Tobramycin

C. diff Risk

Low

Oral Bioavailability

NA

Approximate Cost

Dosing

Adult

Once Daily/Extended Interval Dosing
7mg/kg dosing body weight (DBW) IV q24h

Multiple Daily Dosing
1.5-2mg/kg dosing body weight (DBW) loading dose then 1.5 mg/kg DBW IV q8h

DBW = Dosing body weight. See Additional information

General Information

Common Usage

Pseudomonal and other gram negative infections.

Inhaled form used in cystic fibrosis.

Drug Monitoring

Monitor serum creatinine, BUN 2-3 times/week. Discontinue if any signs of ototoxicity.

For once daily/extended interval dosing dosing:

  • Peak levels are not recommended

  • NO level is required in patients with good renal function and therapy anticipated to be less than 8 days

  • Patient populations to consider a serum concentration independent of duration of therapy:

    • critically ill patients
    • rapidly changing renal status
    • increased or rapidly changing Vd (e.g. ascities, burn)
    • serum Cr unreliable indicator of renal function
    • concurrent nephrotoxic therapy (amphotericin B, vancomycin, chemotherapy, high furosemide, cyclosporine or tacrolimus etc.)

A single serum concentration can be drawn between 6 to 14 hours after the start of the aminoglycoside infusion (typically a 8-10 hour post concentration is drawn.)

  • Contact pharmacy for monitoring set up, level interpretation and dose individualization.

For conventional multiple times per day dosing:

  • Target Peak 3-10 mg/L, Trough <2 mg/L. Peak levels usually not required but if drawn, record time of dose and time of level draw as accurately as possible.

  • Contact pharmacy for monitoring set up, level interpretation and dose individualization

NB: Trough level is 30-60min BEFORE next dose dose, and peak is 30-60min AFTER dose infused.

For Intermittent OR Continuous dialysis:

  • Contact pharmacy for monitoring set up, level interpretation and dose individualization

Adverse Effects

Nephrotoxicity (non-oliguric)

  •  Avoid concomitant nephrotoxins

  •  Less common with once daily dosing

  •  Greater toxicity with longer duration and supratherapeutic trough levels

Vestibulocochlear toxicity

  • Irreversible

  • Require audiology testing if prolonged use

Can exacerbate neuromuscular blockade

  •  Contraindicated in patients with myasthenia gravis.

Major Interactions

Increased nephrotoxicity

  •  Amphotericin B

  •  Cyclosporine

  •  Cisplatin

  •  NSAIDS

  •  Contrast dye

  •  Vancomycin

Increased ototoxicity

  •  Furosemide

Neuromuscular blockade agents - Respiratory paralysis.

Additional Information

  • Perform baseline and ongoing weekly otovestibular toxicity assessment. Formal audiology assessment required if symptoms develop.

  • Inform patient of risk of ototoxicity and to report any symptoms.

Calculation of Dosing Body Weight (DBW)
DBW = IBW + [(ABW - IBW) x 0.4]

where:
IBW male = 50kg + 0.906kg [Height (cm) - 152.4cm]
IBW female = 45kg + 0.906kg [Height (cm) - 152.4cm]

Dosing Body Weight = DBW
Ideal Body Weight = IBW
Actual Body Weight = ABW

Pharmacology

Antimicrobial class: Aminoglycoside

Pregnancy category: D

Average serum half life: 3 hours

Biliary penetration: Moderate

Lung penetration: Therapeutic

Urine penetration: Therapeutic

CSF penetration: Poor