Extracorporeal Clearance of Levetiracetam During Continuous Venovenous Hemofiltration in a Critically Ill Patient and New Dosing Recommendation

Pharmacokinetic considerations surrounding the use of levetiracetam for seizure prophylaxis in neurocritical care - an overview

INTRODUCTION

Levetiracetam (LEV) is one of the most widely used anti-seizure medications (ASMs) in clinical practice. This is due both to a different mechanism of action when compared to other ASMs and its easy handling. Indeed, because of its interesting pharmacokinetic properties, it is often used outside of the labelled indications, notably in the neurocritical setting as prophylaxis of epileptic seizures.

AREAS COVERED

A literature search was conducted and the most relevant studies on the pharmacokinetic properties of LEV were selected by two independent investigators. Current evidence on the use of ASM prophylaxis in the neurocritical setting was also reviewed, highlighting and discussing the strengths and limits of LEV as drug of choice for anti-epileptic prophylaxis in this scenario.

EXPERT OPINION

LEV has a "near-ideal" pharmacokinetic profile, which makes it an attractive drug for ASM prophylaxis in neurocritical care. However, current recommendations restrict ASMs prophylaxis to very selected circumstances and the role of LEV is marginal. Moreover, studies are generally designed to compare LEV versus phenytoin, whereas studies comparing LEV versus placebo are lacking. Further randomized trials will be needed to better elucidate LEV utility and its neuroprotective role in the neurocritical setting.

Levetiracetam dosing in patients receiving continuous renal replacement therapy

OBJECTIVE

The study was aimed to define appropriate levetiracetam dosing regimens from available published pharmacokinetics (PK) studies in critically ill patients with and without cirrhosis receiving continuous renal replacement therapy (CRRT) via Monte Carlo simulation (MCS).

METHODS

Mathematical pharmacokinetic models were developed using published demographic and PK data in adult critically ill patients with known variability and correlations between PK parameters. CRRT modalities (continuous venovenous hemofiltration and continuous venovenous hemodialysis) with different effluent rates were modeled. Levetiracetam regimens from available clinical resources were evaluated on the probability of target attainment (PTA) using pharmacodynamics (PD) target of the trough concentrations and area under the time-concentration curve within a range of 6-20 mg/L and 222-666 mg × hour/L for the initial 72 hours of therapy, respectively. Optimal regimens were defined from regimens that yielded the highest PTA. Each regimen was tested in a group of different 10,000 virtual patients.

RESULTS

Our results showed the optimal levetiracetam dosing regimen of 750-1000 mg every 12 hours is recommended for adult patients receiving both CRRT modalities with two different effluent rates of 25 and 35 mL/kg/h. Child-Pugh class C cirrhotic patients undergoing CRRT required lower dosing regimens of 500-750 mg every 12 ours due to smaller non-renal clearance. Of interest, some of literature-based dosing regimens were not able to attain the PK and PD targets.

SIGNIFICANCE

Volume of distribution, non-renal clearance, CRRT clearance, and body weight were significantly correlated with the PTA targets. Dosing adaptation in this vulnerable population should be concerned. Clinical validation of our finding is absolutely needed.

Levetiracetam pharmacokinetics in critically ill patients undergoing renal replacement therapy

PURPOSE

To determine clearance of levetiracetam in patients requiring continuous renal replacement therapy (CRRT) or sustained low efficiency dialysis (SLED).

MATERIALS AND METHODS

Adult patients with acute kidney injury or end stage renal disease requiring either CRRT or SLED and levetiracetam were eligible for inclusion. Simultaneous arterial, venous, and effluent samples for analysis of levetiracetam concentrations were collected every two hours for up to 6-8 h. Levetiracetam clearance (CL) and half-life (t_1/2) were calculated for each modality.

RESULTS

Eight CRRT patients and 4 SLED patients completed the study: 67% male, mean age 50 ± 13 years, and 83% had AKI. Seven CRRT patients received continuous venovenous hemodiafiltration (CVVHDF) [median pre-replacement rate 700 mL/h (range 500-1000), post-replacement rate 500 mL/h (range 200-1000), effluent rate 2500 mL/h (range 1700-3650) and delivered CRRT dose 27 mL/kg/h (range 19-54)] and one patient received CVV hemofiltration (CVVH). The mm mean levetiracetam CL during CVVHDF was 31.2 ± 8.5 mL/min, and the and the mean t_1/2 was 10.4 ± 2.2 h. For the patient requiring CVVH, clearance and t_1/2 were 22.5 mL/min and 9.5 h, respectively. Mean levetiracetam CL during SLED performed at a blood flow rate of 250 mL/min and a dialysate flow rate of 100 mL/min was 74.0 ± 25.3 mL/min and t_1/2 was 4.8 ± 2.3 h.

CONCLUSIONS

Levetiracetam clearance was substantial with both modalities under the operating conditions reported. There is the potential for subtherapeutic concentrations with current recommended dosing strategies that account only for kidney function and not these extracorporeal routes of elimination.

A Practice-Based, Clinical Pharmacokinetic Study to Inform Levetiracetam Dosing in Critically Ill Patients Undergoing Continuous Venovenous Hemofiltration (PADRE-01)

Limited data exist on the effect of continuous renal replacement therapy (CRRT) methods on anti-epileptic drug pharmacokinetics (PK). This prospective practice-based PK study aims to assess the impact of continuous venovenous hemofiltration (CVVH), a modality of CRRT, on levetiracetam PK in critically ill patients and to derive individualized dosing recommendations. Eleven patients receiving oral or intravenous levetiracetam and CVVH in various intensive care units at a large academic medical center were enrolled to investigate the need for dosing adjustments. Prefilter, postfilter, and ultrafiltrate samples were obtained before dosing, after the completion of the infusion or 1-hour postoral dose, and up to 6 additional time points postinfusion or postoral administration. Patient-specific blood and ultrafiltrate flow rates and laboratory values were also collected at the time of sampling. The average sieving coefficient (SC) for levetiracetam was 0.89 ± 0.1, indicating high filter efficiency. Six of the 11 patients experienced concentrations outside the reported therapeutic range (12-46 mg/L). The average volume of distribution was 0.73 L/kg. CVVH clearance contributes a major fraction of the total levetiracetam clearance (36-73%) in neurocritically ill patients. The average bias and precision of the estimated vs. observed total clearance value was ~ 10.6% and 21.5%. Major dose determinants were identified to be SC and effluent flow rate. Patients with higher ultrafiltrate rates will have increased drug clearance and, therefore, will require higher doses in order to match exposures seen in patients with normal renal function.

Levetiracetam Pharmacokinetics in a Critically Ill Anephric Patient on Intermittent Hemodialysis

BACKGROUND

In patients requiring hemodialysis, the extracorporeal circuit is expected to remove the majority of serum levetiracetam. The preferred levetiracetam dosing regimen in critically ill patients exhibiting complex pharmacokinetic profiles undergoing hemodialysis is unknown. The objective of this case is to describe levetiracetam pharmacokinetics in a critically ill anephric patient receiving intermittent hemodialysis.

METHODS

This is a case report of a single patient.

RESULTS

A 43-year-old anephric female was admitted to the intensive care unit for concerns of new onset seizure activity. She was loaded with 2000 mg levetiracetam followed by a 750 mg daily maintenance dose. The levetiracetam volume of distribution was 0.48 L/kg, and the interdialytic elimination half-life was 31 h. Hemodialysis removed nearly 85% of serum levetiracetam, and the patient exhibited slightly higher than expected non-renal elimination. Pharmacokinetic simulations identified 500 mg daily with 750 mg post-dialysis supplements as the regimen most likely to reduce variability in serum levetiracetam concentrations and achieve levels in the therapeutic range.

CONCLUSION

Substantial elimination of levetiracetam by hemodialysis occurred in this case, and non-renal clearance was slightly higher than in previous reports. Insufficient intradialytic or post-dialysis levetiracetam concentrations may place patients at risk of breakthrough seizures. This case indicates that dialysis patients on levetiracetam may require higher post-dialysis supplemental doses than currently recommended and tailored therapy supported by therapeutic drug monitoring.