Is spironolactone effective for treatment-resistant hypertension?

How much does spironolactone actually lower blood pressure?

The short answer is: a lot, and consistently. In a 2025 randomized trial of 118 patients, adding spironolactone (12.5–25 mg daily) to a standard three-drug regimen lowered home-measured systolic blood pressure by an average of 14.7 mmHg over 12 weeks [1][3]. That's roughly the same effect as adding a completely new class of medication. A larger 2023 observational study of 515 patients found that 80% of those who added spironolactone achieved a clinic blood pressure below 140/90 mmHg, and 88% saw their systolic pressure drop by more than 10 mmHg [6]. These are not subtle improvements—they are the kind of changes that meaningfully reduce stroke and heart attack risk.

Spironolactone also works well in people who have not responded to other drugs. A 2024 study comparing spironolactone to eplerenone (a related drug) in 208 patients with true resistant hypertension found that 40.7% of those on spironolactone reached both clinic and 24-hour ambulatory blood pressure targets, compared to 33.3% on eplerenone [2]. The same study noted that spironolactone was particularly effective at lowering nighttime diastolic pressure, which is often the hardest to control. Across the studies here, the larger trials consistently show that spironolactone delivers a 10–15 mmHg drop in systolic pressure, making it one of the most potent add-on options available.

Does spironolactone protect your heart and kidneys beyond just lowering blood pressure?

Yes, and this is where spironolactone stands out. Several studies show it improves organ health in ways that go beyond the blood pressure number. A 2021 study using cardiac MRI in 30 patients found that after six months of spironolactone, aortic stiffness (measured by pulse wave velocity) dropped from 6.3 to 4.5 m/s, and this improvement was independent of blood pressure change [9]. That means the drug is directly making the large arteries more flexible, which reduces strain on the heart. Another MRI study from 2023 showed that spironolactone improved left atrial function and reduced the left atrioventricular coupling index—a measure of how well the heart's upper and lower chambers work together—again, regardless of whether the patient had high or normal aldosterone levels [10].

The kidneys also benefit. A 2022 study of 58 patients found that after one year on spironolactone, the urine albumin-to-creatinine ratio (a marker of kidney damage) dropped from 27.0 to 11.3 mg/g, and in those with moderate-to-severe albuminuria, it fell from 371.2 to 68.4 mg/g [11]. That's a dramatic reduction in protein leakage, which is a strong predictor of kidney failure. The same study also found that left ventricular mass index decreased by about 15 g/m², meaning the heart muscle was becoming less thickened—a sign of reduced strain. These effects are likely due to spironolactone blocking aldosterone, a hormone that directly damages blood vessels and promotes inflammation. In fact, a 2021 trial in patients with type 2 diabetes and resistant hypertension found that spironolactone lowered levels of the inflammatory cytokines interferon-γ and interleukin-6, suggesting it has anti-inflammatory actions that may contribute to organ protection [12].

What are the main risks, and who should be cautious?

The biggest concern with spironolactone is hyperkalemia—high potassium levels—especially in people with chronic kidney disease (CKD). In the AMBER trial, which included patients with resistant hypertension and advanced CKD (eGFR 25–45 mL/min), 64% of those taking spironolactone without a potassium binder developed a potassium level of 5.5 mmol/L or higher, and 23% had to stop the drug because of it [5][7]. However, when a potassium-binding drug called patiromer was added, the discontinuation rate dropped to 7%, and blood pressure lowering was still effective (about 11–12 mmHg systolic reduction) [5]. So the risk is real but manageable with monitoring and, if needed, a potassium binder.

Another common side effect is gynecomastia (breast tenderness or enlargement), which occurred in about 5% of patients in one study [2]. This is less common with the related drug eplerenone (about 2%), but eplerenone may be slightly less effective at lowering diastolic blood pressure [2][4]. A 2024 meta-analysis of six trials found no significant difference in blood pressure reduction between spironolactone and eplerenone, suggesting eplerenone is a reasonable alternative for those who cannot tolerate spironolactone's hormonal side effects [4]. For patients with very advanced kidney disease (stage 4, eGFR <30), a 2022 trial found that the thiazide diuretic chlorthalidone also works well, lowering 24-hour systolic blood pressure by 13.9 mmHg in the resistant hypertension subgroup, though it carries its own risks of hypokalemia and dizziness [8]. Overall, spironolactone is safe for most people with resistant hypertension, but anyone with reduced kidney function should have their potassium and kidney function checked regularly.

About These Sources

This answer is built on 12 peer-reviewed studies — published from 2021 to 2025, 4 from 2024 or later, 7 in Q1 journals, collectively cited 162 times — selected as the most relevant from 15 studies that passed quality screening, drawn from 47 papers retrieved from a database of over 500 million.

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