Gentamicin

C. diff Risk

Low

Oral Bioavailability

NA

Approximate Cost

$10-30/d

Dosing

Adult

High Dose Extended Interval (HDEI)
5-7mg/kg IV q24h

Conventional Dosing
1.5-2mg/kg IV q8h

Enterococcal Synergy
1 mg/kg IV q8h

N.B. use Dosing Weight (aka. Adjusted Body Weight) for obese patients

General Information

Common Usage

Targeted therapy for suspected or confirmed multidrug resistant gram negative infections.

Used synergistically in enterococcal endocarditis.

Drug Monitoring

Consult clinical pharmacy for level interpretation and dosing.

Monitor creatinine at least 3 times/week. Discontinue if any signs of ototoxicity.

HDEI Dosing
Target trough <1mcg/mL

Conventional Dosing
Peak monitoring poorly supported by literature, but target peak 4-10mcg/mL; trough 1-2mcg/mL only if using >4 days

NB: trough level is 0-60min before a dose (usually pre-4th), and peak is 30-60min after dose infused (usually post-3rd).

In critically ill patients, consider checking peak level after the 1st dose as volume of distribution and renal function may change rapidly.

Adverse Effects

Nephrotoxicity (non-oliguric)

  •  Avoid concomitant nephrotoxins

  •  Less common with HDEI 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

  •  Vancomycin

  •  Cyclosporin

  •  NSAIDs

  •  Contrast

Increased ototoxicity

  •  Loop diuretics (e.g. furosemide)

Increased risk of respiratory paralysis

  •  Neuromuscular blockade agents

Additional Information

Formal audiology assessment at baseline if planning to use aminoglycoside for >7d or if symptoms develop.

Inform patient of risk of ototoxicity and to report any symptoms (oscillopsia, imbalance, hearing loss, tinnitus).

Pharmacology

Antimicrobial class: Aminoglycoside

Pregnancy category: D

Average serum half life: 2.0

Biliary penetration: Moderate

CSF penetration: Poor

Lung penetration: Therapeutic

Urine penetration: Therapeutic