The aim of this study was to evaluate the risks and benefits of adding spironolactone to treat RH. In total, 216 patients with RH in whom spironolactone (12.5-25mg daily) was added as an antihypertensive were evaluated. One-hundred and twenty-five (125) were analysed retrospectively and 91 prospectively. Blood pressure (BP) and laboratory parameters (serum creatinine sCrea, estimated glomerular filtration rate eGFR and serum potassium sK) were analysed at baseline and at 3-6-12 months after introducing spironolactone. A change of systolic/diastolic BP (mean±standard deviation) of −10.9±2.7/−4.3±1.6mmHg at 3 months and −13.6±2.8/−6.0±1.6mmHg at 12 months; p<0.001 was observed. These values were confirmed with ambulatory-BP monitoring at 12 months. At 3 months, an increase in sCrea of 0.10±0.04mg/dl, a decrease in eGFR of −5.4±1.9ml/min/1.73m2 and an increase in sK of 0.3±0.1mmol/l; p<0.001 was observed for all cases. These changes were maintained after 12 months. There were no significant differences in changes of BP, sCrea, eGFR and sK between 3 and 12 months. Results of the retrospective and prospective cohorts separately were superimposable. In the prospective cohort, spironolactone was withdrawn in 9 patients (9.9%) because of adverse effects. After 3 months with spironolactone, a decrease in BP associated with a decrease in the eGFR and an increase in sCrea and sK was observed. These changes were maintained at 12 months. Spironolactone is an effective and safe treatment for RH in patients with baseline eGFR ≥30ml/min/1.73m2.