Pharmacodynamics and pharmacokinetics of a 72-hour infusion of 9-aminocamptothecin in adult cancer patients.

1997 ◽  
Vol 15 (4) ◽  
pp. 1492-1501 ◽  
Author(s):  
C H Takimoto ◽  
W Dahut ◽  
M T Marino ◽  
H Nakashima ◽  
M D Liang ◽  
...  
Keyword(s):  
Steady State ◽  
Topoisomerase I ◽  
High Performance ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Volume Of Distribution ◽  
Drug Dose ◽  
Clinical Activity ◽  
Elimination Kinetics ◽  
Dose Levels

PURPOSE To investigate the pharmacokinetics and pharmacodynamics of 9-aminocamptothecin (9-AC) infused over 72 hours at doses of 5 to 74 micrograms/m2/h. PATIENTS AND METHODS 9-AC lactone and total (lactone plus carboxylate) plasma concentrations were measured in 44 patients with solid tumors using a high-performance liquid chromatography (HPLC) assay. Fifteen patients underwent extended pharmacokinetic sampling to determine the distribution and elimination kinetics of 9-AC. RESULTS At steady-state, 8.7% +/- 4.7% (mean +/- SD) of the total drug circulated in plasma as the active 9-AC lactone. Clearance of 9-AC lactone was uniform (24.5 +/- 7.3 L/h/m2) over the entire dose range examined; however, total 9-AC clearance was nonlinear and increased at higher dose levels. In 15 patients treated at dose levels > or = 47 micrograms/m2/h, the volume of distribution at steady-state for 9-AC lactone was 195 +/- 114 L/m2 and for total 9-AC it was 23.6 +/- 10.6 L/m2. The elimination half-life was 4.47 +/- 0.53 hours for 9-AC lactone and 8.38 +/- 2.10 hours for total 9-AC. In pharmacodynamic studies, dose-limiting neutropenia correlated with steady-state lactone concentrations (Css) R2 = .77) and drug dose (R2 = .71). CONCLUSION Plasma 9-AC concentrations rapidly declined to low levels following the end of a 72-hour infusion and the mean fraction of total 9-AC circulating in plasma as the active lactone was less than 10%. The pharmacokinetics of 9-AC may have a great impact on its clinical activity and should be considered in the design of future clinical trials of this topoisomerase I inhibitor.

scholarly journals The Role of Pharmacokinetics in Anaesthesia: Application to Intravenous Infusions

1987 ◽  
Vol 15 (1) ◽  
pp. 7-14 ◽  
Author(s):  
D. R. Stanski
Keyword(s):  
Steady State ◽  
Plasma Concentration ◽  
Plasma Concentrations ◽  
Pharmacokinetic Profile ◽  
Volume Of Distribution ◽  
Drug Dose ◽  
Metabolic Clearance ◽  
Drug Infusion ◽  
Fixed Rate ◽  
Elimination Half

Pharmacokinetic concepts describe the relationship between drug dose and resulting plasma concentration. A drug's pharmacokinetic profile can be described by distribution and elimination half-lives, initial volume of distribution, steady-state distribution volume, and metabolic and distributional clearance. After initiating a fixed rate of drug infusion, four to five terminal elimination half-lives are required to reach a steady state of constant plasma concentration. If a loading dose is given, a steady state can be achieved more rapidly. The most rapid method of achieving a constant plasma concentration involves using a variable rate of drug infusion that adjusts for the metabolic clearance and distribution of the drug. Computer-driven infusion pumps can be used to rapidly achieve, then maintain, constant plasma concentrations of a drug.

scholarly journals Comparison of Plasma, Epithelial Lining Fluid, and Alveolar Macrophage Concentrations of Solithromycin (CEM-101) in Healthy Adult Subjects

2012 ◽  
Vol 56 (10) ◽  
pp. 5076-5081 ◽  
Author(s):  
Keith A. Rodvold ◽  
Mark H. Gotfried ◽  
J. Gordon Still ◽  
Kay Clark ◽  
Prabhavathi Fernandes
Keyword(s):  
Steady State ◽  
High Performance ◽  
Healthy Adult ◽  
Plasma Concentrations ◽  
Epithelial Lining ◽  
Time Curve ◽  
Epithelial Lining Fluid ◽  
Once Daily ◽  
Drug Concentrations ◽  
The Mean

ABSTRACTThe steady-state concentrations of solithromycin in plasma were compared with concomitant concentrations in epithelial lining fluid (ELF) and alveolar macrophages (AM) obtained from intrapulmonary samples during bronchoscopy and bronchoalveolar lavage (BAL) in 30 healthy adult subjects. Subjects received oral solithromycin at 400 mg once daily for five consecutive days. Bronchoscopy and BAL were carried out once in each subject at either 3, 6, 9, 12, or 24 h after the last administered dose of solithromycin. Drug concentrations in plasma, ELF, and AM were assayed by a high-performance liquid chromatography-tandem mass spectrometry method. Solithromycin was concentrated extensively in ELF (range of mean [± standard deviation] concentrations, 1.02 ± 0.83 to 7.58 ± 6.69 mg/liter) and AM (25.9 ± 20.3 to 101.7 ± 52.6 mg/liter) in comparison with simultaneous plasma concentrations (0.086 ± 0.070 to 0.730 ± 0.692 mg/liter). The values for the area under the concentration-time curve from 0 to 24 h (AUC0–24values) based on mean and median ELF concentrations were 80.3 and 63.2 mg · h/liter, respectively. The ratio of ELF to plasma concentrations based on the mean and median AUC0–24values were 10.3 and 10.0, respectively. The AUC0–24values based on mean and median concentrations in AM were 1,498 and 1,282 mg · h/L, respectively. The ratio of AM to plasma concentrations based on the mean and median AUC0–24values were 193 and 202, respectively. Once-daily oral dosing of solithromycin at 400 mg produced steady-state concentrations that were significantly (P< 0.05) higher in ELF (2.4 to 28.6 times) and AM (44 to 515 times) than simultaneous plasma concentrations throughout the 24-h period after 5 days of solithromycin administration.

8-Hydroxylation and Glucuronidation of Mirtazapine in Japanese Psychiatric Patients: Significance of the Glucuronidation Pathway of 8-Hydroxy-Mirtazapine

2019 ◽  
Vol 52 (05) ◽  
pp. 237-244
Author(s):  
Masataka Shinozaki ◽  
Jason Pierce ◽  
Yuki Hayashi ◽  
Takashi Watanabe ◽  
Taro Sasaki ◽  
...  
Keyword(s):  
Body Weight ◽  
Steady State ◽  
Plasma Levels ◽  
High Performance ◽  
Psychiatric Patients ◽  
Plasma Concentrations ◽  
Steady State Concentration ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
State Concentration

Abstract Introduction  To investigate the metabolism of mirtazapine (MIR) in Japanese psychiatric patients, we determined the plasma levels of MIR, N-desmethylmirtazapine (DMIR), 8-hydroxy-mirtazapine (8-OH-MIR), mirtazapine glucuronide (MIR-G), and 8-hydroxy-mirtazapine glucuronide (8-OH-MIR-G). Methods  Seventy-nine Japanese psychiatric patients were treated with MIR for 1–8 weeks to achieve a steady-state concentration. Plasma levels of MIR, DMIR, and 8-OH-MIR were determined using high-performance liquid chromatography. Plasma concentrations of MIR-G and 8-OH-MIR-G were determined by total MIR and total 8-OH-MIR (i. e., concentrations after hydrolysis) minus unconjugated MIR and unconjugated 8-OH-MIR, respectively. Polymerase chain reaction was used to determine CYP2D6 genotypes. Results  Plasma levels of 8-OH-MIR were lower than those of MIR and DMIR (median 1.42 nmol/L vs. 92.71 nmol/L and 44.96 nmol/L, respectively). The plasma levels (median) of MIR-G and 8-OH-MIR-G were 75.00 nmol/L and 111.60 nmol/L, giving MIR-G/MIR and 8-OH-MIR-G/8-OH-MIR ratios of 0.92 and 59.50, respectively. Multiple regression analysis revealed that smoking was correlated with the plasma MIR concentration (dose- and body weight–corrected, p=0.040) and that age (years) was significantly correlated with the plasma DMIR concentration (dose- and body weight–corrected, p=0.018). The steady-state plasma concentrations of MIR and its metabolites were unaffected by the number of CYP2D6*5 and CYP2D6*10 alleles. Discussion  The plasma concentration of 8-OH-MIR was as low as 1.42 nmol/L, whereas 8-OH-MIR-G had an approximate 59.50 times higher concentration than 8-OH-MIR, suggesting a significant role for hydroxylation of MIR and its glucuronidation in the Japanese population.

Phase I and Pharmacokinetic Study of the Camptothecin Analog DX-8951f Administered as a 30-Minute Infusion Every 3 Weeks in Patients With Advanced Cancer

2000 ◽  
Vol 18 (23) ◽  
pp. 3986-3992 ◽  
Author(s):  
Valérie Boige ◽  
Eric Raymond ◽  
Sandrine Faivre ◽  
Michel Gatineau ◽  
Kathleen Meely ◽  
...  
Keyword(s):  
Phase I ◽  
Intravenous Infusion ◽  
Topoisomerase I ◽  
High Performance ◽  
Plasma Concentrations ◽  
Maximum Tolerated Dose ◽  
Pharmacokinetic Analysis ◽  
Phase Ii Studies ◽  
Heavily Pretreated ◽  
Dose Limiting Toxicity

PURPOSE: DX-8951f is a totally synthetic derivative of camptothecin with greater cytotoxicity and more potent topoisomerase I inhibition than SN-38, topotecan, and camptothecin in preclinical studies. This phase I study aimed to describe the toxicity and to determine the maximum-tolerated dose (MTD) and pharmacokinetics of DX-8951f given as a 30-minute intravenous infusion every 3 weeks. PATIENTS AND METHODS: Twelve patients with refractory solid malignancies were treated with DX-8951f at dose levels ranging from 4 to 7.1 mg/m2. All but one patient had received previous chemotherapy, and eight patients were considered heavily pretreated. Total DX-8951f plasma concentrations were assayed using high-performance liquid chromatography. RESULTS: Thirty-six cycles of DX-8951f were administered. Neutropenia was the dose-limiting toxicity, and it was dose-related, reversible, and noncumulative. Other toxicities included nausea and vomiting, alopecia, asthenia, fever, and anemia. Grade 1 or 2 diarrhea was observed in seven patients but was transient and resolved without requiring treatment. Pharmacokinetic analysis showed that DX-8951f had a half-life of 7.15 hours and a clearance rate of 1.65 L/h·m2. The DX-8951f area under the plasma-concentration curve increased linearly with the dose. We defined the MTD of DX-8951f administered as a 30-minute intravenous infusion every 3 weeks as 7.1 mg/m2. CONCLUSION: The dose-limiting toxicity of DX-8951f is neutropenia. The recommended dose for phase II studies is 5.33 mg/m2 every 3 weeks in patients previously treated with chemotherapy.

scholarly journals Influence of Cytochrome P450 2C19 on the pharmacokinetics of lansoprazole administered by single and successive intravenous infusion in healthy Chinese volunteers

2012 ◽  
Vol 2 (1) ◽  
pp. 3 ◽  
Author(s):  
Yongqing Wang ◽  
Peipei Zhang ◽  
Ningling Jiang ◽  
Xiaojian Gong ◽  
Dewang Wang ◽  
...  
Keyword(s):  
Intravenous Infusion ◽  
High Performance ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Linear Increase ◽  
Cytochrome P450 2C19 ◽  
Repeated Doses ◽  
Healthy Chinese ◽  
To Receive ◽  
Single Intravenous Infusion

This study aimed to explore the effect of CYP2C19 polymorphisms on the pharmacokinetics of lansoprazole administered by single and successive intravenous (iv) infusions in healthy Chinese volunteers. A total of 30 subjects, including 20 extensive metabolizers (EMs) and 10 poor metabolizers (PMs) were recruited and randomly assigned to three groups receiving doses of 15, 30 and 60 mg. All subjects received a single dose of lansoprazole during a 60-min period, and only the 30 mg dose group continued to receive the same dose iv for the next seven days (twice daily). Plasma concentrations of lansoprazole were monitored by high performance liquid chromatography (HPLC) at the following times: 15, 30, 45, 60, 75, 105, 165, 225, 300, 390, 480, 600 and 720 min after lansoprazole administration. After a single intravenous infusion in the three groups, AUC, Cmax and t½ were significantly higher in PMs than in EMs, while total clearance (Cltotal) in PMs was significantly lower than that in EMs. Mean AUC and Cmax ratios in EMs and PMs were 2.1:1 and 1.4:1, respectively. After repeated doses of 30 mg, the AUC, Cmax, and t½ increased significantly, while the Cltotal decreased significantly in EMs. Mean AUC and Cmax ratios in EMs and PMs amounted to 2.2:1.4 and 1.5:1.2, respectively. Lansoprazole displays a linear increase in AUC and Cmax over a dose range of 15-60 mg, and these were dependent on individual CYP2C19 status.

scholarly journals Analgesic and Nonanalgesic Effects of Intravenous Hydromorphone - Relation to Plasma Concentrations in Healthy Volunteers

1996 ◽  
Vol 1 (2) ◽  
pp. 86-92 ◽  
Author(s):  
D Westerling ◽  
H Bjork ◽  
P Svedman ◽  
P Hoglund
Keyword(s):  
Healthy Volunteers ◽  
Analgesic Effect ◽  
High Performance ◽  
Plasma Concentrations ◽  
Volume Of Distribution ◽  
Systemic Clearance ◽  
The Third ◽  
Elimination Half ◽  
Pressure Pain Thresholds ◽  
Saliva Production

OBJECTIVE:To investigate the analgesic and nonanalgesic effects and the pharmacokinetics of an intravenous infusion of 2 mg hydromorphone over 20 mins.DESIGN:Open study.SUBJECTS:Twelve healthy volunteers.MEASUREMENTS:The analgesic effect of hydromorphone was evaluated serially using pressure pain thresholds (PPTs) measured on the third fingers and toes. The nonanalgesic effects of hydromorphone were measured as miosis, decrease of saliva production and central nervous effects such as euphoria/dysphoria, nausea, headache, fatigue and feeling of heaviness. Plasma concentration of hydromorphone was measured using high performance liquid chromatography.RESULTS:PPTs were significantly increased compared with baseline levels for up to 2 h after the infusion of hydromorphone. Significant miosis and reduction of saliva production were registered up to 6 h after drug administration. Fatigue and heaviness were reported by all subjects. In the studied opioid-naive subjects, the hydromorphone-induced analgesic effect was of shorter duration than the studied nonanalgesic effects. The terminal elimination half-life of hydromorphone was 1.87±0.4 h (± SD) (95% CI 1.61 to 2.13), systemic clearance was 1.81±0.25 L/min (95% CI 1.65 to 1.97) and volume of distribution was 4.15±0.86 L/kg (95% CI 3.6 to 4.71).CONCLUSION:Analgesia and nonanalgesic effects appear to be well correlated with the plasma concentrations of the hydromorphone.

Phase I Trial of Fenretinide (4-HPR) Intravenous Emulsion for Hematologic Malignancies.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2581-2581 ◽  
Author(s):  
Ann Mohrbacher ◽  
Martin Gutierrez ◽  
Anthony J. Murgo ◽  
Shivaani Kummar ◽  
C. Patrick Reynolds ◽  
...  
Keyword(s):  
T Cell ◽  
Dose Level ◽  
High Performance ◽  
Dose Range ◽  
Systemic Exposure ◽  
Complete Response ◽  
Hematologic Malignancies ◽  
Clinical Activity ◽  
T Cell Lymphomas ◽  
Oral Capsule

Abstract Background: 4-HPR is a cytotoxic retinoid with broad anti-cancer activity in preclinical studies, but oral capsule 4-HPR had limited bioavailability and activity in clinical trials. An intravenous intralipid emulsion formulation of 4-HPR (ILE 4-HPR) was developed to increase 4-HPR systemic exposure. Methods: ILE 4-HPR was administered as a continuous intravenous infusion for 5 of every 21 days and systemic toxicities, clinical response, and pharmacokinetics (PK) assessed. Simon design dose escalation proceeded with a 100% increase per dose level until moderate toxicity in 2 patients or 1 dose-limiting toxicity (DLT). Ten dose levels were planned starting at 80 mg/m2/day, increasing until 1810 mg/m2. Plasma 4-HPR levels were measured by high performance liquid chromatography. Results: To date, 17 patients have been enrolled. At dose level 10 (1810 mg/m2/day), 2 patients experienced a DLT of grade 4 hypertriglyceridemia, 1 patient with transient grade 2 pancreatitis. A de-escalation to dose level 9 (1280 mg/m2/day) enrolled 5 patients: 1 had asymptomatic Grade 4 hypertriglyceridemia, 1 patient experienced pleural effusions that resolved after pleurocentesis. A de-escalation to dose level 8 (905 mg/m2/day) enrolled 5 pts: two patients experienced asymptomatic Grade 4 hypertriglyceridemias that resolved after stopping the infusion; enrollment is ongoing. PK showed a linear relationship of dose to plasma level, with steady-state 4-HPR levels of 25 μM (640 mg/m2, level 7); 54 μM (1280 mg/m2, level 9) and 62 μM (1810 mg/m2, level 10). Responses to date include a transient response in a non-Hodgkins lymphoma at 320 mg/m2, in two angioimmunoblastic T-cell lymphomas, an 8-month partial response at 1810 mg/m2/day and a 4+ month unconfirmed complete response at 905 mg/m2/day, and in a histone deacetylase inhibitor-refractory cutaneous T cell lymphoma, a 10+ month molecular complete response at 1280 mg/m2. All patients were heavily pretreated. The DLT of hypertriglyceridemia is likely related to the intralipid formulation vehicle accounting for 5/6 DLTs observed, all reversible. Conclusions: ILE 4-HPR can be safely administered and obtained 4-HPR plasma levels 6 to 7 times higher than previously obtained by oral capsule 4-HPR. Durable clinical activity was observed in T cell lymphomas in the dose range 905–1810 mg/m2. Supported in part by NCI U01CA62505 and the NCI RAID program.

A phase I study of MK-2206, an oral potent allosteric Akt inhibitor (Akti), in patients (pts) with advanced solid tumor (ST)

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 3503-3503 ◽  
Author(s):  
A. W. Tolcher ◽  
T. A. Yap ◽  
I. Fearen ◽  
A. Taylor ◽  
C. Carpenter ◽  
...  
Keyword(s):  
Dose Escalation ◽  
Whole Blood ◽  
Plasma Concentrations ◽  
Ca 125 ◽  
Clinical Activity ◽  
Akt Inhibitor ◽  
Eligibility Criteria ◽  
Phosphorylated Akt ◽  
Tumor Biopsies ◽  
Dose Levels

3503 Background: Akt facilitates cell proliferation/survival and is a suspected driver of progression in ST. MK-2206, a highly selective non-ATP competitive allosteric Akti, has nM IC50 and broad preclinical antitumor activity. Methods: Safety and tolerability of MK-2206 administered QOD in 28-day cycles (cy) was assessed. Doses evaluated: 30, 60, 90 mg, and 75 mg. Main eligibility criteria: ≥18 yo, evaluable advanced ST, ECOG ≤1, HbA1c ≤8% or fasting glucose ≤110% upper limit of normal. PK and phosphorylated Akt (pAkt) in whole blood by meso-scale ELISA were measured. Sequential tumor biopsies were performed in a subset of pts. Results: Dose escalation occurred in 19 pts (8 female/11 male; median age 57 yo; ECOG 0/1: 5/14) and 37 cy of therapy with no DLTs at 30 and 60 mg. CTCAE G3/4 skin rash and CTCAE G3 mucositis were observed at 90 mg in 4/7 pts. After further accrual at 60 mg confirmed safety at this dose, 75 mg was explored; however, 2/3 pts experienced DLT of rash. Dose escalation is complete; the MTD of MK-2206 is 60 mg QOD. Common drug-related AEs included skin (47.1%), gastrointestinal (41.2%), and general disorders (29.4%). AUC0–48hr and Cmax were dose proportional up to 60 mg. Median Tmax is 6 hrs and mean t1/2 ranged from 63 to 76 hr. MK-2206 concentrations exceeding a preliminary, statistically determined PK target of approximately 50–65 nM for significant pAkti in blood were maintained over the entire dosing interval in all patients in the 60 mg cohort. Evidence of PD activity included decreases in whole blood pAkt at all dose levels, reversible CTCAE G1/2 hyperglycemia and CTCAE G1 insulin c-peptide elevations. RECIST stable disease following 2 cycles of therapy was observed in 1 pt at 30 mg and 5 pts at 60 mg. Observed clinical activity included: central tumor necrosis, decreased ascites and peripheral edema, reduction in index lesions, normalization of LFTs, and decreased CA-125. Conclusions: MK-2206 is generally well tolerated at doses up to 60 mg QOD with plasma concentrations that portend activity in preclinical models. PK/PD data suggest a substantial and maintained target inhibition at 60 mg. [Table: see text]

Pharmacokinetics of Prilocaine after Intravenous Administration in Volunteers 

1999 ◽  
Vol 90 (4) ◽  
pp. 988-992 ◽  
Author(s):  
Auke Dirk van der Meer ◽  
Anton G. L. Burm ◽  
Rudolf Stienstra ◽  
Jack W. van Kleef ◽  
Arie A. Vletter ◽  
...  
Keyword(s):  
Intravenous Administration ◽  
High Performance ◽  
Equilibrium Dialysis ◽  
Plasma Concentrations ◽  
Volume Of Distribution ◽  
Metabolic Clearance ◽  
Unbound Fraction ◽  
Blood Samples ◽  
The Mean ◽  
The Difference

Background Prilocaine exists in two stereoisomeric configurations, the enantiomers S(+)- and R(-)-prilocaine. The drug is clinically used as the racemate. This study examined the pharmacokinetics of the enantiomers after intravenous administration of the racemate. Methods Ten healthy male volunteers received 200 mg racemic prilocaine as a 10-min intravenous infusion. Blood samples were collected for 8 h after the start of the infusion. Plasma concentrations were measured by stereoselective high-performance liquid chromatography (HPLC). Unbound fractions of the enantiomers in blank blood samples, spiked with racemic prilocaine, were determined using equilibrium dialysis. Results The unbound fraction of R(-)-prilocaine (mean +/- SD, 70%+/-8%) was smaller (P &lt; 0.05) than that of S(+)-prilocaine (73%+/-5%). The total plasma clearance of R(-)-prilocaine (2.57+/-0.46 l/min) was larger (P &lt; 0.0001) than that of S(+)-prilocaine (1.91+/-0.30 l/min). The steady-state volume of distribution of R(-)-prilocaine (279+/-94 l) did not differ from that of S(+)-prilocaine (291+/-93 l). The terminal half-life of R(-)-prilocaine (87+/-27 min) was shorter (P &lt; 0.05) than that of S(+)-prilocaine (124+/-64 min), as was the mean residence time of R(-)-prilocaine (108+/-30 min) compared with S(+)-prilocaine (155+/-59 min; P &lt; 0.005). Conclusions The pharmacokinetics of prilocaine are enantioselective. The difference in clearance is most likely a result of a difference in intrinsic metabolic clearance. The difference in the pharmacokinetics of the enantiomers of prilocaine does not seem to be clinically relevant.

scholarly journals Model Based Identification of Linezolid Exposure–toxicity Thresholds in Hospitalized Patients

2021 ◽  
Vol 12 ◽  
Author(s):  
Jie Fang ◽  
Xiao-Shan Zhang ◽  
Chun-Hong Zhang ◽  
Zi-Ye Zhou ◽  
Lu Han ◽  
...  
Keyword(s):  
Steady State ◽  
Serum Albumin ◽  
White Cell Count ◽  
Plasma Concentrations ◽  
Regression Tree ◽  
Predictive Performance ◽  
Volume Of Distribution ◽  
Classification And Regression Tree ◽  
Therapeutic Drug ◽  
Population Pharmacokinetic

Evidence supports linezolid therapeutic drug monitoring as the exposure–response relationship has been identified for toxicity among patients receiving linezolid, but the data to establish the upper limit are limited and the published toxicity thresholds range widely. The purpose of this study was to determine the linezolid exposure–toxicity thresholds to improve the safety of linezolid. This is a multicenter retrospective study of adult patients treated with linezolid from 2018 to 2019. The population pharmacokinetic model of linezolid was established based on 270 plasma concentrations in 152 patients, which showed creatinine clearance and white cell count are covariates affecting the clearance of linezolid, and serum albumin is the covariate affecting the volume of distribution. Classification and regression tree analysis was used to determine the linezolid exposure thresholds associated with an increased probability of toxicity. Among 141 patients included for toxicity analysis, the rate of occurring toxicity was significantly higher among patients with an AUC0-24, d1 ≥163 mg h/L, AUC0-24, d2 ≥207 mg h/L, AUC0-24, ss ≥210 mg h/L, and Cmin,d2 ≥6.9 mg/L, Cmin,ss ≥6.9 mg/L, while no threshold was discovered for Cmin, d1. Those exposure thresholds and duration of linezolid treatment were independently associated with linezolid-related toxicity in the logistic regression analyses. In addition, the predictive performance of the AUC0-24 and Cmin thresholds at day 2 and steady state were close. Considering that the AUC estimation is cumbersome, Cmin threshold at 48 h and steady state with a value of ≥6.9 mg/L is recommended to improve safety, especially for patients with renal insufficiency and patients with low serum albumin.

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