Table 1_Association of different piperacillin/tazobactam ratios and dosages with the risk of hypokalemia: a propensity score-matched retrospective cohort study.xlsx

Reporting odds ratio (ROR), proportional reporting ratio (PRR), and corresponding 95% confidence intervals (95% CIs) were calculated to identify disproportionality signals; these measures were interpreted as reporting signals rather than incidence, clinical risk, or causality.</p>Results<p>A total of 1,825 patients treated with TZP were included. In the ratio comparison, 678 patients received TZP at a ratio of 8:1 and 716 received TZP at a ratio of 4:1.

In the dosage comparison, 678 patients received TZP 3.375 g q8h and 431 received TZP 4.5 g q8h. After 1:1 PSM, 1,356 patients were matched in the ratio groups, with 678 patients in each group, and the incidence of hypokalemia did not differ significantly (33.186% vs. 33.481%; P = 0.908). In the dosage groups, 862 patients were matched, with 431 patients in each group.

The incidence of hypokalemia was 33.643% in the TZP 3.375 g q8h group and 40.139% in the TZP 4.5 g q8h group (P = 0.048, χ² = 3.907). In FAERS, TZP (ROR = 3.809, PRR = 3.786, χ² = 71.205) and ampicillin (ROR = 5.326, PRR = 5.287, χ² = 58.414) met the prespecified criteria for positive hypokalemia disproportionality signals.</p>Conclusion<p>Within this TZP-treated cohort, the 8:1 and 4:1 component ratios were not associated with a detectable difference in hypokalemia incidence, whereas the 4.5 g q8h regimen was associated with a higher observed incidence than the 3.375 g q8h regimen after matching.

FAERS findings support the presence of hypokalemia reporting signals for TZP and ampicillin but do not establish comparative clinical risk or causality. These observations support careful serum potassium monitoring during TZP therapy, particularly with higher-dose regimens.</p>