Incidence and determinants of flucloxacillin-induced hypokalaemia

Abstract

Intravenous flucloxacillin is used to treat severe infections in hospitalized patients. Treatment with high dose intravenous flucloxacillin can lead to potentially life threatening hypokalaemia as adverse event. In this single-centre retrospective observational cohort study, we investigated the incidence and severity of hypokalaemia in patients treated with intravenous flucloxacillin. Furthermore, risk factors for flucloxacillin-induced hypokalaemia were identified. All patients treated for at least 48 hours with ceftriaxone or intravenous flucloxacillin and a normal baseline serum potassium level were included. The primary endpoint of the study was the incidence of hypokalaemia presented as the percentage of patients with a serum potassium measurement <3.5 mmol/L two to five days after initiation of antibiotic treatment. Logistic regression modelling was used to investigate the influence of sex and other risk factors on the development of flucloxacillin-induced hypokalaemia. In total 2290 patients treated with ceftriaxone and 452 patients treated with flucloxacillin were included. The incidence of hypokalaemia was 13.1% in patients receiving flucloxacillin. The incidence of moderate and severe hypokalaemia were respectively 1.3% and 0.2%. Identified risk factors for the development of hypokalaemia in patients treated with flucloxacillin were lower baseline potassium levels, older age and lower BMI. The incidence of hypokalaemia is increased in patients receiving flucloxacillin compared to patients receiving ceftriaxone. Healthcare providers should be aware of the risk for developing hypokalaemia in patients treated with intravenous flucloxacillin, especially in patients with risk factors.