Determination of vancomycin and gentamicin clearance in an in vitro, closed loop dialysis system

Background\ud The purpose of this study was to evaluate the feasibility of utilizing an in-vitro, closed loop hemodialysis system as a method to assess drug clearance. Secondarily, this study tested the influence of variables (blood flow rate, dialysate flow rate, and type of filter) in the hemodialysis procedure on the clearance of vancomycin and gentamicin.\ud \ud Methods\ud An in-vitro, closed loop hemodialysis system was constructed. The vancomycin (30 mg/L) and gentamicin (25 mg/L) were added to a simulated blood system (SBS). Four conditions (C1-C4) were tested by defining the filter (Polyflux 170H or F180) and the blood and dialysate flow rates (BFR and DFR). All hemodialysis sessions were 3 hours in length and each condition was completed in duplicate. Dialysate effluent was collected in a 50 gallon polyethylene drum. Samples were collected (in duplicate) from the SBS and the dialysate effluent at baseline and at the end of the hemodialysis session. Samples were analyzed for vancomycin and gentamicin with an ultrahigh performance liquid chromatography/tandem mass spectrometry method.\ud \ud Results\ud A total of eight 3-hour hemodialysis sessions were conducted. For all tested conditions (C1-C4), vancomycin was undetectable in the SBS at the end of dialysis. However, total vancomycin recovery in the dialysis effluent was 85±18%, suggesting that up to 15% may have adsorbed to the dialysis filter or tubing. Gentamicin clearance from SBS was >98% in all tested conditions. Average gentamicin recovery in the dialysate effluent was 99±15%.\ud \ud Conclusion\ud Both vancomycin and gentamicin were readily removed by high-flux hemodialysis under all conditions studied. No significant differences in drug clearance were observed between conditions used in this in vitro study. The clinical implications of changing these hemodialysis parameters are unknown

Extracorporeal Treatment in Phenytoin Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup

The Extracorporeal Treatments in Poisoning (EXTRIP) Workgroup conducted a systematic literature review using a standardized process to develop evidence-based recommendations on the use of extracorporeal treatment (ECTR) in patients with phenytoin poisoning. The authors reviewed all articles, extracted data, summarized findings, and proposed structured voting statements following a predetermined format. A 2-round modified Delphi method was used to reach a consensus on voting statements, and the RAND/UCLA Appropriateness Method was used to quantify disagreement. 51 articles met the inclusion criteria. Only case reports, case series, and pharmacokinetic studies were identified, yielding a very low quality of evidence. Clinical data from 31 patients and toxicokinetic grading from 46 patients were abstracted. The workgroup concluded that phenytoin is moderately dialyzable (level of evidence = C) despite its high protein binding and made the following recommendations. ECTR would be reasonable in select cases of severe phenytoin poisoning (neutral recommendation, 3D). ECTR is suggested if prolonged coma is present or expected (graded 2D) and it would be reasonable if prolonged incapacitating ataxia is present or expected (graded 3D). If ECTR is used, it should be discontinued when clinical improvement is apparent (graded 1D). The preferred ECTR modality in phenytoin poisoning is intermittent hemodialysis (graded 1D), but hemoperfusion is an acceptable alternative if hemodialysis is not available (graded 1D). In summary, phenytoin appears to be amenable to extracorporeal removal. However, because of the low incidence of irreversible tissue injury or death related to phenytoin poisoning and the relatively limited effect of ECTR on phenytoin removal, the workgroup proposed the use of ECTR only in very select patients with severe phenytoin poisoning

Hemodialysis acutely improves hepatic CYP3A4 metabolic activity

The uremic syndrome remains poorly understood despite the widespread availability of dialysis for almost four decades. To date, assessment of the biologic activity of uremic toxins has focused primarily on in vitro effects, rather than on specific biochemical pathways or enzymatic activity in vivo. The activity of cytochrome P450 (CYP) 3A4, the most important enzyme in human drug metabolism, is decreased in uremia. The purpose of this study was to assess the effect of hemodialysis and hence varying concentrations of uremic toxins on CYP3A4 activity using the 14 C-erythromycin breath test and the traditional phenotypic trait measure, 20-min 14 CO 2 flux. CYP3A4 activity increased by 27% postdialysis (P ‫؍‬ 0.002 compared with predialysis) and was significantly inversely related to plasma blood urea nitrogen concentration (r s ‫؍‬ ؊0.50, P ‫؍‬ 0.012), but not to several middle molecules. This is the first study in humans characterizing uremia as a state in which hepatic CYP3A4 activity is acutely improved by hemodialysis. J Am Soc Nephrol 17: 2363 -2367 The regulation of CYP3A4 in ESRD patients undergoing hemodialysis has not been well studied. Alterations in CYP3A4 expression and/or activity have been observed in experimental models of uremia (2,3,8 to 13) and a recent report using the 14 C-erythromycin breath test demonstrates that CYP3A4 activity is reduced in ESRD patients compared to healthy subjects (14). Although restoration of kidney function after transplantation leads to a sustained improvement in the uremic state and in hepatic drug metabolism (2,15), hemodialysis therapy only temporarily improves uremia and does not appear to generate long-term improvements in CYP3A function (2). However, the acute effect of hemodialysis on CYP3A4 activity in vivo has not been studied to date. We hypothesized that hepatic CYP3A4 activity would be inversely related to the level of uremic toxins, and that removal of uremic toxins via hemodialysis would lead to acute changes in CYP3A4 activity. Thus, the purpose of this study was to assess the effect of conventional hemodialysis on hepatic CYP3A4 metabolic activity in ESRD patients using the erythromycin breath test and the phenotypic trait measure 20-min 14 CO 2 flux, and to evaluate the relationship between CYP3A4 activity and the concentrations of several uremic toxins. Materials and Methods Study Subjects Twelve patients with ESRD and undergoing chronic hemodialysis participated in this study after providing written informed consent. All subjects underwent a screening evaluation that was based on a complete medical history, physical examination, medication history, and conventional biochemical tests. Eligibility criteria included normal hepatic function, body weight within 40% of ideal weight for height, body frame size, and sex according to the 1983 Metropolitan Life Insurance Company weight tables (16), documented compliance with dialysis prescriptions as determined by a Kt/V Ն1.20 within the 28-d period before the study day, and a negative pregnancy test for women of child-bearing potential. Subjects taking drugs known to inhibit or induce CYP3A4 or with a known sensitivity or previous adverse reaction to erythromycin were excluded. All participants were instructed to abstain from grapefruit products and herbal supplements/teas for at least 72 h before and during the study day

In Vivo Alterations in Drug Metabolism and Transport Pathways in Patients with Chronic Kidney Diseases

This study was designed to prospectively evaluate the in vivo activities of drug transporters, metabolizing enzymes and pharmacokinetics in patients with chronic kidney diseases (CKD) caused by glomerulonephritis and non-glomerular etiologies

Chronic kidney disease and arrhythmias: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference.

Patients with chronic kidney disease (CKD) are predisposed to heart rhythm disorders, including atrial fibrillation (AF)/atrial flutter, supraventricular tachycardias, ventricular arrhythmias, and sudden cardiac death (SCD). While treatment options, including drug, device, and procedural therapies, are available, their use in the setting of CKD is complex and limited. Patients with CKD and end-stage kidney disease (ESKD) have historically been under-represented or excluded from randomized trials of arrhythmia treatment strategies,1 although this situation is changing.2 Cardiovascular society consensus documents have recently identified evidence gaps for treating patients with CKD and heart rhythm disorders [...

Cytogenetic abnormalities and fragile-x syndrome in Autism Spectrum Disorder

BACKGROUND: Autism is a behavioral disorder with impaired social interaction, communication, and repetitive and stereotypic behaviors. About 5–10 % of individuals with autism have 'secondary' autism in which an environmental agent, chromosome abnormality, or single gene disorder can be identified. Ninety percent have idiopathic autism and a major gene has not yet been identified. We have assessed the incidence of chromosome abnormalities and Fragile X syndrome in a population of autistic patients referred to our laboratory. METHODS: Data was analyzed from 433 patients with autistic traits tested using chromosome analysis and/or fluorescence in situ hybridization (FISH) and/or molecular testing for fragile X syndrome by Southern and PCR methods. RESULTS: The median age was 4 years. Sex ratio was 4.5 males to 1 female [354:79]. A chromosome (cs) abnormality was found in 14/421 [3.33 %] cases. The aberrations were: 4/14 [28%] supernumerary markers; 4/14 [28%] deletions; 1/14 [7%] duplication; 3/14 [21%] inversions; 2/14 [14%] translocations. FISH was performed on 23 cases for reasons other than to characterize a previously identified cytogenetic abnormality. All 23 cases were negative. Fragile-X testing by Southern blots and PCR analysis found 7/316 [2.2 %] with an abnormal result. The mutations detected were: a full mutation (fM) and abnormal methylation in 3 [43 %], mosaic mutations with partial methylation of variable clinical significance in 3 [43%] and a permutation carrier [14%]. The frequency of chromosome and fragile-X abnormalities appears to be within the range in reported surveys (cs 4.8-1.7%, FRAX 2–4%). Limitations of our retrospective study include paucity of behavioral diagnostic information, and a specific clinical criterion for testing. CONCLUSIONS: Twenty-eight percent of chromosome abnormalities detected in our study were subtle; therefore a high resolution cytogenetic study with a scrutiny of 15q11.2q13, 2q37 and Xp23.3 region should be standard practice when the indication is autism. The higher incidence of mosaic fragile-X mutations with partial methylation compared to FRAXA positive population [50% vs 15–40%] suggests that faint bands and variations in the Southern band pattern may occur in autistic patients