Pharmacokinetics in Critically Ill Children with Acute Kidney Injury

Acute kidney injury (AKI) is a commonly encountered comorbidity in critically ill children. The coexistence of AKI disturbs drug pharmacokinetics and pharmacodynamics, leading to clinically significant consequences. This can complicate an already critical clinical scenario by causing potential underdosing or overdosing giving way to possible therapeutic failures and adverse reactions. Current available studies offer little guidance to help maneuver such complex dosing regimens and decision-making in pediatric patients as most of them are done on heterogeneous groups of adult populations. Though there are some studies on drug dosing during continuous renal replacement therapy (CRRT), their utility is in question because of the recent advances in CRRT technology. Our review aims to discuss the principles of pharmacokinetics pertinent for honing the existing practices of drug dosing in critically ill children with AKI, and the various complexities and intricate challenges involved. This in turn will provide a framework to help enable caretakers to tailor dosing regimens in complex clinical setups with further ease and precision.

Single and Multiple-Dose Kinetics of Ofloxacin in Patients on Continuous Ambulatory Peritoneal Dialysis (CAPD)

To evaluate the pharmacokinetics of ofloxacin, a novel quinolon antibiotic, in patients with end-stage renal disease (ESRO) on continuous ambulatory peritoneal dialysis (CAPO), we investigated 6 patients in a single-dose study and 9 patients in a multiple-dose study, all without peritonitis. In the single-dose study, patients received 200 mg ofloxacin orally. Serum concentrations (Cmax) peaked at 3.1 ± 0.3 mg/L (x ± SEM), 1.6 ± 0.5 h after p. 0. administration of the drug. Elimination half-life ( t112) was 26.8 ± 2.5 h. Peritoneal clearance accounted for 10% of the total body clearance. After 5- h dwell time, ofloxacin concentrations in the dialysate were 1.5 ± 0.2 mg/L, which is above the MIC90 for most bacteria responsible for peritonitis in patients on CAPO. In the multiple dose study, 200 mg ofloxacin were administered twice, with a time interval of 12 h, followed by 200 mg for 9 days every morning. Mean trough serum levels were 2.6 ± 1.0 mg/L, mean peak concentrations were 4.1 ± 1.7 mg/L. Mean ofloxacin concentrations in the peritoneal effluent were 1.9 ± 0.9 mg/L. It is concluded that an oral loading dose of 400 mg on the first day and a maintenance dose of 200 mg ofloxacin/day does not lead to significant accumulation, even though the elimination by the peritoneal route is only small. The proposed dosing regimen could be an adequate therapy of peritonitis and exit-site infections in patients on CAPO since levels reached in the dialysate effluent are bactericidal. The clinical usefulness in the treatment of peritonitis has to be proven in further studies.

Pharmacokinetics of Aztreonam Administered loP o in Continuous Ambulatory Peritoneal Dialysis (CAPD) Patients

The pharmacokinetics of Aztreonam (AZT) administered i.p. in six stable patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for end-stage renal disease (ESRD) were studied. One gram of AZT was added into a 2 L bag of dialysate (Medital-Bieffe®) just prior to infusion into the peritoneal cavity. The dwell time was 8 h. The serum maximum concentration of AZT was 42.5 ± 12.4 mg/L (x ± SD), achieved in 4.6 ± 1.0 h. The elimination half-life was 2.4 ± 0.8 h, almost equal to that found in normal subjects (1.7–2 h). The pharmacokinetic parameters of elimination, as elimination rate constant and clearance of AZT from peritoneal cavity were found 0.305 ± 0.101 h-1 and 10.05 ± 3.7 mL/min, respectively, while the bioavailability via the peritoneal mem brane was 90.8 ± 3.05% of administered dose.

It is concluded that AZT is eliminated from dialysate at a high rate after i.p. administration and its dialysate and serum levels exceed the MIC for the majority of sensitive organisms including Pseudomonas species. Aztreonam appears to be a potentially useful antibiotic for CAPD peritonitis.

Drug dosing consideration in patients with acute and chronic kidney disease-a clinical update from Kidney Disease: Improving Global Outcomes (KDIGO)

Drug dosage adjustment for patients with acute or chronic kidney disease is an accepted standard of practice. The challenge is how to accurately estimate a patient's kidney function in both acute and chronic kidney disease and determine the influence of renal replacement therapies on drug disposition. Kidney Disease: Improving Global Outcomes (KDIGO) held a conference to investigate these issues and propose recommendations for practitioners, researchers, and those involved in the drug development and regulatory arenas. The conference attendees discussed the major challenges facing drug dosage adjustment for patients with kidney disease. In particular, although glomerular filtration rate is the metric used to guide dose adjustment, kidney disease does affect nonrenal clearances, and this is not adequately considered in most pharmacokinetic studies. There are also inadequate studies in patients receiving all forms of renal replacement therapy and in the pediatric population. The conference generated 37 recommendations for clinical practice, 32 recommendations for future research directions, and 24 recommendations for regulatory agencies (US Food and Drug Administration and European Medicines Agency) to enhance the quality of pharmacokinetic and pharmacodynamic information available to clinicians. The KDIGO Conference highlighted the gaps and focused on crafting paths to the future that will stimulate research and improve the global outcomes of patients with acute and chronic kidney disease.

Multiple dose kinetics of ofloxacin and ofloxacin metabolites in haemodialysis patients

7 patients with end-stage renal disease on regular haemodialysis were treated orally with a loading dose of 200 mg ofloxacin and multiple maintenance doses of 100 mg per 24 h for 10 days. The pharmacokinetics of ofloxacin and its metabolites were studied at the end of the treatment period. Plasma and dialysate concentrations of ofloxacin and ofloxacin metabolites were measured by HPLC. Peak (3.1 mg.l-1) and trough levels (1.6 mg.l-1) and the AUC of ofloxacin were comparable to the values in healthy volunteers given 300 to 400 mg ofloxacin p.o. The mean half-life, determined in the dialysis-free interval (t1/2 beta) and during the haemodialysis session (t1/2 HD), was 38.5 h and 9.9 h, respectively. Extrarenal clearance (32.7 ml.min-1) was unchanged as compared to that reported in healthy volunteers after a single dose of ofloxacin. The fractional removal by haemodialysis amounted to 21.5%. Two metabolites, ofloxacin-N-oxide and demethyl-ofloxacin, were detected in plasma. Despite prolonged t1/2 beta of both metabolites (66.1 and 50.9 h) and multiple doses of ofloxacin the peak concentrations of the metabolites reached only 14% and 5% of that of the parent drug, respectively. It is concluded that in patients on regular haemodialysis treatment the dosage adjustment employed resulted in safe and therapeutically favourable plasma concentrations. The observed accumulation of ofloxacin metabolites does not appear to have any toxic or therapeutic significance.

Pharmacokinetics of antimicrobial agents in organ function impairment. A review

The pharmacokinetics of antimicrobial drugs in various types of organ function impairment are reviewed. The influence of renal function impairment on antimicrobial agents is well-known, although less is known about the accumulation of metabolites during renal failure. Fewer data are available on liver function impairment and more information is needed on highly metabolized agents. Pharmacokinetic studies in severely ill patients are urgently needed to investigate the influence of disease states on pharmacokinetics and to study the possibility of oral administration to seriously ill patients.