Definition
- Antibiotics are substances that destroy or inhibit the growth of microorganisms. Antibiotics consist of chemical groups such as Ž ²-lactams, polyenes, macrolides, tetracyclines, aminoglycosides, and sulfonamides. Names include amikacin, chloramphenicol, gentamicin, kanamycin, streptomycin, tobramycin, and vancomycin.
- Normal therapeutic (and toxic) levels: see Table 16.5.
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TABLE 16 " “5Therapeutic and Toxic Serum Concentrations for AntibioticsView LargeTABLE 16 " “5Therapeutic and Toxic Serum Concentrations for Antibiotics Therapeutic Concentration ( ‚ µmg/mL) Potentially Toxic Level ( ‚ µg/mL) Amikacin " ƒPeak 15 " “25 >30 " ƒTrough 2 " “5 >8 Chloramphenicol " ƒPeak 10 " “20 25 " ƒTrough 5 " “10 15 Gentamicin " ƒPeak 5 " “10 12 " ƒTrough 0.5 " “2 >2 Kanamycin " ƒPeak 20 " “25 " ƒTrough 5 " “10 Netilmicin " ƒPeak 4 " “8 8 " ƒTrough 1 " “2 2 Streptomycin " ƒPeak 5 " “20 40 " ƒTrough <5 40 Tobramycin " ƒPeak 5 " “10 12 " ƒTrough 0.5 " “2 >2 TMP/SMX " ƒPeak (TMP) 4 " “8 8 " ƒPeak (SMX) 1 " “2 >2 Vancomycin " ƒPeak (not recommended) 30 " “40 >80 " ƒTrough 5 " “10 >20
Use
- Prevention and treatment of infections caused by bacteria
Limitations
- Testing must be performed on serum or plasma.
- Peak concentrations: collect specimen 30 " “120 minutes after completion of infusion (drug and route dependent).
- Trough concentrations: collect specimen 5 " “90 minutes before next infusion (drug dependent).
- Testing methodologies: immunoassay (e.g., fluorescence polarization) or HPLC.
- Specimens must be frozen for streptomycin and amphotericin B.
- Specimens must be protected from light for trimethoprim and amphotericin.
- Unacceptable specimens:
- Hemolyzed
- Collection tubes with additives such as serum separator, citrate, oxalate, or fluoride
- Trimethoprim may be detected in urine in general toxicology screens utilizing GC/MS.