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- Goscinski, Gunilla, et al.
(author)
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Propensity to release endotoxin after two repeated doses of cefuroxime in an in vitro kinetic model : Higher release after the second dose
- 2007
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In: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 60:2, s. 328-333
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Journal article (peer-reviewed)abstract
- Objectives: To study endotoxin release from two strains of Escherichia coli after exposure to two repeated doses of cefuroxime in an in vitro kinetic model. Methods: Cefuroxime in concentrations simulating human pharmacokinetics was added to the bacterial solution with a repeated dose after 12 h. In another experiment, tobramycin was given concomitantly with the second dose of cefuroxime. Samples for viable counts and endotoxin analyses were drawn before the addition of antibiotics and at 2 and 4 h after each dose. Results: The propensity to release endotoxin, expressed as log10 endotoxin release (EU)/log10 killed bacteria, was higher after the second than after the first dose, 0.80 ± 0.04 and 0.65 ± 0.01, respectively, in the ATCC strain and 0.80 ± 0.04 and 0.65 ± 0.02, respectively, in the clinical strain (P < 0.001). Endotoxin was released earlier after the second dose (P < 0.001). Addition of tobramycin at the second dose reduced the endotoxin release in comparison with that of cefuroxime alone (P < 0.001). Conclusions: The propensity to liberate endotoxin is higher after the second dose of cefuroxime than after the first, resulting in a higher release of endotoxin than expected from bacterial count. The release after the second dose can be reduced by the addition of tobramycin.
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| 6. |
- Kurland, Siri, et al.
(author)
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Human plasma protein levels alter the in vitro antifungal activity of caspofungin : An explanation to the effect in critically ill?
- 2022
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In: Mycoses. - : John Wiley & Sons. - 0933-7407 .- 1439-0507. ; 65:1, s. 79-87
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Journal article (peer-reviewed)abstract
- BackgroundRecent studies have shown low caspofungin concentrations in critically ill patients. In some patients, the therapeutic target, area under the total plasma concentration curve in relation to the minimal inhibition concentration (AUCtot/MIC), seems not to be achieved and therapeutic drug monitoring (TDM) has been proposed. Caspofungin is highly protein-bound and the effect of reduced plasma protein levels on pharmacodynamics has not been investigated.ObjectivesFungal killing activity of caspofungin in vitro was investigated under varying levels of human plasma protein.MethodsTime-kill studies were performed with clinically relevant caspofungin concentrations of 1-9 mg/L on four blood isolates of C. glabrata, three susceptible and one strain with reduced susceptibility, in human plasma and plasma diluted to 50% and 25% using Ringer's acetate.ResultsEnhanced fungal killing of the three susceptible strains was observed in plasma with lower protein content (p < .001). AUCtot/MIC required for a 1 log10 CFU/ml kill at 24 h in 50% and 25% plasma was reduced with 36 + 12 and 80 + 9%, respectively. The maximum effect was seen at total caspofungin concentrations of 4–9 × MIC. For the strain with reduced susceptibility, growth was significantly decreased at lower protein levels.ConclusionsReduced human plasma protein levels increase the antifungal activity of caspofungin in vitro, most likely by increasing the free concentration. Low plasma protein levels in critically ill patients with candidemia might explain a better response to caspofungin than expected from generally accepted target attainment and should be taken into consideration when assessing TDM based on total plasma concentrations.
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| 7. |
- Kurland, Siri, et al.
(author)
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Pharmacokinetics of Caspofungin in Critically Ill Patients in Relation to Liver Dysfunction : Differential Impact of Plasma Albumin and Bilirubin Levels
- 2019
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In: Antimicrobial Agents and Chemotherapy. - : AMER SOC MICROBIOLOGY. - 0066-4804 .- 1098-6596. ; 63:6
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Journal article (peer-reviewed)abstract
- Caspofungin has a liver-dependent metabolism. Reduction of the dose is recommended based on Child-Pugh (C-P) score. In critically ill patients, drug pharmacokinetics (PK) may be altered. The aim of this study was to investigate the prevalence of abnormal liver function tests, increased C-P scores, their effects on caspofungin PK, and whether pharmacokinetic-pharmacodynamic (PK/PD) targets were attained in patients with suspected candidiasis. Intensive care unit patients receiving caspofungin were prospectively included. PK parameters were determined on days 2, 5, and 10, and their correlations to the individual liver function tests and the C-P score were analyzed. Forty-six patients were included with C-P class A (n = 5), B (n = 40), and C (n = 1). On day 5 (steady state), the median and interquartile range for area under the curve from 0 to 24 h (AUC(0-24)), clearance (CL), and central volume of distribution (V-1) were 57.8 (51.6 to 69.8) mg.h/liter, 0.88 (0.78 to 1.04) liters/h, and 11.9 (9.6 to 13.1) liters, respectively. The C-P score did not correlate with AUC(0-24) (r = 0.03; P = 0.84), CL (r = -0.07; P = 0.68), or V-1 (r = 0.19; P = 0.26), but there was a bilirubin-driven negative correlation with the elimination rate constant (r = -0.46; P = 0.004). Hypoalbuminemia correlated with low AUC(0-24) (r = 0.45; P = 0.005) and was associated with higher clearance (r = -0.31; P = 0.062) and somewhat higher V-1 (r = -0.15; P = 0.37), resulting in a negative correlation with the elimination rate constant (r = -0.34; P = 0.042). For Candida strains with minimal inhibitory concentrations of >= 0.064 mu g/ml, PK/PD targets were not attained in all patients. The caspofungin dose should not be reduced in critically ill patients in the absence of cirrhosis, and we advise against the use of the C-P score in patients with trauma- or sepsis-induced liver injury.
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| 8. |
- Lignell, Anders, et al.
(author)
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A new in-vitro kinetic model to study the pharmacodynamics of antifungal agents : inhibition of the fungicidal activity of amphotericin B against Candida albicans by voriconazole
- 2007
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In: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 13:6, s. 613-619
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Journal article (peer-reviewed)abstract
- The aim of this study was to develop and validate a new in-vitro kinetic model for the combination of two drugs with different half-lives, and to use this model for the study of the pharmacodynamic effects of amphotericin B and voriconazole, alone or in combination, against a strain of Candida albicans. Bolus doses of voriconazole and amphotericin B were administered to a starting inoculum of C. albicans. Antifungal-containing medium was eliminated and replaced by fresh medium using a peristaltic pump, with the flow-rate adjusted to obtain the desired half-life of the drug with the shorter half-life. A computer-controlled dosing pump compensated for the agent with the longer half-life. Voriconazole and amphotericin B half-lives were set to 6 and 24 h, respectively. Pharmacokinetic parameters were close to target values when both single doses and sequential doses were simulated. Voriconazole and amphotericin B administered alone demonstrated fungistatic and fungicidal activity, respectively. Simultaneous administration resulted in fungicidal activity, whereas pre-exposure of C. albicans to voriconazole, followed by amphotericin at 8 and 32 h, resulted in fungistatic activity similar to that observed with voriconazole alone. Using this model, which allowed a combination of antifungal agents with different half-lives, it was possible to demonstrate an antagonistic effect of voriconazole on the fungicidal activity of amphotericin B. The characteristics and clinical relevance of this interaction require further investigation.
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| 9. |
- Lignell, Anders, et al.
(author)
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Characterization of the inhibitory effect of voriconazole on the fungicidal activity of amphotericin B against Candida albicans in an in vitro kinetic model
- 2008
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In: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 62:1, s. 142-8
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Journal article (peer-reviewed)abstract
- OBJECTIVES: The aim of the present investigation was to study and characterize the effect of voriconazole on the fungicidal activity of amphotericin B. METHODS: Four strains of Candida albicans susceptible to voriconazole were exposed to voriconazole and amphotericin B, either alone, simultaneously or sequentially in an in vitro kinetic model. Bolus doses resulting in voriconazole and amphotericin B concentrations of 0.005-5 and 2.5 mg/L, respectively, were administered. Antifungal-containing RPMI 1640 was eliminated and replaced by a fresh medium using a peristaltic pump, with a flow rate adjusted to obtain the desired half-lives. With two drugs tested, a computer-controlled dosing pump compensated for differences in the elimination rates. Using static time-kill methodology, one C. albicans strain was exposed to 5 mg/L voriconazole for varying durations followed by 2.5 mg/L amphotericin B after three repeated washes of voriconazole. RESULTS: Voriconazole and amphotericin B treatment alone resulted in fungistatic and fungicidal activities, respectively. Simultaneous administration of voriconazole and amphotericin B resulted in fungicidal activity, whereas only fungistatic activity was observed when repeated doses of amphotericin B were administered sequentially after voriconazole at 24-96 h. The inhibition of the fungicidal activity of amphotericin B was voriconazole dose-dependent, but seemed to be recovered once the voriconazole concentration fell below the MIC. The fungicidal activity was quickly regained after the removal of voriconazole, irrespective of the duration of voriconazole pre-exposure. CONCLUSIONS: Voriconazole inhibited the fungicidal effect of sequentially administered amphotericin B in a concentration- and time-dependent manner; the clinical significance of this needs further investigation.
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| 10. |
- Lignell, Anders, 1975-
(author)
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In vitro Pharmacodynamics of Antifungal Agents in the Treatment of Candida Infections
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Pharmacodynamic studies are important for the optimal use of antimicrobial agents. Combination antifungal therapy may be one method to improve outcome in invasive Candida infections. An in vitro kinetic model to study the pharmacodynamic effects of a combination of two antifungal agents with different elimination rates was developed and the pharmacodynamics of amphotericin B (AMB), voriconazole (VRC) or the combination was evaluated. Exposure to VRC inhibited the fungicidal activity of sequential doses of AMB against VRC-susceptible strains of C. albicans. The interaction was VRC dose-dependent. AMB activity was regained once VRC was removed or it increased gradually when the concentration of VRC had fallen below the minimum inhibitory concentration (MIC). The VRC-AMB interaction, however, was also present against strains of C. albicans, C. glabrata and C. krusei despite reduced VRC susceptibility. Against these strains the interaction was not predicted by the MIC value, suggesting that mechanisms of resistance may be of importance. Until more data are available, a reasonable recommendation is probably to avoid the sequential use of VRC followed by AMB and to use the combination of VRC and AMB for the treatment of Candida infections with caution. Only the unbound fraction of a drug is generally accepted as pharmacologically active. The activity of posaconazole (POS) with a protein binding of 98-99% was tested in serum against Candida species and compared with the calculated unbound serum concentration in protein-free media. Significant differences emerged at clinically relevant POS serum concentrations of 1.0 and 0.10 mg/l compared with the serum control regimen against one strain of C. lusitaniae. In RPMI 1640 the corresponding calculated unbound concentrations resulted in no effect for the low dose regimen compared with the RPMI 1640 control regimen. Further, against seven additional Candida strains tested, the effect of POS was greater in serum than in RPMI 1640. A flux from serum protein bound to fungal lanosterol 14α-demethylase bound POS may be the explanatory mechanism.
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