gentamicin sulfate: clinical use

Prescribing considerations

• Reserve systemic treatment for susceptible infections where less toxic options are unsuitable, accounting for local microbiology and antimicrobial stewardship.
• Review renal function, hydration, age, body composition, infection site and organism susceptibility before and during treatment.
• Consider alternatives or genetic assessment where there is a known mitochondrial mutation or maternal history of aminoglycoside-associated deafness; urgent treatment should not be delayed solely for testing.
• Avoid prolonged topical use because sensitisation, superinfection and resistant organisms can emerge.

Contraindications and cautions

• Hypersensitivity to gentamicin, formulation excipients or other aminoglycosides, as specified by the product.
• Myasthenia gravis.
• Known or suspected perforated eardrum for the selected eye and ear drops.

Monitoring

• Serum gentamicin concentrations for systemic treatment, interpreted with timing of administration and local validated protocols.
• Renal function and urine output before and throughout systemic treatment, with continued review after exposure where clinically indicated.
• Auditory and vestibular function, particularly with pre-existing impairment, renal dysfunction, neonatal or older age, recurrent exposure or prolonged treatment.
• Electrolytes, hepatic parameters and blood count when clinically appropriate; review promptly if severe diarrhoea develops.

Clinical pharmacology

Gentamicin is a concentration-dependent bactericidal aminoglycoside that irreversibly disrupts bacterial protein synthesis at the 30S ribosomal subunit. It distributes mainly in extracellular fluid, undergoes little metabolism and is eliminated predominantly unchanged by glomerular filtration.

Formulation and product differences

• Selected products include concentrated solutions suitable for injection or dilution for infusion, a lower-strength paediatric injection, and a ready-to-use intravenous infusion.
• The ready-to-use infusion formulation is for intravenous infusion only and is not suitable for intramuscular administration.
• The selected injectable formulations differ in excipients, sodium content, compatibility, storage and permitted administration routes.
• The eye and ear drops contain benzalkonium chloride and are for ocular or auricular use only; they must not contact a perforated eardrum.

Solution for infusion

Route: Intravenous

Strengths: 1 mg/mL, 3 mg/mL

Ear drops

Route: Otic

Strengths: 0.3%, 0.3% w/v