Alveolar diffusion and pharmacokinetics of linezolid administered in continuous infusion to critically ill patients with ventilator-associated pneumonia.

OBJECTIVES: This study aimed to determine the steady-state serum and alveolar concentrations of linezolid administered by continuous infusion to critically ill patients with ventilator-associated pneumonia (VAP). PATIENTS AND METHODS: This was a prospective, open-label study performed in an intensive care unit and research ward in a university hospital. Twelve critically ill adult patients with VAP received 600 mg of linezolid as a loading dose followed by 1200 mg/day by continuous infusion. After 2 days of therapy, the steady-state serum and alveolar (collected by a mini-bronchoalveolar procedure) concentrations of linezolid were determined by HPLC. RESULTS: The median (IQR) serum and epithelial lining fluid (ELF) linezolid concentrations at steady state (C(ss)) were 7.1 (6.1-9.8) and 6.9 (5.8-8.6) mg/L, respectively, and the median (IQR) AUC (AUC(0-24)) values were 169 (146-235) and 164 (139-202) mg · h/L, respectively, corresponding to a median (IQR) linezolid alveolar diffusion of 97% (80%-108%). CONCLUSIONS: Our study shows that the continuous infusion of 1200 mg of linezolid daily in critically ill patients with VAP provides satisfactory pharmacokinetic results, with a linezolid alveolar diffusion of 100% and concentrations exceeding almost twice the susceptibility breakpoint for Staphylococcus aureus (4 mg/L) in both serum and ELF for 100% of the time. However, the clinical benefit of continuous infusion in comparison with standard intermittent infusion is still to be determined.

The Multidimensional Nature of Research Ethics: Letters Issued by a French Research Ethics Committee Included Similar Proportions of Ethical and Scientific Queries.

Debate is ongoing concerning the activities and functioning of Research Ethics Committees (REC), especially a possible science-or-ethics dichotomy in research ethics review. We retrospectively analyzed 145 letters issued by a French REC over 18 months. All queries were classified in three levels: qualification (definition of the problem), category (aggregation of broader topics) and finally fields (ethical, scientific, or administrative). Overall, 971 queries were identified, of which 407 (42%), 379 (39%), and 135 (14%) were deemed ethical, scientific, and administrative queries, respectively. The most frequent concern was about participants' information. The main influencing factor was the profession of the reporting readers-scientific queries were more frequently raised by a methodologist, whereas ethical queries were more frequently raised by an ethicist. These results indicate that research ethics review is a multidimensional task that should be considered a collaborative effort.

Drug selection in French university hospitals: analysis of formularies for nine competitive pharmacological classes.

AIM: To give a panorama of the selectivity and agreement of French university hospitals' drug formularies (HDF) for nine competitive classes. METHODS: All university hospitals were asked to send their HDF and selection criteria as of January 2009 for nine competitive pharmacological classes (proton pump inhibitors, serotonin antagonists, low molecular weight heparins, erythropoietins, angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, statins, α-adrenoreceptor antagonists and selective serotonin re-uptake inhibitors). Selectivity of HDF was estimated by the percentage of drug entities selected by the hospital within the pharmacological class. Agreement between hospitals was assessed with modified kappa coefficients for multi-raters. RESULTS: Twenty-one out of the 29 hospitals agreed to participate. These hospitals selected between 34% and 63% of the drug entities available for the nine classes, which represented 18 to 35 agents. Regarding the nature of chosen drug entities, the overall level of agreement was 'fair' and varied with pharmacological classes. Selection criteria were sent by only 12 hospitals. The technical component was the most important element in all hospitals. The weight of the economic component varied between 20% and 40% in the tender's grade. DISCUSSION: Large variations were seen in the number and nature of drugs selected by university hospitals which can be attributable to two successive decision-making processes (evaluation by the Drug and Therapeutics Committee followed by the purchasing process).

Quantitative analysis of erythropoietin in human plasma by tandem mass spectrometry.

The extended use of protein drugs in therapeutics has created the need for their quantification in human plasma. A methodology using the therapeutic protein itself as internal standard for quantitative analysis by multiple reaction monitoring (MRM) has been designed and applied to epoetin beta, a recombinant human erythropoietin (rhEPO). After depletion of major proteins, plasma samples were desalted and enriched in rhEPO by reversed phase liquid chromatography prior to tryptic cleavage. Differential isotopic labeling of peptides was performed by derivatization with 2-methoxy-4,5-dehydro-imidazole. A light version (four hydrogen atoms) of this reagent was used for plasma peptides. Tryptic peptides obtained from pure rhEPO were derivatized with a heavy version (four deuterium atoms) of the same reagent and used as internal standards. Two rhEPO tryptic peptides with three MRM transitions per peptide were selected for quantification. This strategy provided a quantification limit close to 50 amol of epoetin beta per microliter of plasma (equivalent to 1.7 ng/mL), i.e., well below the expected therapeutic concentrations in plasma (around 100-500 amol/µL).

Activity of linezolid in an in vitro pharmacokinetic-pharmacodynamic model using different dosages and Staphylococcus aureus and Enterococcus faecalis strains with and without a hypermutator phenotype.

The influence of antibiotic dosages and bacterial mutator phenotypes on the emergence of linezolid-resistant mutants was evaluated in an in vitro pharmacokinetic-pharmacodynamic model. A twice-daily 0.5-h infusion of a 200-, 600-, or 800-mg dose for 48 h was simulated against four strains (MIC, 2 microg/ml): Staphylococcus aureus RN4220 and its mutator derivative MutS2, Enterococcus faecalis ATCC 29212, and a mutator clinical strain of E. faecalis, Ef1497. The peak concentrations (4.38 to 4.79, 13.4 to 14.6, and 19.2 to 19.5 microg/ml) and half-lives at beta-phase (5.01 to 6.72 h) fit human plasma linezolid pharmacokinetics. Due to its bacteriostatic property, the cumulative percentages of the dosing interval during which the drug concentration exceeded the MIC (T > MIC), 66.6 and 69.1% of the dosing interval, were not significant, except for Ef1497, with an 800-mg dose and a T > MIC of 80.9%. At the standard 600-mg dosage, resistant mutants (2- to 8-fold MIC increases) were selected only with Ef1497. A lower, 200-mg dosage did not select resistant mutants of E. faecalis ATCC 29212, but a higher, 800-mg dosage against Ef1497 did not prevent their emergence. For the most resistant mutant (MIC, 16 microg/ml), characterization of 23S rRNA genes revealed the substitution A2453G in two of the four operons, which was previously described only in in vitro mutants of archaebacteria. Nevertheless, this mutant did not yield further mutants under 600- or 200-mg treatment. In conclusion, linezolid was consistently efficient against S. aureus strains. The emergence of resistant E. faecalis mutants was probably favored by the rapid decline of linezolid concentrations against a strong mutator, a phenotype less exceptional in E. faecalis than in S. aureus.

Virological and immunological response in HIV-1-infected patients with multiple treatment failures receiving raltegravir and optimized background therapy, ANRS CO3 Aquitaine Cohort.

BACKGROUND: The efficacy of raltegravir plus optimized background therapy (OBT) has been demonstrated for antiretroviral (ARV)-experienced HIV-1-infected patients in randomized clinical trials. We studied viro-immunological response, pharmacokinetic parameters and genotypic test results in an observational cohort of multiple ARV class-experienced patients starting a raltegravir-based regimen. METHODS: Already enrolled ANRS CO3 Aquitaine Cohort patients with virological failure were included in this study after starting a raltegravir-based regimen (400 mg twice a day, week 0). Virological success was defined by the plasma HIV-1 RNA level [viral load (VL)] <2.7 log(10) copies/mL at week 12 and <1.7 log(10) copies/mL at week 24. One patient was excluded from further analysis (no follow-up after week 4). RESULTS: Fifty-one patients [male/female = 43/8, median age = 48 (interquartile range = 43, 55) years] were included. At week 0, median CD4 count was 244 (110; 310)/mm(3) and median VL was 4.2 (3.6, 4.7) log(10) copies/mL. At week 24, 39 (78%) patients experienced virological success: 4 (44%), 14 (82%) and 21 (87%) patients with a genotypic sensitivity score <1, > or =1 and <2 and > or =2 (P = 0.02), respectively. Raltegravir-related mutations emerged in 9 of 11 failing patients (82%): Q148H/R (n = 5), N155S/H (n = 3) and S230N (n = 1). Median CD4 increases from week 0 to week 4 and week 24 were 28 (-4, 85) and 57 (0, 156) cells/mm(3), respectively. A poor immune response was independently associated with a lower VL decline (week 0 to week 12) [odds ratio (OR): 3.5, 95% confidence interval (CI): 1.4, 8.4, for 1 log(10) less] and CD4+% at baseline (OR: 2.6, 95% CI: 0.97, 8.3, for 10% lower). CONCLUSIONS: Raltegravir plus OBT provided a good virological success rate in highly pre-treated patients under clinical routine conditions.

Pharmacokinetics and Pharmacodynamics of Anti-infective Agents during Continuous Veno-venous Hemofiltration in Critically Ill Patients: Lessons Learned from an Ancillary Study of the IVOIRE Trial.

BACKGROUND: Hemofiltration rate, changes in blood and ultrafiltration flow, and discrepancies between the prescribed and administered doses strongly influence pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial agents during continuous veno-venous hemofiltration (CVVH) in critically ill patients. METHODS: Ancillary data were from the prospective multicenter IVOIRE (hIgh VOlume in Intensive caRE) study. High volume (HV, 70 mL/kg/h) was at random compared with standard volume (SV, 35 mL/kg/h) CVVH in septic shock patients with acute kidney injury (AKI). PK/PD parameters for all antimicrobial agents used in each patient were studied during five days. RESULTS: Antimicrobial treatment met efficacy targets for both percentage of time above the minimal inhibitory concentration and inhibitory quotient. A significant correlation was observed between the ultrafiltration flow and total systemic clearance (Spearman test: P < 0.005) and between CVVH clearance and drug elimination half-life (Spearman test: P < 0.005). All agents were easily filtered. Mean sieving coefficient ranged from 38.7% to 96.7%. Mean elimination half-life of all agents was significantly shorter during HV-CVVH (from 1.29 to 28.54 h) than during SV-CVVH (from 1.51 to 33.85 h) (P < 0.05). CONCLUSIONS: This study confirms that CVVH influences the PK/PD behavior of most antimicrobial agents. Antimicrobial elimination was directly correlated with convection rate. Current antimicrobial dose recommendations will expose patients to underdosing and increase the risk for treatment failure and development of resistance. Dose recommendations are proposed for some major antibiotic and antifungal treatments in patients receiving at least 25 mL/kg/h CVVH.

Virological response to darunavir/ritonavir-based regimens in antiretroviral-experienced patients (PREDIZISTA study).

BACKGROUND: We assessed the association of baseline HIV-1 mutations, phenotypic sensitivity and pharmacokinetics with virological failure (VF) at week 12 (W12) after onset of a darunavir/ritonavir (DRV/r)-based regimen in a cohort of 67 antiretroviral-experienced HIV-patients failing on highly active antiretroviral therapy (HAART). METHODS: VF was defined as HIV RNA >2.3 log10copies/ml at W12. HIV reverse transcriptase and protease sequencing was performed at WO; mutations with a P-value <0.25 in univariable analyses were used for a backward selection to find the best mutation set for VF prediction. Genotypic and phenotypic sensitivity scores were calculated and virtual phenotype predicted fold change (FC) assessed. DRV Cmin, Cmax, AUC(0-->12 h) and genotypic inhibitory quotient (GIQ) were determined. RESULTS: Patients had a median of 15 previous treatments for 10 years. Median W0 values included a T-cell count of 129 cells/microl, 4.7 log10 HIV RNA copies/ml, four major protease and six nucleoside reverse transcriptase inhibitor resistance mutations. At W12, median HIV RNA decrease was -2.1 log10 copies/ml with a gain of +67 CD4+ T-cells/microl; 40% of patients failed. We determined the genotypic score I13V+V32I+L33F/I/V+E35D+ M361/L/V+I47V+F53L+I62V. According to <4, 4-5 and >5 mutations, failure occurred in 11%, 48% and 100% of patients. Failure was associated with CDC stage, baseline CD4+ T-cell count, number of major protease inhibitor resistance mutations, FC and DRV/r score. Pharmacokinetics were not associated with failure, but GIQ was. CONCLUSION: At W12, 60% of heavily pretreated patients responded on DRV/r-based HAART. Genotypic and phenotypic information constituted the main virological response determinant in patients with optimal drug concentrations.

Alveolar concentrations of piperacillin/tazobactam administered in continuous infusion to patients with ventilator-associated pneumonia.

OBJECTIVES: To determine the steady-state serum and alveolar concentrations of piperacillin/tazobactam administered in continuous infusion to critically ill patients with ventilator-associated pneumonia and various degrees of renal failure. DESIGN: Prospective comparative study. SETTING: An intensive care unit and research ward in a university hospital. PATIENTS: Forty patients with microbiologically documented ventilator-associated pneumonia. INTERVENTIONS: Patients were randomized to receive piperacillin/tazobactam daily continuous infusions of 12/1.5 g or 16/2 g after a loading dose of 4/0.5 g. The serum and alveolar piperacillin/tazobactam concentrations were determined at steady-state with high performance liquid chromatography. MEASUREMENTS AND MAIN RESULTS: The median (interquartile) serum and alveolar piperacillin concentrations were respectively 25.3 mg/L (23.1-32.6) and 12.7 mg/L (6.7-18.0) for 12/1.5 g/day, and 38.9 mg/L (32.9-59.6) and 19.1 mg/L (14.0-21.5), respectively, for 16/2 g/day in patients with no/mild renal failure. In patients with moderate/advance renal failure, the median (interquartile) serum and alveolar piperacillin concentrations were 102.4 mg/L (97.4-112.6) and 44.1 mg/L (33.4-48.3), respectively, for 12/1.5 g/day, and 135.3 mg/L (119.5-146.2) and 54.9 mg/L (45.2-110.3), respectively, for 16/2 g/day. Our results show great variability in piperacillin/tazobactam concentrations, with an alveolar percentage penetration of 40-50% for piperacillin and 65-85% for tazobactam and a negative association between serum or alveolar concentrations and creatinine clearance. CONCLUSIONS: A target piperacillin serum concentration of at least 35-40 mg/L is probably required to provide alveolar concentrations exceeding the susceptibility breakpoint for gram-negative bacteria (16 mg/L) during ventilator-associated pneumonia. In patients with no/mild renal failure, a continuous daily dose of piperacillin/tazobactam 16/2 g allows reaching this target concentration, which might be not observed with 12/1.5 g/day. In patients with moderate/advanced renal failure, both dosages achieve serum concentrations far above the 35-40 mg/L threshold, suggesting that in that case, therapeutic drug monitoring should be performed in order to adjust the daily dose.

Contrasting effects of human THP-1 cell differentiation on levofloxacin and moxifloxacin intracellular accumulation and activity against Staphylococcus aureus and Listeria monocytogenes.

BACKGROUND AND AIMS: Listeria monocytogenes and Staphylococcus aureus invade and multiply in THP-1 monocytes. Fluoroquinolones accumulate in these cells, but are less active against intracellular than extracellular forms of L. monocytogenes and S. aureus. We examined whether differentiation of THP-1 monocytes into adherent, macrophage-like cells increases fluoroquinolone uptake and activity. METHODS: THP-1 monocytes were differentiated with phorbol myristate acetate (PMA) and compared with unstimulated cells for: (i) moxifloxacin and levofloxacin accumulation; and (ii) activity against phagocytosed L. monocytogenes and S. aureus (5 h contact). RESULTS: The differentiation of THP-1 monocytes caused: (i) a 3- to 4-fold increase in moxifloxacin uptake and a significant increase in its activity against intracellular L. monocytogenes (from 1.3 log(10) to 2.1 log(10) cfu decrease compared with the post-phagocytosis inoculum), but not against S. aureus (1.0-1.2 log(10) cfu decrease throughout); and (ii) no change in levofloxacin accumulation and intracellular activity against either L. monocytogenes or S. aureus. CONCLUSIONS: Although differentiation of monocytes enhances the uptake and activity of moxifloxacin against L. monocytogenes, this cannot be extended to other intracellular bacteria and to levofloxacin. These results further demonstrate that antibiotic intracellular accumulation and activity are not necessarily linked and suggest that intracellular drug and pathogen combinations must be studied individually.

Reliability of mini-bronchoalveolar lavage for the measurement of epithelial lining fluid concentrations of tobramycin in critically ill patients.

OBJECTIVE: To evaluate the reliability of mini-bronchoalveolar lavage (mini-BAL) for the measurement of tobramycin concentrations in epithelial lining fluid (ELF) in comparison with conventional bronchoscopic bronchoalveolar lavage (BAL). DESIGN: Prospective, open-label study. SETTING: An intensive care unit and research ward in a university hospital. PATIENTS: Twelve critically ill adult patients with ventilator-associated pneumonia (VAP). INTERVENTIONS: All subjects received intravenous infusions of tobramycin 7-10 mg/kg once daily. After 2 days of therapy, the steady-state serum and ELF concentrations (obtained from BAL and mini-BAL) of tobramycin were determined by means of high-performance liquid chromatography. MEASUREMENTS AND RESULTS: We observed poor penetration of tobramycin in ELF of approximately approximately 12% with ELF peak concentrations of approximately approximately 3 mg/l with both methods. Good agreement in Bland-Altman analysis (mean +/- SD bias = 0.04 +/- 0.38 mg/l) was observed between the two methods of sampling. CONCLUSION: Our results suggest that tobramycin 7-10 mg/kg once daily in critically ill patients with VAP might provide insufficient lung concentrations in the case of difficult-to-treat pathogens. Besides, mini-BAL, which is simple, non-invasive and easily repeatable at the bedside, appears to be a reliable method for the measurement of antibiotic concentrations in ELF in comparison with bronchoscopic BAL in critically ill patients with VAP.

Determination of linezolid in growth media by high-performance liquid chromatography with on-line extraction.

An isocratic high-performance liquid chromatography (HPLC) method with on-line extraction has been developed to determine linezolid in Mueller-Hinton broth. The loading mobile phase consisting of water-acetonitrile 99:1 (v/v) allowed retention of the analyte on a LiChrocart 4-4 pre-column filled with a LiChrospher 100 RP-8, 5 microm. The transfer of the analyte by a backflush mode to a 150 mm x 4.6 mm I.D. Kromasil C8 5 microm column was performed using a mobile phase of water-acetonitrile 80:20 (v/v). UV detection at 254 nm allowed a quantification limit of 0.39 microg/mL with a 50-microL sample size. The method was successfully applied to in vitro pharmacokinetic-pharmacodynamic studies.

Virological responses to atazanavir-ritonavir-based regimens: resistance-substitutions score and pharmacokinetic parameters (Reyaphar study).

OBJECTIVE: To assess the impact of baseline HIV-1 substitutions, individual pharmacokinetic (PK) parameters (Cmin, Cmax, area under the curve [AUC0-->24 h]) and genotype-inhibitory quotient (GIQ) on virological responses (VR) to atazanavir-ritonavir (300 mg/100 mg)-based highly active antiretroviral therapy (HAART) in 71 antiretroviral-experienced, atazanavir-naive patients in virological failure (VF) on HAART. METHODOLOGY: VR was defined as HIV RNA <1.7 log10 copies/ml at week 12 (W12). A clinically relevant genotype-substitutions score for atazanavir-ritonavir was developed and validated (Reyaphar substitutions score). Previously published substitutions scores were also tested. RESULTS: Patients had a median (Q1; O3) of 6 (3; 8) previous treatment lines during 9 (7; 11) years. Baseline (WO) values were as follows: 262 (187; 435) CD4+/microl, 3.9 (2.6; 4.9) log10 HIV-1 RNA copies/ml, 4 (2; 6) protease substitutions and 3 (1; 4) NRTI-related substitutions. Respective steady-state Cmin, Cmax and AUC0-->24 h were 300 (200; 700) ng/ml, 620 (430; 750) ng/ml and 78,000 (61,000; 94,000) ng.h/ml. At W12, 49% of the patients had VR with a median decrease of -1.2 (-0.5; -2.3) log10 HIV-1 RNA copies/ml. The Reyaphar score included 12 baseline protease substitutions from the International AIDS Society USA list that were associated with poorer VR: L10I/F/R/V, K20I/M/R, L241, M461/L, 154L/M/T/V, L63P, A71I/L/V/T, G73A/C/F/T, V771, V82A/F/S/T, 184V, L90M and the polymorphism substitution Q58E. Comparing <5 versus > or =5 Reyaphar substitutions, the W12-W0 HIV-1 RNA decrease was - 1.4 (-0.7; -2.3) versus -0.5 (-1.2; +0.5) log10 copies/ml (P=0.009) with VR in 63% versus 110% (P<10(-4)), respectively. This score predicted VF at W12 with 46% sensitivity, compared to 33% and 28% for the ANRS 2004 and 2005 scores. PK parameters alone were not associated with VR, but GIQ was associated with virological outcome (P=0.04). 150L, known to be correlated with atazanavir-specific resistance, emerged in 2 (8%) of the 24 failing patients with paired genotypes at WO and VF. CONCLUSIONS: These findings highlight the need to cross-validate genotype-based algorithms to interpret substitution impact on virological outcome using different patient databases before their implementation in routine clinical practice.

Pharmacokinetics and lung concentrations of ertapenem in patients with ventilator-associated pneumonia.

OBJECTIVE: We conducted a prospective, open-label study to determine the steady-state serum and epithelial lining fluid (ELF) concentrations of unbound ertapenem administered once daily to critically ill patients with early-onset ventilator-associated pneumonia (VAP). DESIGN AND SETTING: Prospective, open-label study in an intensive care unit and research ward in a university hospital. PATIENTS: Fifteen patients with VAP received 1-h intravenous infusions of 1 g ertapenem once daily. INTERVENTIONS: After 2 days of therapy the steady-state serum and ELF concentrations of free ertapenem were determined by high-performance liquid chromatography. MEASUREMENTS AND RESULTS: The median (interquartile range) free ertapenem peak (C(max)), intermediate (C(12)), and trough (C(min)) concentrations (mg/l) 1, 12, and 24 h after the end of infusion were 30.3 (27.1-37.8), 4.8 (3.9-6.4), and 0.8 (0.5-1.2) in serum and 9.4 (8.0-10.7), 2.0 (1.1-2.5), and 0.3 (0.2-0.4) in ELF, respectively, showing a median free ertapenem percentage penetration in ELF of approx. 30%. The median (interquartile range) serum area under concentration-time curve of free ertapenem during the observational period was 226.7 mg h(-1) l(-1) (202.2-263.9). CONCLUSION: Our study shows satisfactory results, with unbound ertapenem concentrations both in serum and ELF exceeding the MIC(90) values of most of the causative pathogens encountered in early-onset VAP during 50-100% time. This suggests that 1 g intravenous ertapenem administered once daily should be effective during the treatment of early-onset VAP in critically ill patients with no known risk factors for multidrug-resistant pathogens.

Determination of free ertapenem in plasma and bronchoalveolar lavage by high-performance liquid chromatography with ultraviolet detection.

A sensitive assay for the determination of unbound ertapenem in human plasma and bronchoalveolar lavage (BAL) was developed using ultrafiltration of plasma and BAL samples. A rapid HPLC method was used with ultraviolet detection set at a wavelength of 305 nm and a separation on a Prontosil AQ C18 column, with imipenem used as internal standard. This assay was linear over the concentration range of 0.5-100 microg/mL and 0.25-50 microg/mL in plasma and BAL, respectively. Limits of detection and quantitation were respectively 0.05 and 0.25 microg/mL. Validation data for accuracy and precision were CV<2.48 and 8.25%, accuracy in the range 98.1-104.2% and 102.2-108.4%, respectively, for intra and inter-day.

Protonation equilibrium and lipophilicity of moxifloxacin.

This study was performed to characterise the protonation equilibrium at the molecular level and pH-dependent lipophilicity of moxifloxacin. After determining macro- and micro-constants, distribution features of four microspecies in aqueous phase were assessed. The apparent partition coefficient versus pH profile of moxifloxacin showed a parabolic curve in n-octanol/buffer system which reached near pI. The true partition coefficient was calculated from the log P(app) and microconstants values.

Virological, intracellular and plasma pharmacological parameters predicting response to lopinavir/ritonavir (KALEPHAR study).

OBJECTIVES: To assess the impact of HIV-1 protease mutations and intracellular and plasma lopinavir minimum concentrations (Cmin) on virological success or failure on lopinavir/ritonavir-containing highly active antiretroviral therapy (HAART). DESIGN: HIV-1-infected HAART-experienced patients included in an observational study, received lopinavir/ritonavir (400/100 mg twice a day) plus two to three nucleoside reverse transcriptase inhibitors (NRTI) or one NRTI plus one non-NRTI. A viral load less than 50 copies/ml at month 6 defined virological success. METHODS: Intracellular and plasma lopinavir concentrations were determined by high-pressure liquid chromatography with mass-spectrometry detection. Reverse transcriptase and protease genes were sequenced at baseline and the time of virological failure. RESULTS: When the 38 patients started the lopinavir/ritonavir-based regimen, baseline median (25-75th percentile) values were: CD4 cell count 218 cells/microl (133-477); plasma HIV-1-RNA load 5.3 log10 copies/ml (3.8-5.1); number of lopinavir mutations four per protease gene (two to six). Univariate analysis associated virological success or failure at month 6 (21/38 patients) with the number of baseline lopinavir mutations, intracellular and plasma lopinavir Cmin, and the genotype inhibitory quotient (GIQ) at months 1 and 6. Multivariate analysis showed that the number of baseline lopinavir mutations and intracellular and plasma lopinavir Cmin were independently associated with virological success or failure. We defined the most discriminating intracellular and plasma lopinavir Cmin efficacy thresholds (8 and 4 microg/ml, respectively) and GIQ thresholds (1 and 3, respectively). CONCLUSION: The monitoring of lopinavir/rironavir-based HAART efficacy should include the number of baseline lopinavir/ritonavir mutations, intracellular and plasma lopinavir Cmin and GIQ calculation.

Virologic response to nelfinavir-based regimens: pharmacokinetics and drug resistance mutations (VIRAPHAR study).

OBJECTIVE: To assess the impact of HIV-1 protease and reverse transcriptase (RT) mutations, and pharmacokinetic parameters on virological responses to nelfinavir (NFV)-containing highly active antiretroviral therapy. DESIGN: Naive or antiretroviral-experienced HIV-1-infected subjects were included in a non-randomized, observational cohort study and received two nucleoside RT inhibitors + NFV (750 mg three times per day or 1250 mg twice per day). Virologic success was defined as a virus load < 50 copies/ml for > 6 months. METHODS: RT and protease genes were sequenced at baseline and at the time of virological failure. Plasma NFV trough concentration (Cmin), maximum concentration (Cmax), and AUC0-tau at steady-state were subjected to population pharmacokinetic analysis. RESULTS: Patients (n = 154) enrolled between November 1998 and February 2000 started a twice per day (n = 84) or three times per day (n = 70) NFV-based regimen as first- (n = 48) or second-line therapy when protease inhibitor-naive (n = 64) or -experienced (n = 42). Median follow-up duration was 16 months. Virologic failure occurred in 88 patients. No significant differences were observed between twice per day and three times per day regimens. According to multivariate analysis, NFV Cmin and Cmax, CD4 cell count, number of baseline RT + protease gene mutations, D67N, M184V, T215F/Y in RT, and M36I in protease, were independent factors that were significantly predictive of failure. At failure, L10I, D30N, M36I, V77I, N88S/D or L90M protease mutations had emerged since baseline. Pharmacokinetic parameters were similar in patients with or without emergence of these neo-mutations. The more discriminating NFV Cmin efficacy-threshold was estimated to be 1 mg/l. CONCLUSIONS: Our data confirm the association among individual pharmacokinetic parameters, genotype pattern and virological response to NFV-containing regimens.

Plasma and lung concentrations of ceftazidime administered in continuous infusion to critically ill patients with severe nosocomial pneumonia.

OBJECTIVE: To determine the steady-state plasma and epithelial lining fluid (ELF) concentrations of ceftazidime administered in continuous infusion to critically ill patients with severe nosocomial pneumonia. DESIGN: Prospective, open-label study. SETTING: An intensive care unit and research ward in a university hospital. PATIENTS: A total of 15 adult patients with severe nosocomial bacterial pneumonia on mechanical ventilation were enrolled. INTERVENTIONS: All subjects received a 30 min intravenous infusion of 2 g ceftazidime followed by a continuous infusion of 4 g over 24 h. The concentrations of ceftazidime in plasma and ELF were determined at steady-state after 2 days of therapy by high performance liquid chromatography. MEASUREMENTS AND MAIN RESULTS: The mean +/-SD steady-state plasma and ELF concentrations of 4 g ceftazidime in continuous infusion were 39.6+/-15.2 microg/mL and 8.2+/-4.8 microg/mL, respectively, showing a mean +/-SD percentage penetration of ceftazidime into ELF of 20.6+/-8.9%. CONCLUSION: The administration of 4 g ceftazidime in continuous infusion in critically ill patients with severe nosocomial pneumonia provides concentrations in excess of the minimal inhibitory concentration of many susceptible organisms over the course of therapy both in serum and ELF. However, for some pathogens such as P. aeruginosa, higher doses of ceftazidime should be administered, or another agent should be used in combination.

Steady-state plasma and intrapulmonary concentrations of piperacillin/tazobactam 4 g/0.5 g administered to critically ill patients with severe nosocomial pneumonia.

OBJECTIVE: To determine the steady-state plasma and epithelial lining fluid (ELF) concentrations of piperacillin/tazobactam (P/T) administered to critically ill patients with severe bacterial pneumonia. DESIGN: Prospective, open-label study. SETTING: An intensive care unit and research ward in a university hospital. PATIENTS: Ten adult patients with severe nosocomial bacterial pneumonia on mechanical ventilation. INTERVENTIONS: All subjects received a 30-min intravenous infusion of P/T 4 g/0.5 g every 8 h. The steady-state plasma and ELF concentrations of P/T were determined by high-performance liquid chromatography. MEASUREMENTS AND MAIN RESULTS: The mean+/-SD steady-state plasma trough, peak, and intermediate concentrations were 8.5+/-4.6 microg/ml, 55.9+/-21.6 microg/ml, and 24.0+/-13.8 microg/ml for piperacillin, and 2.1+/-1.0 microg/ml, 4.8+/-2.1 microg/ml, and 2.4+/-1.2 microg/ml for tazobactam, respectively. The mean+/-SD steady-state intermediate ELF concentrations were 13.6+/-9.4 microg/ml for piperacillin and 2.1+/-1.1 microg/ml for tazobactam, respectively, showing a mean percentage penetration of piperacillin and tazobactam into ELF of 56.8% and 91.3 %, respectively, with a P/T ratio of 6.5:1. CONCLUSION: Our results show that during the treatment of severe nosocomial pneumonia, a regimen of P/T 4 g/0.5 g every 8 h might provide insufficient concentrations into lung tissue to exceed the MIC of many causative pathogens. This suggests that higher doses of P/T should be administered in order to maximize the antibiotic concentration at the site of infection, or that a second antimicrobial agent should be used in association.