Dosing nomograms for attaining optimum concentrations of meropenem by continuous infusion in critically ill patients with severe gram-negative infections: a pharmacokinetics/pharmacodynamics-based approach.

The worrisome increase in Gram-negative bacteria with borderline susceptibility to carbapenems and of carbapenemase-producing Enterobacteriaceae has significantly undermined their efficacy. Continuous infusion may be the best way to maximize the time-dependent activity of meropenem. The aim of this study was to create dosing nomograms in relation to different creatinine clearance (CL(Cr)) estimates for use in daily clinical practice to target the steady-state concentrations (C(ss)s) of meropenem during continuous infusion at 8 to 16 mg/liter (after the administration of an initial loading dose of 1 to 2 g over 30 min). The correlation between meropenem clearance (CL(m)) and CL(Cr) was retrospectively assessed in a cohort of critically ill patients (group 1, n = 67) to create a formula for dosage calculation to target C(ss). The performance of this formula was validated in a similar cohort (group 2, n = 56) by comparison of the observed and the predicted C(ss)s. A significant relationship between CL(m) and CL(Cr) was observed in group 1 (r = 0.72, P < 0.001). The application of the formula to meropenem dosing in group 2, infusion rate (g/24 h) = [0.078 × CL(Cr) (ml/min) + 2.85] × target C(ss) × (24/1,000), led to a significant correlation between the observed and the predicted C(ss)s (r = 0.92, P < 0.001). Dosing nomograms based on CL(Cr) were created to target the meropenem C(ss) at 8, 12, and 16 mg/liter in critically ill patients. These nomograms could be helpful in improving the treatment of severe Gram-negative infections with meropenem, especially in the presence of borderline susceptible pathogens or even of carbapenemase producers and/or of pathophysiological conditions which may enhance meropenem clearance.

Successful long-term treatment of cerebral nocardiosis with unexpectedly low doses of linezolid in an immunocompromised patient receiving complex polytherapy.

Cerebral nocardiosis is a severe infection that carries the highest mortality rate among all bacterial cerebral abscesses. We report on a case in an immunocompromised patient which was successfully treated with unexpectedly low doses of linezolid. Therapeutic drug monitoring was very helpful in highlighting issues of poor compliance and of drug-drug interactions.

Therapeutic drug monitoring may improve safety outcomes of long-term treatment with linezolid in adult patients.

OBJECTIVES: Prolonged treatment with linezolid may cause toxicity. The purpose of this study was to define pharmacodynamic thresholds for improving safety outcomes of linezolid. METHODS: We performed a retrospective study of patients who had trough (C(min)) and peak (C(max)) plasma levels measured during prolonged linezolid treatment. Dosage adjustments were performed when C(min) ≥10 mg/L and/or AUC24 ≥400 mg/L ·â€Šh. Patients were divided into two subgroups according to the absence or presence of co-treatment with rifampicin (the linezolid group and the linezolid + rifampicin group, respectively). Data on demographic characteristics, disease, microbiology and haematochemical parameters were collected and outcomes in relation to drug exposure were compared between groups. RESULTS: A total of 45 patients were included. Dosage adjustments were needed in 40% versus 0% of patients in the linezolid group (n = 35) versus the linezolid + rifampicin group (n = 10), respectively. Patients in the linezolid group had either significantly higher C(min) [3.71 mg/L (1.43-6.38) versus 1.37 mg/L (0.67-2.55), P < 0.001] or AUC24 [212.77 mg/L ·â€Šh (166.67-278.42) versus 123.33 mg/L ·â€Šh (97.36-187.94), P < 0.001]. Thrombocytopenia appeared in 51.4% versus 0% of cases in the linezolid group versus the linezolid + rifampicin group, respectively. In 33.3% of those patients who were experiencing thrombocytopenia, therapeutic drug monitoring (TDM)-guided dosage reductions allowed recovery from toxicity and prosecution of therapy with good outcome. A logistic regression model for thrombocytopenia estimated a probability of 50% in the presence of C(min) of 6.53 mg/L and/or of AUC24 of 280.74 mg/L ·â€Šh. CONCLUSIONS: Maintenance over time of C(min) between 2 and 7 mg/L and/or of AUC24 between 160 and 300 mg/L ·â€Šh may be helpful in improving safety outcomes while retaining appropriate efficacy in adult patients receiving prolonged linezolid treatment.

TDM-guided therapy with daptomycin and meropenem in a morbidly obese, critically ill patient.

OBJECTIVE: To describe a case of severe cellulitis, successfully treated with high-dose daptomycin plus continuous infusion meropenem, in a patient with morbid obesity and renal failure, in whom drug exposure over time was optimized by means of real-time therapeutic drug monitoring (TDM). CASE SUMMARY: A 63-year-old man with morbid obesity (body mass index 81.6 kg/m²) and renal failure was admitted to the emergency department because of severe cellulitis. The patient had an admission Laboratory Risk Indicator for Necrotizing Fasciitis score of 9, and broad-spectrum antimicrobial therapy with daptomycin and meropenem was started. Because of rapidly changing renal function, dosage adjustments were guided by an intensive program of TDM (daptomycin ranging from 1200 mg every 48 hours over 30 minutes to 1200 mg every 36 hours over 30 minutes; meropenem ranging from 0.25 g every 8 hours over 6 hours to 500 mg every 4 hours by continuous infusion). Clinical response was observed within 72 hours. However, a sudden increase of serum creatine kinase (SCK) raised questions about the need for discontinuation of daptomycin. The drug concentrations were not toxic; therefore, we decided to continue therapy. Significant clinical improvement, with SCK normalization, was observed within a few days. Antimicrobial therapy was switched on day 29 to amoxicillin/clavulanate plus levofloxacin, and then discontinued at discharge on day 53. DISCUSSION: High-dose daptomycin plus continuous infusion meropenem may ensure adequate empiric antimicrobial coverage in patients with possible early necrotizing fasciitis. However, in patients with morbid obesity and changing renal function, significant challenges may arise because of the hydrophilic nature of these drugs and the inaccuracy of standard methods of estimating renal function. CONCLUSIONS: Real-time TDM may represent an invaluable approach in optimizing drug exposure with high-dose daptomycin plus continuous infusion meropenem in patients with severe cellulitis, morbid obesity, and changing renal function.

Therapeutic drug monitoring of linezolid: a retrospective monocentric analysis.

The objective of the present retrospective observational study carried out in patients receiving a standard dosage of linezolid and undergoing routine therapeutic drug monitoring (TDM) was to assess the interindividual variability in plasma exposure, to identify the prevalence of attainment of optimal pharmacodynamics, and to define if an intensive program of TDM may be warranted in some categories of patients. Linezolid plasma concentrations (trough [C(min)] and peak [C(max)] levels) were analyzed by means of a high-performance liquid chromatography (HPLC) method, and daily drug exposure was estimated (daily area under the plasma concentration-time curve [AUC(24)]). The final database included 280 C(min) and 223 C(max) measurements performed in 92 patients who were treated with the fixed 600-mg dose every 12 h (q12h) intravenously (n = 58) or orally (n = 34). A wide variability was observed (median values [interquartile range]: 3.80 mg/liter [1.75 to 7.53 mg/liter] for C(min), 14.70 mg/liter [10.57 to 19.64] for C(max), and 196.08 mg·h/liter [144.02 to 312.10 mg·h/liter] for estimated AUC(24)). Linezolid C(min) was linearly correlated with estimated AUC(24) (r(2) = 0.85). Optimal pharmacodynamic target attainment (defined as C(min) of ≥2 mg/liter and/or AUC(24)/MIC(90) ratio of >80) was obtained in about 60 to 70% of cases, but potential overexposure (defined as C(min) of ≥10 mg/liter and/or AUC(24) of ≥400 mg·h/liter) was documented in about 12% of cases. A significantly higher proportion of cases with potential overexposure received cotreatment with omeprazole, amiodarone, or amlodipine. Our study suggests that the application of TDM might be especially worthwhile in about 30% of cases with the intent of avoiding either the risk of dose-dependent toxicity or that of treatment failure.

Prospectively validated dosing nomograms for maximizing the pharmacodynamics of vancomycin administered by continuous infusion in critically ill patients.

The efficacy of vancomycin against methicillin-resistant Staphylococcus aureus (MRSA)-related infections has been called into question by recent findings of higher rates of failure of vancomycin treatment of infections caused by strains with high MICs. Continuous infusion may be the best way to maximize the time-dependent activity of vancomycin. The aim of this study was to create dosing nomograms in relation to different creatinine clearance (CL(Cr)) estimates for use in daily clinical practice to target the steady-state concentrations (C(ss)s) of vancomycin during continuous infusion at 15 to 20 mg/liter (after the administration of an initial loading dose of 15 mg/kg of body weight over 2 h). The correlation between vancomycin clearance (CL(v)) and CL(Cr) was retrospectively assessed in a cohort of critically ill patients (group 1, n = 70) to create a formula for dosage calculation to target C(ss) at 15 mg/liter. The performance of this formula was prospectively validated in a similar cohort (group 2, n = 63) by comparison of the observed and the predicted C(ss)s. A significant relationship between CL(v) and CL(Cr) was observed in group 1 (P < 0.001). The application of the calculated formula to vancomycin dosing in group 2 {infusion rate (g/24 h) = [0.029 x CL(Cr) (ml/min) + 0.94] x target C(ss) x (24/1,000)} led to a significant correlation between the observed and the predicted C(ss)s (r = 0.80, P < 0.001). Two dosing nomograms based on CL(Cr) were created to target the vancomycin C(ss) at 15 and 20 mg/liter in critically ill patients. These nomograms could be helpful in improving the vancomycin treatment of MRSA infections, especially in the presence of borderline-susceptible pathogens and/or of pathophysiological conditions which may enhance the clearance of vancomycin, while potentially avoiding the increased risk of nephrotoxicity observed with the use of high intermittent doses of vancomycin.

Biliary penetration and pharmacodynamic exposure of linezolid in liver transplant patients.

OBJECTIVES: The aim of the study was to assess the biliary penetration of linezolid and the probabilities of attaining optimal pharmacodynamic exposure against vancomycin-resistant enterococci (VRE) in the bile of liver transplant (LTx) patients who received linezolid for the treatment of multidrug-resistant Gram-positive hospital infections. METHODS: After at least 2 days of standard 600 mg twice-daily therapy, simultaneous bile and blood samples for linezolid assay were collected from six LTx patients just prior to drug administration to determine trough concentrations (Cmin) at steady-state in both sites. Linezolid concentrations in plasma and in bile were analysed by means of HPLC. Biliary penetration of linezolid was calculated as the ratio between Cmin in bile and in plasma. Optimal theoretical pharmacodynamic exposure of linezolid against VRE in bile was defined as biliary Cmin>MIC90. RESULTS: C(min) of linezolid in bile achieved very high values at steady-state, which were significantly higher than in plasma (median of 21.77 versus 8.08 mg/L, P=0.021). The very high biliary penetration of linezolid (median value of 1.93; range 1.31-4.83) enabled achievement of optimal theoretical pharmacodynamic exposure against VRE in bile (Cmin>2 mg/L) on all of the occasions. CONCLUSIONS: These preliminary data suggest a potential role for linezolid in the treatment of cholangitis due to VRE in LTx patients. Obviously, further confirmatory data assessing also the AUC/MIC ratio of linezolid in bile are needed.

A simple method to monitor serum concentrations of fluoxetine and its major metabolite for pharmacokinetic studies.

A rapid, selective and sensitive isocratic reversed-phase HPLC assay coupled with MS/MS detection for simultaneous quantification of fluoxetine and its major active metabolite in serum samples has been developed. Analytes were extracted with a simple three step liquid-liquid procedure and chromatographic separation was achieved on a C18 column. Because of its sensitivity, this HPLC/MS/MS method is suitable both for routine therapeutic drug monitoring and for pharmacokinetic studies, due to its low limits of quantification.

Drop in trough blood concentrations of tacrolimus after switching from nelfinavir to fosamprenavir in four HIV-infected liver transplant patients.

Solid organ transplantation in HIV-infected individuals requires concomitant use of immunosuppressants and antiretrovirals that may cause significant drug interactions. Here we report on a peculiar pharmacokinetic interaction between tacrolimus and protease inhibitors (PIs) which occurred in four HIV-infected liver transplant patients who had to shift PI therapy from nelfinavir to fosamprenavir as a consequence of regulatory restrictions. After the switch, tacrolimus trough blood concentrations significantly dropped in all patients (mean +/- SD 6.9 +/- 2.6 versus 3.2 +/- 2.0 ng/ml before and after the switch, respectively; P=0.01), so that a marked dosage increase was needed (0.29 +/- 0.14 versus 0.88 +/- 0.48 mg/day, 1-3 days before and 3 weeks after the switch, respectively; P=0.046) to attain the desired target (8.7 +/- 2.3 ng/ml). Consistently, marked changes of the concentration/dose ratio of tacrolimus were observed in all cases (27.2 +/- 9.7 ng/ml per mg/kg/day versus 9.7 +/- 4.0 ng/ml per mg/kg/day before and after the switch, respectively; P<0.001). Our findings suggest that fosamprenavir may be less potent than nelfinavir in inhibiting tacrolimus clearance and support the need for higher tacrolimus dosage to avoid insufficient immunosuppression in HIV-infected liver transplant patients when switching from nelfinavir to fosamprenavir or even when directly starting antiretroviral therapy with fosamprenavir.

Clinical relevance of pharmacokinetics and pharmacodynamics in cardiac critical care patients.

Pharmacokinetics is a discipline aimed at predicting the best dosage and dosing regimen for each single drug in order to ensure and maintain therapeutically effective concentrations at the action sites. In cardiac critical care patients, various pathophysiological conditions may significantly alter the pharmacokinetic behaviour of drugs. Gastrointestinal drug absorption may be erratic and unpredictable in the early postoperative period, and so patients may be unresponsive to oral therapy; thus the intravenous route should be preferred for life-saving drugs whenever feasible. Variations in the extracellular fluid content as a response to the trauma of surgery and the fluid load or significant drug loss through thoracic drainages may significantly lower plasma concentrations of extracellularly distributed hydrophilic antimicrobials (beta-lactams, aminoglycosides and glycopeptides). Drug metabolism may be altered by the systemic inflammatory response and/or multiple organ failure and/or drug-drug pharmacokinetic interactions that can potentially occur during polytherapy, especially in immunosuppressed cardiac transplant patients. Instability of renal function may promote significant changes in body fluid concentrations of renally eliminated drugs, even in a brief period of hours. Finally, the application of extracorporeal circulation by means of cardiopulmonary bypass may significantly alter the disposition of several drugs during the operation because of acute haemodilution, hypoalbuminaemia, hypothermia and/or adsorption to the bypass equipment. Accordingly, to avoid either overexposure and the consequent increased risk of toxicity or underexposure and the consequent risk of therapeutic failure in critically ill cardiac patients, the dosing regimens of several drugs are expected to be significantly different from those suggested for clinically stable patients. Additionally, therapeutic drug monitoring may be helpful in the management of drug therapy and should be routinely used to guide individualized dose adjustments for (i) immunosuppressants whenever cytochrome P450 3A4 isoenzyme inhibitors (e.g. macrolide antibacterials, azole antifungals) or inducers (e.g. rifampicin [rifampin]) are added to or withdrawn from the regimen; and (ii) glycopeptide and aminoglycoside antibacterials whenever haemodynamically active agents (such as dopamine, dobutamine and furosemide [frusemide]) are added to or withdrawn from the regimen, and also whenever significant changes of haemodynamics and/or of renal function occur.

Pharmacokinetic interaction between everolimus and antifungal triazoles in a liver transplant patient.

OBJECTIVE: To describe the management of a pharmacokinetic interaction between azole antifungals (fluconazole and voriconazole) and everolimus in a patient who underwent an orthotopic liver transplant. CASE SUMMARY: A 65-year-old male who received an orthotopic liver transplant experienced an iatrogenic retroperitoneal duodenal perforation on postoperative day 55. His condition was subsequently complicated by severe sepsis and acute renal failure. Intravenous fluconazole 400 mg, followed by 100 mg every 24 hours according to impaired renal function, was immediately started; to avoid further nephrotoxicity, immunosuppressant therapy was switched from cyclosporine plus mycophenolate mofetil to oral everolimus 0.75 mg every 12 hours. Satisfactory steady-state minimum concentration (C(min)) of everolimus was achieved (approximately 5 ng/mL). On day 72 posttransplant, because of invasive aspergillosis, antifungal therapy was switched to intravenous voriconazole 400 mg every 12 hours on the first day, followed by 200 mg every 12 hours; to prevent drug toxicity, the everolimus dosage was promptly lowered to 0.25 mg every 24 hours. At that time, the everolimus C(min) averaged approximately 3 ng/mL. The concentration/dose ratio of everolimus (ie, C(min) reached at steady-state for each milligram per kilogram of drug administered) was markedly lower during fluconazole versus voriconazole cotreatment (mean +/- SD, 3.49 +/- 0.29 vs 11.05 +/- 0.81 ng/mL per mg/kg/daily; p < 0.001). Despite intensive care, the patient's condition continued to deteriorate and he died on day 84 posttransplant. DISCUSSION: Both azole antifungals were considered probable causative agents of an interaction with everolimus according to the Drug Interaction Probability Scale. The interaction is due to the inhibition of CYP3A4-mediated everolimus clearance. Of note, prompt reduction of the everolimus dosage since the first azole coadministration, coupled with intensive therapeutic drug monitoring, represented a useful strategy to prevent drug overexposure. CONCLUSIONS: Our data suggest that during everolimus-azole cotreatment, a dose reduction of everolimus is needed to avoid overexposure. According to the different inhibitory potency of CYP3A4 activity, the reduction should be lower during fluconazole than during voriconazole cotreatment.

Pharmacokinetic considerations for antimicrobial therapy in patients receiving renal replacement therapy.

Continuous renal replacement therapy (CRRT), particularly continuous venovenous haemofiltration (CVVH) and continuous venovenous haemodiafiltration (CVVHDF), are gaining increasing relevance in routine clinical management of intensive care unit patients. The application of CRRT, by leading to extracorporeal clearance (CL(CRRT)), may significantly alter the pharmacokinetic behaviour of some drugs. This may be of particular interest in critically ill patients presenting with life-threatening infections, since the risk of underdosing with antimicrobial agents during this procedure may lead to both therapeutic failure and the spread of breakthrough resistance. The intent of this review is to discuss the pharmacokinetic principles of CL(CRRT) of antimicrobial agents during the application of CVVH and CVVHDF and to summarise the most recent findings on this topic (from 1996 to December 2006) in order to understand the basis for optimal dosage adjustments of different antimicrobial agents. Removal of solutes from the blood through semi-permeable membranes during RRT may occur by means of two different physicochemical processes, namely, diffusion or convection. Whereas intermittent haemodialysis (IHD) is essentially a diffusive technique and CVVH is a convective technique, CVVHDF is a combination of both. As a general rule, the efficiency of drug removal by the different techniques is expected to be CVVHDF > CVVH > IHD, but indeed CL(CRRT) may vary greatly depending mainly on the peculiar physicochemical properties of each single compound and the CRRT device's characteristics and operating conditions. Considering that RRT substitutes for renal function in clearing plasma, CL(CRRT) is expected to be clinically relevant for drugs with dominant renal clearance, especially when presenting a limited volume of distribution and poor plasma protein binding. Consistently, CL(CRRT) should be clinically relevant particularly for most hydrophilic antimicrobial agents (e.g. beta-lactams, aminoglycosides, glycopeptides), whereas it should assume much lower relevance for lipophilic compounds (e.g. fluoroquinolones, oxazolidinones), which generally are nonrenally cleared. However, there are some notable exceptions: ceftriaxone and oxacillin, although hydrophilics, are characterised by primary biliary elimination; levofloxacin and ciprofloxacin, although lipophilics, are renally cleared. As far as CRRT characteristics are concerned, the extent of drug removal is expected to be directly proportional to the device's surface area and to be dependent on the mode of replacement fluid administration (predilution or postdilution) and on the ultrafiltration and/or dialysate flow rates applied.Conversely, drug removal by means of CVVH or CVVHDF is unaffected by the drug size, considering that almost all antimicrobial agents have molecular weights significantly lower (<2000Da) than the haemofilter cut-off (30,000-50,000Da). Drugs that normally have high renal clearance and that exhibit high CL(CRRT) during CVVH or CVVHDF may need a significant dosage increase in comparison with renal failure or even IHD. Conversely, drugs that are normally nonrenally cleared and that exhibit very low CL(CRRT) during CVVH or CVVHDF may need no dosage modification in comparison with normal renal function. Bearing these principles in mind will almost certainly aid the management of antimicrobial therapy in critically ill patients undergoing CRRT, thus containing the risk of inappropriate exposure. However, some peculiar pathophysiological conditions occurring in critical illness may significantly contribute to further alteration of the pharmacokinetics of antimicrobial agents during CRRT (i.e. hypoalbuminaemia, expansion of extracellular fluids or presence of residual renal function). Accordingly, therapeutic drug monitoring should be considered a very helpful tool for optimising drug exposure during CRRT.

Major role of levofloxacin in the treatment of a case of Listeria monocytogenes meningitis.

We report a case of acute bacterial meningitis due to Listeria monocytogenes whose successful treatment was mainly attributable to high-dose levofloxacin therapy (500 mg iv bid). This supports the hypothesis that levofloxacin may be an effective option for the treatment of listerial meningitis.

Chronopharmacokinetics of ciclosporin and tacrolimus.

The correct use of immunosuppressive drugs has a considerable influence on the prognosis of patients with organ transplants. The appropriate utilisation of the drugs involves the administration of an adequate dosage to reach the blood concentrations that will suppress the alloimmune response, while avoiding secondary toxicities. However, transplanted patients exhibit heterogeneous immunological responses and high inter- and intraindividual pharmacokinetic variabilities. One cause of these variabilities that is rarely considered is circadian rhythms. In vitro and in vivo experiments have clearly demonstrated that all organisms are highly organised according to an internal biological clock that influences various physiological functions. Considering that the absorption, distribution, metabolism and elimination of drugs is influenced by the physiological functions of the body, it is not surprising that the pharmacokinetic, and consequently the pharmacodynamic, profiles of drugs can be influenced by circadian rhythms. Ciclosporin, a mainstay immunosuppressive drug used following organ transplantation, displays minimum blood concentration (C(min)), maximum blood concentration (C(max)) and area under the blood concentration-time curve (AUC) in the morning that are generally higher than the corresponding parameters in the evening. These observations are supported by the ciclosporin total body clearance and elimination half-life in the morning, which are, on average, higher and shorter, respectively, than those in the evening. In addition, the disposition of tacrolimus is determined by the time of administration. The tacrolimus C(max) and AUC after the morning dose are significantly higher than those after the evening dose. Finally, the results reported in this review suggest considering more carefully the chronopharmacokinetics of tacrolimus and ciclosporin in order to obtain better results with fewer adverse effects. Significantly, the morning appears to be the best time for therapeutic monitoring using the C(min), C(max), concentration at 2 hours after dosing and AUC to modify dosages of tacrolimus and ciclosporin. Less certain are any conclusions about whether, in order to obtain better immunosuppressive control, higher doses must be administered when these drugs are given in the evening to compensate for the higher levels of interleukin-2.

Pharmacokinetic and pharmacodynamic aspects of oral moxifloxacin 400 mg/day in elderly patients with acute exacerbation of chronic bronchitis.

OBJECTIVE: To assess the pharmacokinetic and pharmacodynamic behaviour of moxifloxacin in 15 consecutive elderly patients with acute exacerbation of chronic bronchitis (AECB) treated with the fixed oral moxifloxacin 400 mg/day regimen with the intent of verifying which degree of exposure may be ensured by this standard regimen against AECB pathogens. METHODS: This was an open-label, observational, pharmacokinetic-pharmacodynamic study. Blood samples were collected at steady state at appropriate intervals. Moxifloxacin plasma concentrations were analysed by means of high-performance liquid chromatography. Standard pharmacokinetic parameters and pharmacodynamic determinants (peak concentration [C(max)]/minimum inhibitory concentration [MIC], area under the plasma concentration-time curve during the 24-hour observational period [AUC(24)]/MIC, pharmacodynamic breakpoints [PDBPs]) were assessed. RESULTS: The mean estimated pharmacokinetic parameters (C(max) 4.40 mg/L at 1.4 hours, AUC(24) 42.67 mg . h/L, elimination half-life 12.55 hours, total body clearance 0.16 L/h/kg) were generally similar to those observed in both young and elderly historic controls (except for higher-dose normalised C(max) and lower volume of distribution of the central compartment). Median C(max)/MIC and AUC(24)/MIC ratios for moxifloxacin in the fully assessable cases were, respectively, 67.5 and 823.9 against Streptococcus pneumoniae, 25 and 310.2 against Moraxella catharralis and 416.5 and 3647.5 against Haemophilus influenzae. Mean estimates of PDBP for achieving C(max)/MIC values of 12.2 and AUC(24)/MIC values of 125 were 0.36 and 0.35 mg/L, respectively. CONCLUSION: In patients with AECB the pharmacokinetic behaviour of moxifloxacin is not significantly altered by aging processes. This is consistent with moxifloxacin being metabolised mainly by means of phase II hepatic reactions, the activity of which was shown not to decline with age. Both the pharmacokinetic and pharmacodynamic analyses suggest that moxifloxacin 400 mg/day may be a valid therapeutic approach in the treatment of AECB in the elderly. Of note, the unmodified pharmacokinetic behaviour with no need for age-related dosage adjustments combined with the once-daily administration favouring compliance and the low potential for drug-drug pharmacokinetic interactions in case of polytherapy, make moxifloxacin particularly attractive in the treatment of elderly subpopulations at a very high risk of AECB.

The effect of multifactorial, multidisciplinary educational interventions on appropriate use of teicoplanin.

The aim of this study was to determine the effect of multifactorial, multidisciplinary educational interventions over a 3-year period on the appropriate use of teicoplanin. Teicoplanin was considered a valid surrogate marker of good antibiotic use in clinical practice owing to its peculiar pharmacokinetics (i.e. necessity for an initial loading dose regardless of the patient's renal function for early achievement of optimal exposure, namely C(min) > or = 10 mg/L) and to the opportunity of comparing current routine therapeutic drug monitoring (TDM) results with those of a historical retrospective study. A significantly higher proportion of patients received appropriate loading doses of teicoplanin in the present prospective study than in the retrospective study, both when considered as a whole (66.6% versus 38.6%, respectively; P<0.001) or when stratified according to the degree of estimated renal function (78.4% versus 60.4% for creatinine clearance (CL(Cr)) > 50 mL/min; 59.8% versus 26.8% for CL(Cr) 20-50 mL/min; and 27.7% versus 5.5% for CL(Cr) <20 mL/min). The highest adherence was observed in haematological wards (97.7%). The percentages of patients with teicoplanin C(min) > or = 10 mg/L during the treatment period in the present and retrospective study, respectively, were: 61.4% versus 3.2% on Day 2; 88% versus 35% on Day 4; 94% versus 70% on Day 7; and 99% versus 90% on Day 11. Our findings suggest that continuous application of a multifactorial educational programme including active TDM may be efficacious in improving and maintaining over time the appropriate use in a hospital setting of a theoretically difficult-to-use drug such as teicoplanin.

Pharmacokinetic-pharmacodynamic aspects of antimicrobial prophylaxis with teicoplanin in patients undergoing major vascular surgery.

A prospective, two-arm, open study assessing plasma exposure to teicoplanin with two different prophylactic regimens (Group A (n = 23), 800 mg pre-operatively versus Group B (n = 24), 400 mg pre-operatively plus two doses of 200 mg 24 h apart) was carried out in patients undergoing major vascular surgery. The intent was to define the feasibility and the possible advantages of the single pre-operative high dose in ensuring therapeutically effective plasma concentrations (>10 mg/L) of teicoplanin even during long-lasting operations. At the end of the intervention, mean teicoplanin concentrations (+/-S.D.) were 14.05 +/- 5.13 mg/L and 5.39 +/- 2.13 mg/L in Groups A and B, respectively. At 24 h, average teicoplanin levels were 5.10 +/- 1.25 mg/L and 2.08 +/- 0.73 mg/L in Groups A and B, respectively; at 48 h they declined to 2.86 +/- 0.70 mg/L in Group A, whereas they rose to 2.67 +/- 0.82 mg/L after administration of 2.63 +/- 0.51 mg/kg at 24 h in Group B. Single pre-operative high-dose teicoplanin may ensure effective plasma levels even in cases of very long-lasting operations (>8 h) with no need for intraoperative re-dosing and may enable more appropriate prophylactic exposure than that achievable with the same total dose given in three administrations 24 h apart.

Antimicrobial therapy in critically ill patients: a review of pathophysiological conditions responsible for altered disposition and pharmacokinetic variability.

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients. Selecting the appropriate antimicrobial at the commencement of therapy, both in terms of spectrum of activity and dose and frequency of administration according to concentration or time dependency, is mandatory in this setting. Despite appropriate standard dosage regimens, failure of the antimicrobial treatment may occur because of the inability of the antimicrobial to achieve adequate concentrations at the infection site through alterations in its pharmacokinetics due to underlying pathophysiological conditions. According to the intrinsic chemicophysical properties of antimicrobials, hydrophilic antimicrobials (beta-lactams, aminoglycosides, glycopeptides) have to be considered at much higher risk of inter- and intraindividual pharmacokinetic variations than lipophilic antimicrobials (macrolides, fluoroquinolones, tetracyclines, chloramphenicol, rifampicin [rifampin]) in critically ill patients, with significant frequent fluctuations of plasma concentrations that may require significant dosage adjustments. For example, underexposure may occur because of increased volume of distribution (as a result of oedema in sepsis and trauma, pleural effusion, ascites, mediastinitis, fluid therapy or indwelling post-surgical drainage) and/or enhanced renal clearance (as a result of burns, drug abuse, hyperdynamic conditions during sepsis, acute leukaemia or use of haemodynamically active drugs). On the other hand, overexposure may occur because of a drop in renal clearance caused by renal impairment. Care with all these factors whenever choosing an antimicrobial may substantially improve the outcome of antimicrobial therapy in critically ill patients. However, since these situations may often coexist in the same patient and pharmacokinetic variability may be unpredictable, the antimicrobial policy may further benefit from real-time application of therapeutic drug monitoring, since this practice, by tailoring exposure to the individual patient, may consequently be helpful both in improving the outcome of antimicrobial therapy and in containing the spread of resistance in the hospital setting.