Gentamicin: once daily dosing (CWard Formulary)

Audience

• HHSCP only
• Paediatrics only

Indication

• Gentamicin is an aminoglycoside antibiotic with a broad spectrum of activity against some Gram-positive bacteria, many Gram-negative bacteria including Pseudomonas aeruginosa.
• Generally used as the first line aminoglycoside, except in cystic fibrosis.
• For obese patients (actual body weight >120% of the ideal body weight), use ideal body weight to calculate gentamicin doses. Extrapolate estimated IBW from the height centiles on the growth chart.

Exclusion

• Do not use in renal impairment, meningitis, endocarditis and burns.
• See multiple daily dosing regime.

Therapeutic drug monitoring

• Sample trough blood level between 18 and 24 hours AFTER END of first infusion.
• Aim for trough <1mg/L.
• If levels satisfactory, repeat after 3 to 4 days, or sooner if clinically indicated eg change in renal function. See note below on duration of treatment.
• If levels unsatisfactory seek advice from the clinical pharmacist or microbiology on dose or interval adjustment and re-sample BEFORE the third dose.

Supply

• 20mg in 2mL or 80mg in 2mL vials/ampoules.

Preparation

• Give as an IV infusion over 60 minutes further diluted in sodium chloride 0·9% or glucose 5% up to a maximum of 100mL.
• Ensure adequate flushing if patient is also prescribed a penicillin or cephalosporin, due to incompatibilty.

Compatibilities/incompatibilities

• Please refer to Medusa NHS Injectable Medicines Guide.

Monitoring/side effects

Renal function

• Prescribers should assess prior to prescribing and monitor whilst on treatment, and check child is passing urine. See link to Think Kidneys guidance below.
• Nephrotoxicity may be compounded by other agents eg amphotericin, cephalosporins, ciclosporin, indometacin, tacrolimus, vancomycin.

Auditory and vestibular function

• Prescribers should monitor for signs of ototoxicity and refer to audiology if it develops, or if gentamicin is continued for more than 7 days.
• Signs of ototoxicity include new tinnitus, dizziness, poor balance, hearing loss or oscillating vision.
• Stop gentamicin if ototoxicity occurs, and refer to microbiology or an infection specialist for advice on future therapy.
• Ototoxicity may be compounded by, eg, furosemide, and vancomycin. Monitor renal function and fluid balance closely.

NOTES

• Review the need for continuing treatment beyond 72 hours with a consultant microbiologist.

Contraindications

• Contra-indicated in patients with Myasthenia Gravis.
• Hypersensitivity to gentamicin or other ingredients.

Interactions

• Enhances the effects of non-depolarising muscle relaxants eg atracurium.

Licensed status

• Licensed.