Pharmacokinetics of Colistin in an Adolescent Boy With Extensive Burn Injury:

Anti-infective Medicines Use in Children and Neonates With Pre-existing Kidney Dysfunction: A Systematic Review

Background

Dosing recommendations for anti-infective medicines in children with pre-existing kidney dysfunction are derived from adult pharmacokinetics studies and adjusted to kidney function. Due to neonatal/pediatric age and kidney impairment, modifications in renal clearance and drug metabolism make standard anti-infective dosing for children and neonates inappropriate, with a risk of drug toxicity or significant underdosing. The aim of this study was the systematic description of the use of anti-infective medicines in pediatric patients with pre-existing kidney impairment.

Methods

A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The EMBASE, Medline and Cochrane databases were searched on September 21st, 2021. Studies in all languages reporting data on pre-defined outcomes (pharmacokinetics-PK, kidney function, safety and efficacy) regarding the administration of anti-infective drugs in children up to 18 years with pre-existing kidney dysfunction were included.

Results

29 of 1,792 articles were eligible for inclusion. There were 13 case reports, six retrospective studies, nine prospective studies and one randomized controlled trial (RCT), reporting data on 2,168 pediatric patients. The most represented anti-infective class was glycopeptides, with seven studies on vancomycin, followed by carbapenems, with five studies, mostly on meropenem. Antivirals, aminoglycosides and antifungals counted three articles, followed by combined antibiotic therapy, cephalosporins, lipopeptides with two studies, respectively. Penicillins and polymixins counted one study each. Nine studies reported data on patients with a decreased kidney function, while 20 studies included data on kidney replacement therapy (KRT). Twenty-one studies reported data on PK. In 23 studies, clinical outcomes were reported. Clinical cure was achieved in 229/242 patients. There were four cases of underdosing, one case of overdosing and 13 reported deaths.

Conclusion

This is the first systematic review providing evidence of the use of anti-infective medicines in pediatric patients with impaired kidney function or requiring KRT. Dosing size or interval adjustments in pediatric patients with kidney impairment vary according to age, critical illness status, decreased kidney function and dialysis type. Our findings underline the relevance of population PK in clinical practice and the need of developing predictive specific models for critical pediatric patients.

Polymyxin B versus colistin: an update

Polymyxin B and colistin (polymyxin E) are polypeptide antibiotics that were developed in the 1940s, but fell into disfavor due to their high toxicity rates. These two antibiotics were previously regarded to be largely equivalent, due to similarities in their chemical structure and spectrum of activity. In recent years, several pertinent differences, especially in terms of potency and disposition, have been revealed between polymyxin B and colistin. These differences are mainly attributed to the fact that polymyxin B is administered parenterally in its active form, while colistin is administered parenterally as an inactive pro-drug, colistimethate. In this review, we summarize the similarities and differences between polymyxin B and colistin. We also discuss the potential clinical implications of these findings, and provide our perspectives on how polymyxins should be employed to preserve their utility in this era of multi-drug resistance.

Efficient removal of colistin A and B in critically ill patients undergoing CVVHDF and sorbent technologies

BACKGROUND

Colistin pharmacokinetics data are scarce regarding patients undergoing renal replacement therapy (RRT), or even absent as in patients treated with sorbent technologies potentially capable of removing colistin by extensive absorption on many polymeric materials.

METHODS

Twelve septic shock patients with acute kidney injury (AKI) undergoing RRT [continuous venovenous hemodiafiltration (CVVHDF) n = 7, coupled-plasma filtration adsorption-HF (CPFA-HF) n = 4, hemoperfusion n = 1] treated with colistin methanesulfonate at a dose of 4.5 × 10(6) U bid were studied. Colistin A (Col-A) and colistin B (Col-B) concentrations on plasma and effluent at time 0, 0.2, 1, 3, 6, 12, 24 and 48 h were determined by the liquid chromatography-tandem mass spectrometry method.

RESULTS

With CVVHDF the sieving coefficient was lower for Col-A, peaked early (0.40 for Col-A at 10 min, and 0.59 for Col-B at 3 h) and declined after 48 h (0.22 and 0.30 for Col-A and Col-B, respectively). Colistin's filter clearance showed a similar pattern, with the highest clearance value of 18.7 ml/min for Col-B at 1 h. With CPFA-HF after the cartridge the Col-A and Col-B levels were negligible (<0.2 mg/l) or not detectable. The sum of the effluent and cartridge clearances reached values of 30 and 40 ml/min for Col-A and Col-B, respectively. With hemoperfusion the postcartridge concentrations for Col-A and Col-B were about 30 % lower than those determined precartridge.

CONCLUSIONS

During CPFA-HF and CVVHDF, the extent of colistin removal is high, and patients should receive an unreduced dosage. However, due to risk of accumulation in long-term administration colistin plasma levels determination is recommended.

Intravenous colistin in a patient with serious burns and borderline syndrome: the benefits of therapeutic drug monitoring

Colistin is a decades-old drug that fell out of favour due to its nephrotoxicity. Today, colistin is experiencing a renaissance as a treatment against multiresistant Gram-negative bacteria such as Pseudomonas and Acinetobacter in critically ill patients. The optimal dosing of colistin for most infections is unknown. Here we present the intravenous dosing, optimised by therapeutic drug monitoring (TDM), of a borderline patient with severe burns and a consecutive transfemoral amputation. A 32-year-old woman with severe burns (35% total body surface area) and sepsis exhibited normal serum creatinine (SCr) concentrations at the beginning of her intensive care unit (ICU) stay, but over the course of her ICU stay her SCr increased to 100 μmol/L. With the colistin standard dose of 3 × 3 million units (MU) colistin/day after a loading dose of 9 MU, she failed to achieve effective plasma concentrations. The estimated glomerular filtration rate (eGFR) via CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) revealed GFRs between 180 mL/min and 63 mL/min after correcting for body surface. The patient required a high daily dosage of colistin (3 × 6 MU) that exceeded the approved maximum dose. Most clinicians rely heavily on SCr concentrations as the primary biochemical marker of GFR. At most, the CKD-EPI formula is helpful in determining creatinine clearance. The pharmacokinetics of colistin are currently poorly understood. TDM of colistin methanesulfonate and colistin may represent an invaluable approach to optimise colistin drug exposure in ICU patients with fluctuating renal clearance.

Colistin in burn intensive care: back to the future?

Colistin is a venerable antibiotic whose fortunes have been revived by its excellent activity, the diminishing output of novel clinically effective antibiotics and the increasing importance of MDR infection in burn surgery, both in the civilian and military arenas. This review synthesizes current evidence on the usage of colistin in burn surgery including the structure-activity relationship; dosing, pharmacokinetics/pharmacodynamic (PK/PD), analytic methods, resistance and current research efforts into the redevelopment of this antibiotic, to distil recommendations for future research and clinical efficacy.