Cyclosporine and vancomycin disposition during continuous venovenous hemodiafiltration

Structure and Antibacterial Activity of Ambobactin, a New Telomycin-Like Cyclic Depsipeptide Antibiotic Produced by Streptomyces ambofaciens F3

A new telomycin-like cyclic depsipeptide, ambobactin (1), was isolated from the metabolites of Streptomyces ambofaciens F3, an endophyte of Platycladus orientalis. Its structure was elucidated on the basis of extensive spectroscopic analysis and advanced Marfey’s method. Ambobactin is structurally related with telomycin, except that the configuration of the 3-methyltryptophanes in their structures is different. It exhibited strong antibacterial activity against both Gram-positive and Gram-negative bacteria. Furthermore, this investigation revealed that S. ambofaciens F3 is a new producer of telomycin-like antibiotics.

Presence and accuracy of drug dosage recommendations for continuous renal replacement therapy in tertiary drug information references

BACKGROUND

Clinicians commonly rely on tertiary drug information references to guide drug dosages for patients who are receiving continuous renal replacement therapy (CRRT). It is unknown whether the dosage recommendations in these frequently used references reflect the most current evidence.

OBJECTIVE

To determine the presence and accuracy of drug dosage recommendations for patients undergoing CRRT in 4 drug information references.

METHODS

Medications commonly prescribed during CRRT were identified from an institutional medication inventory database, and evidence-based dosage recommendations for this setting were developed from the primary and secondary literature. The American Hospital Formulary System-Drug Information (AHFS-DI), Micromedex 2.0 (specifically the DRUGDEX and Martindale databases), and the 5th edition of Drug Prescribing in Renal Failure (DPRF5) were assessed for the presence of drug dosage recommendations in the CRRT setting. The dosage recommendations in these tertiary references were compared with the recommendations derived from the primary and secondary literature to determine concordance.

RESULTS

Evidence-based drug dosage recommendations were developed for 33 medications administered in patients undergoing CRRT. The AHFS-DI provided no dosage recommendations specific to CRRT, whereas the DPRF5 provided recommendations for 27 (82%) of the medications and the Micromedex 2.0 application for 20 (61%) (13 [39%] in the DRUGDEX database and 16 [48%] in the Martindale database, with 9 medications covered by both). The dosage recommendations were in concordance with evidence-based recommendations for 12 (92%) of the 13 medications in the DRUGDEX database, 26 (96%) of the 27 in the DPRF5, and all 16 (100%) of those in the Martindale database.

CONCLUSIONS

One prominent tertiary drug information resource provided no drug dosage recommendations for patients undergoing CRRT. However, 2 of the databases in an Internet-based medical information application and the latest edition of a renal specialty drug information resource provided recommendations for a majority of the medications investigated. Most dosage recommendations were similar to those derived from the primary and secondary literature. The most recent edition of the DPRF is the preferred source of information when prescribing dosage regimens for patients receiving CRRT.

The hemophagocytic syndrome: titrating continuous hemofiltration to the degree of lactic acidosis

In 3 cases of severe multiple organ failure due to hemophagocytic lymphohistiocytosis (HLH) in children, the authors demonstrate the utility of continuous hemofiltration in attenuating the consequences of excess cytokine activity, with therapy titrated to the degree of lactic acidosis. HLH was diagnosed in 3 encephalopathic children with multiple organ failure, elevated ferritin (49,396-237,582 pmol/L; or 21,983-105,733 ng/mL), elevated serum triglyceride, and depressed cell lines. One had a known malignancy, one had EBV-associated lymphoproliferative disease, and one was previously healthy. Continuous hemofiltration was initiated, with the ultrafiltrate production rate and countercurrent dialysate flow titrated to metabolic acidosis as reflected by the serum lactate (maximum 3.5 mmol/L or 31.6 mg/dL). Hemofiltration was titrated upward until lactic acidosis resolved, through clearance of lactate or interruption of excess cytokine-driven activity; maximum prescription was 2000 mL/h ultrafiltrate production plus 2500 mL/h dialysate flow. Stability was achieved with hemofiltration, then substantial resolution occurred with treatment according to the HLH-94 protocol (dexamethasone, cyclosporin, VP-16, intrathecal methotrexate). One child succumbed to candidiasis. Another made a full recovery. A third succumbed to his primary malignancy. HLH should be suspected in unexplained or unresolving multiple organ failure. Titration of hemofiltration based on measurable parameters of cellular metabolism (e.g., lactate, base deficit) may stabilize the child with metabolic acidosis long enough to allow proper diagnosis and institution of definitive therapy. Hemofiltration is not a panacea but rather a stabilizing mechanism, with poorly understood effects on interstitial water and solute flux, that facilitates recovery over weeks, not days.

Falsely elevated serum vancomycin concentrations in hemodialysis patients

Fluorescence polarization immunoassay (FPIA) is the most widely used clinical vancomycin assay in the United States. Questions exist regarding the accuracy of this polyclonal assay in patients with end-stage renal disease (ESRD). While several studies have reported discrepancies in vancomycin serum concentrations determined by FPIA compared with other vancomycin assays, no study has investigated the accuracy of vancomycin serum concentrations determined by FPIA in patients with ESRD undergoing maintenance hemodialysis. Therefore, we compared the assay performance of FPIA and enzyme multiplied immunoassay technique (EMIT) in six subjects with ESRD receiving high-efficiency hemodialysis. Subjects underwent 6 consecutive weeks of hemodialysis treatment with a cellulose acetate dialyzer (CA210) and received 1 g vancomycin intravenously once weekly during the last hour of dialysis. Vancomycin serum concentrations were determined by both EMIT and FPIA methodologies. From the serum concentration results of both assays, vancomycin dosing recommendations were calculated to achieve a desired steady-state peak concentration of 35 mg/L and trough concentration of 10 mg/L. Overall, vancomycin serum concentrations reported by FPIA were significantly higher than those reported by EMIT. The mean difference between assays in the peak serum concentrations at weeks 1, 4, and 6 was 7.5, 11.5, and 11.2 mg/L, respectively. The mean difference in trough serum concentrations at weeks 1, 4, and 6 was 4.2, 6.2, and 5.2 mg/L, respectively. The FPIA overestimation of the EMIT values (calculated as FPIA-EMIT) varied widely among study subjects with a range of 0.0 mg/L to 27.0 mg/L for peak serum concentrations and 0.0 mg/L to 12.8 mg/L for trough serum concentrations. The mean doses calculated based on FPIA results were significantly lower than the EMIT-derived doses. No significant difference was observed in the calculated dosing intervals. These results demonstrate that FPIA significantly overestimates vancomycin serum concentrations compared with EMIT in patients with ESRD undergoing high-efficiency hemodialysis. The overestimation by FPIA may result in significantly different vancomycin dosing recommendations, leading to underdosing and the potential for therapeutic failures. Due to the unpredictability of the overestimation by FPIA, we were unable to formulate vancomycin dosing guidelines for institutions that use FPIA. Therefore, we recommend that the EMIT vancomycin assay be used in patients with ESRD to ensure appropriate dosing.