Serum concentration monitoring

Initial antibiotic choice should always cover gram-positive organisms (e.g., vancomycin 20 mg/kg intravenously with serum concentration monitoring or cefazolin 20 mg/kg intravenously 3 times... 

Gram-negative coverage is indicated for patients with diabetes, HIV infection, prosthetic valves, or those receiving immunosuppressive agents (gentamicin 2 mg/kg intravenously with serum concentration monitoring). 

For most antimicrobial agents, the relation between dose and therapeutic outcome is well established, and serum concentration monitoring is unnecessary for these drugs. To justify routine serum concentration monitoring, it should be established (1) that a direct relationship exists between drug concentrations and efficacy or toxicity (2) that substantial interpatient variability exists in serum concentrations on standard doses (3) that a small difference exists between therapeutic and toxic serum concentrations (4) that the clinical efficacy or toxicity of the drug is delayed or difficult to measure and (5) that an accurate assay is available. 

In clinical practice, serum concentration monitoring is routinely performed on patients receiving aminoglycosides. Despite the lack of supporting evidence for its usefulness or need, serum vancomycin concentration monitoring is also widespread. Flucytosine serum concentration monitoring has been shown to reduce toxicity when doses are adjusted to maintain peak concentrations below 100 mcg/mL. 

Chen K-P, Shen W, Lu M-L. Implication of serum concentration monitoring in patients with hthium intoxication. Psychiatry Clin Neurosci 2004 58 25-9. 

In contrast, other authors have stated that serum concentration monitoring is recommended during maintenance treatment with clozapine, in the light of a retrospective, open, non-randomized study in 86 patients, in which 404 serum concentrations were measured (310). Eight cases of intoxication were identified, and the conclusions were that the risk of toxicity is increased at serum concentrations over 750 ng/ml, while the risk of relapse is low at serum concentrations over 250 ng/ml, irrespective of concurrent psychotropic drugs, although intoxication was defined only according to the reason for the request for serum concentrations assay, as outlined in the request form. 

In a randomized, prospective, cost-effectiveness study both teicoplanin and vancomycin were assessed as second-line therapy in 66 neutropenic patients after the failure of empirical treatment with a combination of piperacillin -I- tazobactam and amikacin (10). The primary success of second-line therapy was equivalent, and the direct total costs were similar. Acquisition costs per dose were in favor of vancomycin, but costs derived from administering vancomycin and serum concentration monitoring led to similar costs for both regimens. With the exception of the red man syndrome, which occurred in 10% of vancomycin-treated patients but none of the tei-coplanin-treated patients, toxicity (renal, liver, and ear toxicity, diarrhea, phlebitis) was also similar. 

Hendeles L, Wemberger M. Theophylline Therapeutic use and serum concentration monitoring. In Taylor WJ, Finn AL, Eds. Individualizing drug therapy. New York Gross, Townsend, and Frank, 1981 32-65. 

Serum concentration monitoring of various drugs administered to pediatric patients may appropriately give information about the drug but not its metabolites. This may be a problem when children metabolize specific drugs differently than adults with resulting differences in metabolite concentrations or the presence of different metabolites. This has been noted when premature infants... 

Thus the ehmination of aminoglycosides in ESKD patients also receiving antipseudomonal penichlins will be increased therefore frequent serum concentration monitoring should be performed. To minimize any in vitro inactivation of aminoglycosides that would comphcate assessment of the in vivo effects, serum samples should be assayed as soon as possible after coUection. If this is not possible, serum samples should be frozen (preferably at-70°C, or-94°F) until they can be assayed. 

The role and necessity of AED serum concentration monitoring are controversial. Some clinicians feel that therapeutic blood level monitoring is essential for appropriate use of AEDs, whereas other feel that blood level monitoring is overused and, in many cases, unwarranted. AED blood level monitoring should be viewed as a tool to be used as part of overall AED treatment optimization. Acheivement of a specific "therapeutic" level should not be an absolute goal in and of itself. 

Vancomycin serum concentration monitoring can either be minimized or avoided entirely for many patients who are treated with this antimicrobial. 

The clinician should have an understanding of in vivo antimicrobial agent disposition in order to select the most appropriate therapy for a given infection and to help monitor for clinical or bacteri-ologic efficacy. Serum concentration monitoring is the most common method used to attempt to maximize efficacy and minimize toxicity of antimicrobials. Since most antimicrobials are well tolerated at their usual doses, only a select few agents (e.g., aminoglycosides, chloramphenicol, and vancomycin) are monitored routinely in the current clinical environment. There are a number of direct and indirect methods that are used to quantify the concentration of antimicrobial in an experimental sample. 

The aminoglycosides (i.e., amikacin, gentamicin, and tobramycin) and vancomycin remain the most common agents for which serum concentrations are monitored. A summary of the recommendations for serum concentration monitoring of these agents is shown in Table 103-2. 

Traditional methods of aminoglycoside serum concentration monitoring (evaluating peak and trough serum concentrations) cannot be applied to extended-interval dosing... 

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