Monitoring for valproate and phenytoin toxicity in hypoalbuminaemia: A retrospective cohort study

Abstract

Aims: Equations to calculate albumin-adjusted total concentrations have been validated to correlate with measured free concentrations for both phenytoin and valproate, but there is a lack of data to assess correlation with clinical outcomes. We aimed to assess the association of hypoalbuminaemia and albumin-adjusted total concentrations with concentration-dependent toxicity for phenytoin and valproate and review the impact on management decisions following concentration monitoring in hypoalbuminaemia. Methods: Patients undergoing concentration monitoring for phenytoin or valproate between January and December 2018 were included. Patients were identified using a centralised laboratory database with data extracted from medical records. Results: Total phenytoin concentrations were measured for 144 patients, with hypoalbuminaemia (≤30 g L−1) recorded in 59 (41%) patients. Albumin-adjusted phenytoin concentration >20 mg L−1 was associated with increased neurological adverse effects (77% vs. 43%, P 100 mg L−1 (49% vs. 23%, P