Gentamicin is a bactericidal aminoglycoside antibiotic derived from Micromonospora purpurea. It is a broad-spectrum antibiotic primarily effective against aerobic Gram-negative bacilli, including Pseudomonas aeruginosa, and some Gram-positive organisms like Staphylococcus aureus. In the Indian context, it is a critical, cost-effective agent for severe infections, but its use is tempered by the risk of nephrotoxicity and ototoxicity, necessitating therapeutic drug monitoring (TDM) where available.
Adult: Conventional: 3-5 mg/kg/day in 2-3 divided doses (e.g., 80mg every 8 hours). Extended-Interval (Once-Daily Dosing - ODD): 5-7 mg/kg as a single daily dose. ODD is preferred for most systemic infections in patients with normal renal function due to better efficacy and potentially lower toxicity.
Note: For IV use: Dilute 80mg in 50-100 mL of compatible IV fluid (NS or D5W). Infuse over 30-60 minutes. NEVER give as IV bolus (risk of neuromuscular blockade). For IM use: Administer by deep intramuscular injection into a large muscle mass. Ensure patient is well-hydrated to maintain renal perfusion.
Gentamicin binds irreversibly to the bacterial 30S ribosomal subunit, specifically to the 16S rRNA and certain ribosomal proteins. This binding interferes with the initiation complex, misreads the mRNA code, and causes premature termination of protein synthesis. The primary effect is bactericidal due to the production of aberrant, non-functional proteins and disruption of the bacterial cell membrane.
Pregnancy: Category D (US FDA). Aminoglycosides cross the placenta. Risk of fetal ototoxicity (8th cranial nerve damage) exists. Use only if the potential benefit justifies the potential risk to the fetus, typically for life-threatening infections where safer alternatives cannot be used.
Driving: Patients experiencing vertigo, dizziness, or tinnitus as side effects should be advised NOT to drive or operate heavy machinery until symptoms resolve.
| Furosemide/Ethacrynic acid | Potentiates ototoxicity (additive damage to cochlea) | Major |
| Other Nephrotoxins (Vancomycin, Amphotericin B, Cisplatin, NSAIDs, Cyclosporine) | Increased risk of acute kidney injury | Major |
| Neuromuscular Blocking Agents (Succinylcholine, Tubocurarine) | Potentiates neuromuscular blockade, risk of prolonged apnea/respiratory arrest | Major |
| Penicillins (especially high-dose) in vitro | Chemical inactivation if mixed in the same IV line/bag. Administer separately. | Moderate |
| Indomethacin in neonates | May increase gentamicin levels and toxicity risk | Moderate |
| Cephalosporins (some) | Theoretical increased nephrotoxicity; clinical significance debated | Moderate |