Gentamicin

How it works

It binds irreversibly to the bacterial 30S ribosomal subunit, causing misreading of mRNA and inhibition of protein synthesis, producing concentration-dependent bactericidal activity.

Prescribing in practice

• Dose-related nephrotoxicity and irreversible ototoxicity (cochlear and vestibular) are the defining hazards, so therapy should be kept as short as possible with dosing and levels carefully managed, especially in renal impairment and the elderly.
• Doses are calculated and adjusted using therapeutic drug monitoring against local protocols, often using ideal body weight in obesity.
• Avoid concurrent nephrotoxic or ototoxic agents where possible, and use with particular caution in patients with myasthenia gravis.

Monitoring

Monitor serum gentamicin concentrations and renal function throughout treatment, with audiometry considered for prolonged courses.

Counselling the patient

• Report any hearing loss, ringing in the ears, dizziness or unsteadiness immediately.
• Regular blood tests are needed to keep the dose in the safe range.
• Tell the team if you have kidney problems or any balance or hearing difficulties.

Evidence & guidelines

Gentamicin dosing and therapeutic drug monitoring are governed by national and local antimicrobial protocols to balance efficacy against nephrotoxicity and ototoxicity.