Gentamicin Synergy

C. diff Risk


Oral Bioavailability



3mg/kg (S. viridans endocarditis)


Note, the choice of the dosing interval is based on the patient's renal function.

The patient's urinary output should be considered in addition to the serum creatinine concentration.

  • CrCl Greater Than 70 mL/min: Q8h

  • CrCl 40-69 mL/min: Q12h

  • CrCl 20-39 mL/min: Q24h

  • CrCl Less Than 20 mL/min: Give a dose and draw levels in 24 hours to determine dosing interval.

General Information

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.

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

Increased nephrotoxicity

  •  Amphotericin

  •  Vancomycin

  •  Cyclosporin

  •  NSAIDs

  •  Contrast

Increased ototoxicity

  •  Loop diuretics (e.g. furosemide)

Non-depolarizing muscle relaxants may be potentiated

Antimicrobial class: Aminoglycoside

Pregnancy category: D

Average serum half life: 2 hours

Biliary penetration: Moderate

CSF penetration: Poor

Used synergistically in enterococcal endocarditis