Antibiotics Removal by Continuous Venovenous Hemofiltration with a Novel Asymmetric Triacetate Membrane Hemofilter: An in vitro Study

INTRODUCTION

Continuous renal replacement therapies (CRRTs) are essential in the treatment of critically ill patients with acute kidney injury and are also discussed as a supporting sepsis therapy. CRRT can affect antibiotics plasma concentrations.

OBJECTIVE

The effect of continuous venovenous hemofiltration (CVVH) with an asymmetric triacetate (ATA) membrane hemofilter on concentrations of antibiotics with low (meropenem), medium (vancomycin), and high (daptomycin) protein binding (PB) was investigated.

METHODS

1 L human whole blood supplemented with antibiotics was recirculated and filtrated for 6 h in vitro. Clearances and sieving coefficients (SC) were determined from antibiotics concentrations measured at filter inlet, outlet, and filtrate side. Reservoir concentration data were fitted using a first-order kinetic model.

RESULTS

Meropenem and vancomycin concentrations decreased to 5-10% of the initial plasma level, while only 50% of daptomycin were removed. Clearances and SCs were (10.8 [10.8-17.4] mL/min, SC = 0.72 [0.72-1.16]) for meropenem, (13.4 [12.3-13.7] mL/min, 0.89 [0.82-0.92]) for vancomycin, and (2.1 [1.8-2.1] mL/min, 0.14 [0.12-0.14]) for daptomycin. Removal by adsorption was negligible.

CONCLUSIONS

The clearances and SCs presented are comparable with findings of other authors. Meropenem and vancomycin, which exhibit low and medium PB, respectively, were strongly removed, while considerably less daptomycin was removed because of its high PB. Our results suggest that in clinical use of the tested antibiotics during CRRT with the ATA hemofilter, the same factors have to be considered for determining the dosing strategy as with filters with other commonly applied membrane materials.

Penetration of Ertapenem Into Different Pulmonary Compartments of Patients Undergoing Lung Surgery

Ertapenem is approved for the treatment of community-acquired pneumonia (CAP), but its in vivo penetration into lung tissue (LT), epithelial lining fluid (ELF), and alveolar cells (AC) is unknown. Fifteen patients undergoing thoracotomy were treated with 1 g intravenously for perioperative prophylaxis. Bronchoalveolar lavage was performed 1, 3, and 5 hours after ertapenem infusion. Normal LT was sampled at the time of lung extraction. Blood was collected before and at different time points up to 24 hours after infusion. Mean concentrations of ertapenem in plasma, ELF, and AC were at 1.0 hour, 63.1, 4.06, 0.004 mg/L; at 3.0 hours, 39.7, 2.59, 0.003 mg/L; and at 5.0 hours, 27.2, 2.83, 0.007 mg/L. Mean (range) concentration in LT was 7.60 (2.5-19.4) mg/kg tissue 1.5 to 4.5 hours after infusion. In plasma, ertapenem exhibited a Cmax of 94.7 +/- 23.3 mg/L and an AUC(0-last) of 501.1 +/- 266.3 mg x h/L. These results, combined with the reported (MIC)90 of most CAP bacteria, support the previously observed clinical efficacy of ertapenem in the treatment of CAP.

Ertapenem in critically ill patients with early-onset ventilator-associated pneumonia: pharmacokinetics with special consideration of free-drug concentration

OBJECTIVES

Most information about pharmacokinetics of antimicrobial agents is obtained from studies in healthy volunteers. However, antibiotics are therapeutically used in infected patients with very different pharmacokinetic properties compared with healthy individuals.

PATIENTS AND METHODS

In a single-centre, prospective, open-label study, 17 adult critically ill patients with early-onset ventilator-associated pneumonia (VAP) were treated with 1 g of ertapenem infusion once a day. Blood and urine samples were collected before and at different time-points up to 24 h after medication on day 1. Concentrations of ertapenem in plasma were determined with a validated HPLC method. Free-drug concentrations were estimated using a two-class binding site equation.

RESULTS

The overall clinical success rate of the assessable cases was 66.7% (12/16). Pharmacokinetic parameters of ertapenem in our critically ill patients were clearly different when compared to those reported in the literature for healthy volunteers. The enhanced V(z) (17 vs. 8 L) and CL(TOT) (43 vs. 20 mL/min) with resulting lower C(max) (90 vs. 253 mg/L) and AUC(0-infinity) (418 vs. 817 mg x h/L) values were mainly related to hypoalbuminaemia (range 9.2-25.6 g/L) in our patient population. A population pharmacokinetic analysis using the NONMEM program indicated creatinine clearance as a significant covariate for explaining the between-subject variability of ertapenem in the patient population. Estimated free plasma concentrations of ertapenem exceeded a MIC(90) of 2 mg/L only for 6 h (25%) after infusion.

CONCLUSIONS

For an adequate dose adjustment of highly protein-bound drugs like ertapenem, knowledge of actual albumin concentrations is necessary. A shortening of the dosage interval or continuous infusion of ertapenem should be considered to ensure optimal free concentrations in critically ill patients with severe hypoalbuminaemia and normal renal function.

A new simple HPLC assay for the quantification of ertapenem in human plasma, lung tissue, and broncho-alveolar lavage fluid

Ertapenem is an important newer broad-spectrum carbapenem antibiotic covering various infections caused by common gram-positive and -negative aerobes and anaerobes. Due to its physicochemical peculiarities, pharmacokinetic data of other carbapenems are of limited value in predicting ertapenem distribution into particular compartments of the body. This raises demand for detailed pharmacokinetic studies and, as a consequence, rapid and specific ways of analysis. The HPLC assays for the quantification of ertapenem in biological matrices reported so far are based on columns of 4.6mm I.D. and involve pre-concentration by use of column-switching. However, automated column-switching technique is not standard equipment with all analytical laboratories. Furthermore, signal-to-noise ratios are likely not to be sufficient for quantification of specimens of low concentration. Therefore, a new HPLC/UV method based on narrow-bore column design using sample pre-cleaning by liquid-liquid extraction has been developed. The assay is rapid for specimen concentrations > or =1 mg/l and is easily tuned to achieve low quantification limits at high chromatographic resolution for lower concentrated samples. The method has been successfully applied to plasma, serum, lung tissue or cell homogenates, and broncho-alveolar lavage fluid with lower limits of quantification of 40 and 20 microg/l, respectively. It was also used for the pharmacokinetic monitoring of ertapenem in humans.

The extent of induction of CYP3A by St. John’s wort varies among products and is linked to hyperforin dose

OBJECTIVE

Induction of CYP3A by St. John's wort (SJW) extracts with high hyperforin (HYF) content is well described. Since SJW products vary in the amount of HYF and other main constituents, the aim of the study was to evaluate the effect on CYP3A function of SJW preparations with a range from very low to high HYF content.

METHODS

Forty-two male, healthy volunteers were randomized into six parallel SJW medication groups with varying composition especially with regard to HYF content. Midazolam plasma concentration profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication.

RESULTS

All SJW preparations tested resulted in a decrease in midazolam AUC, although the extent of the effect differed. The extract LI 160 (HYF 41 mg/day) decreased midazolam AUC0-12h by 79.4% (95% CI -88.6; -70.1), which was significantly greater than the effect by any other medication (p<0.05). SJW powder tablets 2.7 g/day (HYF 12 mg/day) resulted in a midazolam AUC0-12h decrease of 47.9% (95% CI -59.7;-36.2), while 2.7 g/day SJW powder tablets that were almost devoid of HYF (0.13 mg/day) reduced midazolam AUC0-12h by only 21.1% (95% CI -33.9; -8.3). Considering all six SJW medications tested, the extent of midazolam AUC decrease correlated significantly with increasing HYF dose (r=-0.765, p<0.001), but not with hypericin dose (r=-0.067; p=0.673).

CONCLUSION

The extent of induction of CYP3A varies among St. John's wort products and depends on hyperforin dose.

Effect of St John's wort dose and preparations on the pharmacokinetics of digoxin

BACKGROUND AND OBJECTIVE

St John's wort preparations vary in composition, main constituents, formulation, and daily dose administered. The aim of the study was to evaluate the possible pharmacokinetic interaction of marketed St John's wort formulations and doses with digoxin.

METHODS

A randomized, placebo-controlled, parallel-group study was performed in 96 healthy volunteers in 3 study parts. A 7-day loading phase with digoxin was followed by 14 days of comedication with placebo or one of 10 St John's wort products varying in dose and formulation. The pharmacokinetics of digoxin was determined before comedication and on day 14 of comedication.

RESULTS

Comedication comprised traditionally used Hypericum products; 2 g powder without hyperforin, tea, juice, oil extract, and placebo had no significant interaction with digoxin nor did hyperforin-free extract (Ze 117) or low daily doses of hyperforin-containing Hypericum powder (1 g, 0.5 g). However, comedication with the high-dose hyperforin-rich extract LI 160 resulted in a reduction of digoxin area under the curve from time 0 to 24 hours (AUC(0-24)) of -24.8% (95% confidence interval [CI], -28.3 to -21.3), a reduction in digoxin maximal plasma concentration (C(max)) of -37% (95% CI, -42 to -32), and a reduction in digoxin plasma concentration at 24 hours after previous dosing (C(trough)) of -19% (95% CI, -27 to -11). Comedication with 4 g Hypericum powder with comparable hyperforin content resulted in a reduction in digoxin AUC(0-24) of -26.6% (95% CI, -37.3 to -15.9), a reduction in digoxin C(max) of -38% (95% CI, -48 to -18), and a reduction in digoxin C(trough) of -19% (95% CI, -27 to -10). Two grams of Hypericum powder with half the hyperforin content resulted in a less prominent reduction in AUC(0-24) of -17.7% (95% CI, -21.6 to -13.7), C(max) (-21%; 95% CI, -40 to -2), and C(trough) (-13%; 95% CI, -21 to -5).

CONCLUSIONS

The interaction of St John's wort and digoxin varies within St John's wort preparations and doses and seems to be correlated with the dose, particularly of hyperforin.

Improvement in central nervous system functions during treatment of liver failure with albumin dialysis MARS--a review of clinical, biochemical, and electrophysiological data

The Molecular Adsorbent Recirculating System (MARS) is a nonbiological liver support method based on the principles of dialysis, filtration, and adsorption. It allows the safe and efficient removal of both albumin-bound and water-soluble toxic metabolites, including ammonia, aromatic amino acids, tryptophan, and related phenolic and indolic products, as well as benzodiazepines. A well-documented effect of the treatment is the improvement of the hemodynamic situation of decompensated chronic patients. Systemic vascular resistance, mean arterial pressure, cerebral blood flow, and cerebral oxygen consumption increased significantly. The degree of hepatic encephalopathy decreased significantly. Increased intracranial pressure could be normalized in both chronic and fulminant liver failure. In three randomized clinical trials significant improvement of survival could be demonstrated. In a model of murine neuronal networks cultured on multi-microelectrode array plates and incubated with plasma from liver failure patients, a normalization of the spike and burst pattern could be observed, if plasma samples from MARS-treated patients before and after treatment were compared. In conclusion, MARS significantly improves central nervous system functions. It can serve as a model for the further investigation of the role of protein-bound substances in hepatic encephalopathy and cerebral hemodynamics.

Pharmacokinetics of piperacillin-tazobactam in anuric intensive care patients during continuous venovenous hemodialysis

The pharmacokinetics of piperacillin-tazobactam were investigated in eight anuric intensive care patients treated by continuous venovenous hemodialysis (CVVHD). The elimination half-life of piperacillin was 4.3 +/- 1.2 h, and that of tazobactam was 5.6 +/- 1.3 h. The contribution of CVVHD to the overall elimination was relevant (>25%) for both drugs.

[Persistent Lactobacillus casei subspecies rhamnosus bacteremia in a 14 year old girl with acute myeloid leukemia. A case report]

The present clinical observation is related to a 14-year-old girl suffering from acute myeloid leukemia. The clinical course was complicated by episodes of severe enterocolitis, E. coli- septicemia, pancreatitis and pneumonia. In the course of continued cytostatic and antibiotic treatment a persistent asymptomatic Lactobacillus casei subsp. rhamnosus-bacteremia became detectable by a total of 18 blood cultures. Microbial cultures of the faeces revealed colony-forming unites of this germ in orders of 10(9)/g. Antibiotic eradication attempts according to the resistogram were not successful. The Lactobacillus-bacteremia disappeared only after 13 months when the cytostatic therapy was terminated. An adjuvant influence of the Lactobacillus infection on the outcome of the underlying disease cannot be excluded.