Impact of high-flux haemodialysis on the probability of target attainment for oral amoxicillin/clavulanic acid combination therapy

Abstract Clearance of small molecules such as amoxicillin and clavulanic acid is expected to increase during high-flux haemodialysis, which may result in lower concentrations and thus reduced efficacy. To date, clearance of amoxicillin/clavulanic acid (AMC) during high-flux haemodialysis remains largely unexplored. Using published pharmacokinetic parameters, a two-compartment model with first-order input was simulated to investigate the impact of high-flux haemodialysis on the probability of target attainment (PTA) of orally administered AMC combination therapy. The following pharmacokinetic/pharmacodynamic targets were used to calculate the PTA. For amoxicillin, the time that the free concentration remains above the minimum inhibitory concentration (MIC) of ≥50% of the dosing period (≥50%ƒT >MIC ) was used. For clavulanic acid, the time that the free concentration was >0.1 mg/L of ≥45% of the dosing period (≥45%ƒT >0.1 mg/L ) was used. Dialysis clearance reported in low-flux haemodialysis for both compounds was doubled to represent the likely clearance during high-flux haemodialysis. Monte Carlo simulations were performed to produce concentration–time profiles over 10 days in 1000 virtual patients. Seven different regimens commonly seen in clinical practice were explored. When AMC was dosed twice daily, the PTA was mostly ≥90% for both compounds regardless of when haemodialysis commenced. When administered once daily, the PTA was 20–30% for clavulanic acid and ≥90% for amoxicillin. The simulations suggest that once-daily orally administered AMC in patients receiving high-flux haemodialysis may result in insufficient concentrations of clavulanic acid to effectively treat infections, especially on days when haemodialysis occurs.