Levetiracetam pharmacokinetics and its covariates: proposal for optimal dosing in the paediatric population

OBJECTIVES

Levetiracetam is an anticonvulsive drug increasingly used in paediatric populations. Ontogenesis may alter its pharmacokinetics, demanding dose individualisation of levetiracetam in paediatric populations. We therefore aimed to explore levetiracetam pharmacokinetics and to propose its optimal dosing in the paediatric population.

METHODS

Individual levetiracetam pharmacokinetic parameters were calculated based on therapeutic drug monitoring data, using a one-compartmental model, and regression models were used to explore possible covariates.

RESULTS

56 patients aged from 47 days to 18 years were included in the analysis. The median (IQR) volume of distribution and clearance of levetiracetam were 0.7 (0.58-0.85) L/kg and 0.123 (0.085-0.167) L/hour/kg, respectively. Levetiracetam pharmacokinetics were influenced by postnatal age, body size descriptors and renal functional status.

CONCLUSIONS

Based on observed relationships, an individualised loading dose of 26.2 mg/kg body weight and maintenance dose of 20.7 mg/mL/min of estimated glomerular filtration rate were calculated as optimal. Since we observed increased levetiracetam clearance in association with valproate co-medication, caution should be used when combining these two drugs.

Pharmacokinetics and pharmacodynamics of clodronate disodium evaluated in plasma, synovial fluid and urine

BACKGROUND

Clodronate is a non-nitrogenated bisphosphonate approved for use in horses. There are no peer-reviewed published reports describing the pharmacokinetics or evaluating renal health indices and urinary excretion patterns in conjunction with plasma and synovial fluid concentration following the systemic administration of clodronate to horses.

OBJECTIVES

Describe clodronate concentrations in plasma, urine and synovial fluid and evaluate the effects on renal indices after intramuscular administration to healthy horses.

STUDY DESIGN

Experimental study with repeated measures.

METHODS

Six healthy adult horses received a single intramuscular dose of clodronate (1.8 mg/kg). Blood, synovial fluid and urine were collected prior to and after administration of clodronate up to 72, 48 and 168 hours respectively. Drug concentrations were measured using LC-MS/MS and noncompartmental pharmacokinetic analysis was performed. Renal function indices were also evaluated.

RESULTS

Clodronate was quantifiable for up to 24 hours in plasma and 48 hours in synovial fluid and detected at all time points in urine. Maximum plasma concentration of clodronate 210 ± 68.2 ng/mL occurred at approximately 34.8 ± 0.2 minutes after administration, while peak synovial concentration (57.7 ± 32.8 ng/mL) occurred at 2.67 ± 2.32 hours after administration and peak urine concentration (88 358.2 ± 79 521.4 ng/mL) occurred at 2.67 ± 2.58 hours post administration. Terminal half-life in plasma was 3.32 ± 1.25 and was 4.8 ± 3.05 hours in synovial fluid. Creatinine concentrations rose significantly after treatment but remained within normal adult reference ranges at all times.

MAIN LIMITATIONS

Limited number of animals and sampling times and the absence of urine collection for determination of concentration beyond 7 days.

CONCLUSIONS

Clodronate is rapidly cleared from the blood and synovial fluid. It has variable and biphasic urinary excretion. While significant increase in blood creatinine concentrations was present after a single intramuscular dose of clodronate, values were never above the normal reference range. Further studies are warranted in horses undergoing exercise and those undergoing multiple dosing schemes.