Gentamicin Oral Formulation Availability
Gentamicin is not available in an oral formulation for systemic infections and must be administered exclusively via intravenous (IV) or intramuscular (IM) routes. 1
Why Oral Gentamicin Is Not Used
- Gentamicin has extremely poor oral bioavailability, making it clinically useless for treating systemic infections when given by mouth 1
- The drug is not absorbed from the gastrointestinal tract in therapeutically meaningful amounts 2
- All major clinical guidelines from the American Heart Association, American College of Cardiology, and European Society of Cardiology specify only IV or IM administration for gentamicin in treating endocarditis, staphylococcal infections, and gram-negative bacterial infections 3, 1
Standard Routes of Administration
- Intravenous (IV): The preferred route for hospitalized patients, allowing for precise dosing and rapid therapeutic effect 3
- Intramuscular (IM): An acceptable alternative when IV access is difficult, with peak serum concentrations appearing 30-90 minutes after injection 2
- Standard dosing is 3 mg/kg/day IV or IM in 2-3 divided doses for most systemic infections 3
Failed Attempts at Alternative Routes
- A 2020 preclinical study investigated rectal administration of gentamicin (liquid enema and suppository formulations) in neonatal minipigs, but no gentamicin was detected in sera samples, providing no evidence to support therapeutic feasibility of rectal absorption 4
- This research was motivated by the need for simplified antibiotic delivery in low-resource settings, but the rectal route proved ineffective 4
Clinical Implications
- Any prescription for "oral gentamicin" for systemic infection represents a medication error and should be corrected immediately 1
- Therapeutic drug monitoring is essential when gentamicin is used, targeting trough concentrations <1 mg/L to minimize nephrotoxicity and ototoxicity 1
- Peak serum concentrations should reach 3-4 μg/mL (divided doses) or 10-12 μg/mL (once-daily dosing) to ensure efficacy 1