Maintenance over time of C(min) between 2 and 7 mg/L and/or of AUC₂₄ between 160 and 300 mg/L · h may be helpful in improving safety outcomes while retaining appropriate efficacy in adult patients receiving prolonged linezolid treatment.

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 dos...

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.

Data obtained as part of our routine drug monitoring of teicoplanin therapy (therapeutic drug monitoring, TDM) in adult critically ill patients being treated for suspected or documented Grampositive multiresistant infections were assessed, retrospectively. Data were available for 202 patients (146 male, 56 female; age 58 ± 16 years) with a total number of 829 teicoplanin trough plasma levels (C min) assessed. The percentage of patients with adequate teicoplanin concentrations (C min ≥ 10 mg/L) during the treatment period substantially increased from 3.2% on day 2, to 35%, 70%, 90% and ∼95% on days 4, 7, 11 and 15, respectively. The findings suggest that optimal teicoplanin therapy was achieved only after at least 4, and probably 7, days of therapy in most cases, mainly because of a failure to use an appropriate loading dose. Among the possible causes for the reluctance to use a loading dose, concern over the potential nephrotoxicity of teicoplanin was a major factor. We conclude that loading doses of teicoplanin (6 mg/kg every 12 h for at least three doses) must be considered mandatory in all patients, regardless of their renal function, to enable optimal drug concentrations to be achieved early in the treatment period. Subsequently, TDM is important to ensure that dose regimens are optimized to the individual requirements of the patients.