Population pharmacokinetics/pharmacodynamics of micafungin against Candida species in obese, critically ill, and morbidly obese critically ill patients

Background

Dosing in obese critically ill patients is challenging due to pathophysiological changes derived from obesity and/or critical illness, and it remains fully unexplored. This study estimated the micafungin probability of reaching adequate 24-h area under the curve (AUC_0–24h)/minimum inhibitory concentration (MIC) values against Candida spp. for an obese/nonobese, critically ill/noncritically ill, large population.

Methods

Blood samples for pharmacokinetic analyses were collected from 10 critically ill nonobese patients, 10 noncritically ill obese patients, and 11 critically ill morbidly obese patients under empirical/directed micafungin treatment. Patients received once daily 100–150 mg micafungin at the discretion of the treating physician following the prescribing information and hospital guidelines. Total micafungin concentrations were determined by high-performance liquid chromatography (HPLC). Monte-Carlo simulations were performed and the probability of target attainment (PTA) was calculated using the AUC_0–24/MIC cut-offs 285 (C. parapsilosis), 3000 (all Candida spp.), and 5000 (nonparapsilosis Candida spp.). Intravenous once-daily 100-mg, 150-mg, and 200-mg doses were simulated at different body weights (45, 80, 115, 150, and 185 kg) and age (30, 50, 70 and 90 years old). PTAs ≥ 90% were considered optimal. Fractional target attainment (FTA) was calculated using published MIC distributions. A dosing regimen was considered successful if the FTA was ≥ 90%.

Results

Overall, 100 mg of micafungin was once-daily administered for nonobese and obese patients with body mass index (BMI) ≤ 45 kg/m² and 150 mg for morbidly obese patients with BMI > 45 kg/m² (except two noncritically ill obese patients with BMI ~ 35 kg/m² receiving 150 mg, and one critically ill patient with BMI > 45 kg/m² receiving 100 mg). Micafungin concentrations in plasma were best described using a two-compartment model. Weight and age (but not severity score) were significant covariates and improved the model. FTAs > 90% were obtained against C. albicans with the 200 mg/24 h dose for all body weights (up to 185 kg), and with the 150 mg/24 h for body weights < 115 kg, and against C. glabrata with the 200 mg/24 h dose for body weights < 115 kg.

Conclusion

The lack of adequacy for the 100 mg/24 h dose suggested the need to increase the dose to 150 mg/24 h for C. albicans infections. Further pharmacokinetic/pharmacodynamic studies should address optimization of micafungin dosing for nonalbicans Candida infections.

A practice-based observational study on the use of micafungin in Surgical Critical Care Units

INTRODUCTION

Echinocandins are first-line therapy in critically ill patients with invasive Candida infection (ICI). This study describes our experience with micafungin at Surgical Critical Care Units (SCCUs).

METHODS

A multicenter, observational, retrospective study was performed (12 SCCUs) by reviewing all adult patients receiving 100 mg/24h micafungin for ≥72h during ad-mission (April 2011-July 2013). Patients were divided by ICI category (possible, probable + proven), 24h-SOFA (<7, ≥7) and outcome.

RESULTS

72 patients were included (29 possible, 13 probable, 30 proven ICI). Forty patients (55.6%) presented SOFA ≥7. Up to 78.0% patients were admitted after urgent surgery (64.3% with SOFA <7 vs. 90.3% with SOFA ≥7, p=0.016), and 84.7% presented septic shock. In 66.7% the site of infection was intraabdominal. Forty-nine isolates were recovered (51.0% C. albicans). Treatment was empirical (59.7%), microbiologically directed (19.4%), rescue therapy (15.3%), or anticipated therapy and prophylaxis (2.8% each). Empirical treatment was more frequent (p<0.001) in possible versus probable + proven ICI (86.2% vs. 41.9%). Treatment (median) was longer (p=0.002) in probable + proven versus possible ICI (13.0 vs. 8.0 days). Favorable response was 86.1%, without differences by group. Age, blood Candida isolation, rescue therapy, final MELD value and %MELD variation were significantly higher in patients with non-favorable response. In the multivariate analysis (R2=0.246, p<0.001) non-favorable response was associated with positive %MELD variations (OR=15.445, 95%CI= 2.529-94.308, p=0.003) and blood Candida isolation (OR=11.409, 95%CI=1.843-70.634, p=0.009).

CONCLUSION

High favorable response was obtained, with blood Candida isolation associated with non-favorable response, in this series with high percentage of patients with intraabdominal ICI, septic shock and microbiological criteria for ICI.

A practice-based observational study identifying factors associated with the use of high-dose tigecycline in the treatment of secondary peritonitis in severely ill patients

INTRODUCTION

Based on tigecycline linear pharmacokinetic/pharmacodynamics, dose increases have been advocated to maximise activity especially when severe infections with high bacterial load and/or multidrug resistance are suspected. This practice-based observational study explored factors associated with tigecycline administration (100 mg/12h, 200 mg loading dose) in severely ill patients with complicated intra-abdominal infection (cIAI) admitted to four Surgical Critical Care Units (SCCUs).

METHODS

Medical records of all consecutive adult patients with cIAI and controlled infection source requiring surgery and admission for ≥ 48 h to SCCU were reviewed and divided into patients treated with a regimen including tigecycline (tigecycline group) and those that not (control group). A logistic regression model was performed using "tigecycline administration" (dependent variable) and variables showing differences (p ≤ 0.1) in bivariate analyses (independent variables).

RESULTS

One hundred and twenty one patients were included. In the tigecycline group, higher percentage of patients (vs. controls) presented colon as surgical site (66.7% vs. 41.8%, p = 0.006), nosocomial infection (55.6% vs. 26.9%, p = 0.001), mechanical ventilation (48.1% vs. 28.4%, p = 0.025), chronic renal replacement therapy (40.7% vs. 19.4%, p =0.008), septic shock (72.2% vs. 46.3%, p = 0.004), and higher values of SAPS II (48.0 ± 15.0 vs. 39.6 ± 15.5, p = 0.003), SOFA at admission (7.0 ± 3.3 vs. 5.5 ± 3.7, p = 0.020), lactate-24h (2.5 ± 2.8 vs. 1.6 ± 0.9, p = 0.029) and CRP-72 h (207.4 ± 87.9 vs. 163.7 ± 76.8, p = 0.021). In the multivariate analysis (R2 = 0.187, p < 0.001) nosocomial infection (OR = 7.721; 95%CI = 2.193, 27.179; p = 0.001), colon as infection site (OR = 4.338; 95%CI = 1.432, 13.145; p = 0.009) and CRP-72 h (OR = 1.009 per-unit; 95%CI = 1.002, 1.016; p = 0.012) were associated with tigecycline administration.

CONCLUSIONS

In severely ill patients with cIAI, high-dose tigecycline administration was associated with nosocomial origin of cIAI and colon as source infection site.