Spironolactone has previously been linked to cases of hypotonic hyponatraemia, but the specific accompanying biochemical signature in hospitalized patients—particularly when spironolactone is used with loop diuretics such as furosemide—has been underdescribed. This study aimed to characterize biochemical and epidemiological profiles of patients admitted with established hypotonic hyponatraemia according to spironolactone exposure.
The investigation was a single-centre retrospective cohort study of hospitalized patients with hypotonic hyponatraemia. Thiazide diuretic users were excluded. The primary comparison was between patients exposed to spironolactone (n = 107) and non-users (n = 427). Further subgroup analyses compared a spironolactone-alone subgroup (n = 27) with (i) a non-diuretic group (n = 374) and (ii) a spironolactone + furosemide group (n = 80).
Biochemical parameters examined included admission serum sodium (s-Na), serum potassium (s-K), serum urea (s-urea), serum uric acid (s-UA), serum creatinine (s-creatinine), and estimated glomerular filtration rate (eGFR). Urinary indices included fractional excretions such as FE-K, FE-Cl and FE-H2O. Correlations were performed between (a) admission s-Na and in-hospital mortality, (b) spironolactone dose and biochemical parameters (with and without adjustment for furosemide dose), and (c) s-K and relevant parameters.
Multivariable regression models were constructed with dependent variables that included s-K, s-Na, FE-K, FE-Cl, FE-H2O and s-urea to assess whether associations with spironolactone persisted after accounting for potential confounders.
The study cohort totaled 534 patients after applying inclusion criteria reported in the abstract. Key findings after adjustment for eGFR were:
Comparing subgroups:
On multivariable regression that accounted for measured confounders, spironolactone exposure remained independently associated with:
Notably, the observed increase in s-K associated with spironolactone use was not accompanied by findings consistent with reduced urinary potassium excretion in the analyses presented in the abstract.
The analyses did not identify clear evidence that concomitant furosemide materially altered the spironolactone-associated biochemical pattern in this dataset.
In hospitalized patients with established hypotonic hyponatraemia, spironolactone use was associated with a biochemical pattern characterized by higher serum potassium and higher serum urea, independent of eGFR and other evaluated covariates. The association with higher s-urea was quantitatively meaningful in the multivariable model (approximately a 24.5% increase).
The absence of a matching reduction in urinary potassium excretion in these analyses suggests that the mechanism of hyperkalaemia in this context may not be fully explained by simple decreases in urinary K+ loss as captured by the available fractional excretion metrics; however, the abstract does not provide detailed mechanistic data.
Because the pattern persisted after adjustment and was similar whether or not furosemide was co-prescribed, clinicians assessing hyponatraemic patients on spironolactone should be aware of the potential for concurrent increases in s-K and s-urea. This phenotype could aid bedside evaluation and differential diagnostic thinking in diuretic-associated hyponatraemia.
The abstract reports a retrospective single-centre design and provides summary statistical outcomes, but does not detail the study time frame, full inclusion/exclusion criteria beyond non-thiazide status, or the complete list of covariates included in each multivariable model. Information about causality, temporal relationships, or mechanistic investigations is not reported in the abstract.
The authors conclude that prospective studies are warranted to evaluate whether this biochemical pattern has diagnostic utility for identifying hyponatraemic patients receiving spironolactone. Future work should include predefined protocols for urinary studies, time-sequenced measurements, and broader adjustment for comorbidities and concurrent medications to clarify mechanisms and clinical application.
This retrospective cohort analysis found that spironolactone exposure in hospitalized patients with hypotonic hyponatraemia was independently associated with higher serum potassium and higher serum urea, a pattern not clearly altered by concomitant furosemide in the presented analyses. Prospective validation is needed to determine whether this biochemical signature can be used diagnostically in clinical practice.