Gentamicin

C. diff Risk

Low

Oral Bioavailability

NA

Approximate Cost

Dosing

Once daily dosing: 5-7mg/kg IV q24h Multiple daily dosing: 1.5-2mg/kg IV q8h N.B. use Dosing Weight (aka. Adjusted Body Weight) for obese patients Enterococcal synergy: 1 mg/kg IV q8h

General Information

Common Usage

Empiric (in combination) or targeted therapy for suspected or confirmed gram negative infections.

Empiric therapy for pyelonephritis.

Used synergistically in enterococcal endocarditis.

Drug Monitoring

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

Once daily dosing: target trough <1mcg/mL

Multiple daily 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, check peak level after the 1st dose as volume of distribution and renal function may change rapidly.

Adverse Effects

Nephrotoxicity (non-oliguric)- less common with once daily dosing; greater toxicity with longer duration and supratherapeutic trough levels; avoid concomitant nephrotoxins

Vestibulocochlear toxicity (irreversible)- require audiology testing if prolonged use

Can exacerbate neuromuscular blockade- e.g. contraindicated in patients with myasthenia gravis.

Major Interactions

Amphotericin, vancomycin, cyclosporin, NSAIDs, increased contrast-induced nephrotoxicity

Loop diuretics (e.g. furosemide)- increased ototoxicity

Non-depolarizing muscle relaxants may be potentiated

Additional Information

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

Inform patient of risk of ototoxicity to report any symptoms

Contraindicated in patients with myasthenia gravis

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