Gentamicin Drug Monitoring

Note

Monitor creatinine at least weekly and more often if levels are elevated or other signs of renal dysfunction arise

Discontinue if any signs of ototoxicity (tinnitus, fullness in ears, dizziness)

Consult pharmacy for interpretation of concentrations

  • Less than or equal to 28 weekend and PNA less than or equal to 7 days

  • Weight less than or equal to 1250g

  • HIE

  • Concurrent nephrotoxic medications

  • Hemodynamic instability requiring vasoconstrictors

  • Renal dysfunction at start of therapy (urine output less than 1mL/kg/hr OR Scr increase of 30% of more from baseline)

Serum Concentration Monitoring

  • For most patients and indications, no concentrations are necessary, unless patient suspected at high risk for development of nephrotoxicity or renal dysfunction, or duration of treatment more than 5 days

    • In these cases check trough concentration prior to any dose to ensure that it is less than 1 mg/L
  • In cases where there is concern regarding treatment efficacy due to lack of response or severe infection treated with monotherapy, for cystic fibrosis (CF) or febrile neutropenia:

    • Draw TWO concentrations, one 2 to 3 hours and one 6 to 8 hours after first dose

Obtain drug concentrations with the third or fourth dose. Peak serum concentrations are drawn 30 minutes after the end of an IV infusion or one hour post-IM injection.

  • Peak concentrations: 5 to 10 mg/L and 12 to 15 mg/L in cystic fibrosis

  • Trough concentrations are drawn just prior to the next dose and should be less than 2 mg/L

Concentrations are typically not required

  • Peak target: 3 to 5 mg/L

  • Trough target: Less than 2 mg/L

Therapy less than 48 hours: No serum concentrations

Therapy greater than 48 hours + risk of gentamicin toxicity: Draw 22 hour post dose serum concentration and consult pharmacy

  • Serum concentrations should be drawn at least weekly thereafter

  • If 22 h concentration is:

    • 1.2 mg/L or less: Give q24h
    • 1.3 to 2.6 mg/L: Give q36h
    • 2.7 to 3.5 mg/L: Give q48h
    • 3.6 mg/L or more: Hold next dose, repeat concentration in 24 hours. Base interval on time to reach pre-dose concentration less than 2 mg/L

  • Serum concentrations should be drawn at least weekly

  • Pre-dose concentration should be drawn 0-30 minutes prior to dose

Goal pre-dose concentration:

  • Greater than 0.3mg/L to less than 2mg/L

If pre-dose concentration is:

  • Less than 0.3mg/L: Reduce dosing interval by 12 hours, if current interval is q24h, consider alternatives to extended interval dosing

  • Greater than 0.3mg/L to less than 2mg/L: Continue current regimen

  • 2-3mg/L: Increase interval by 12 hours. If current interval is q48h, do not give next dose and repeat concentration in 24 hours

  • Greater than 3mg/L: Do NOT give next dose and repeat concentration in 24 hours