Gentamicin Synergy

C. diff Risk

Low

Oral Bioavailability

NA

Approximate Cost

Dosing

General Information

Common Usage

Used synergistically in enterococcal endocarditis

Drug Monitoring

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

Synergy dosing:

  •  Target trough: less than 1mg/L

  •  Target peak: 3-4mg/L

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, check 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 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

  •  Vancomycin

  •  Cyclosporin

  •  NSAIDs

  •  Contrast

Increased ototoxicity

  •  Loop diuretics (e.g. furosemide)

Non-depolarizing muscle relaxants may be potentiated

Pharmacology

Antimicrobial class: Aminoglycoside

Pregnancy category: D

Average serum half life: 2 hours

Biliary penetration: Moderate

CSF penetration: Poor