Gentamicin

GARAMYCIN

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Pronunciation: jen-ta-MYE-sin

Gentamicin ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Gentamicin ballicule

What it isAminoglycoside inhibiting the 30S ribosome; serious Gram-negative infection and combination therapy for endocarditis.

Why this oneAmong aminoglycosides, it is the standard partner for Gram-positive endocarditis synergy.

What limits itMonitor levels and renal function: nephrotoxicity is often reversible, but vestibular or auditory damage may not be.

Gentamicin molecular structure (skeletal formula) — Molecular structure: Gentamicin

FDA-approved for

Gram-negative infections (1971)

FDA label

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BOXED WARNING Nephrotoxicity and neurotoxicity (ototoxicity — vestibular and auditory, often irreversible); greater risk with renal impairment, high/prolonged dosing; monitor renal and eighth-nerve function

FDA dosing	Population	Start	Target	Max
Serious bacterial infection	Adults, normal renal function	3 mg/kg/day divided q8h	3 mg/kg/day q8h	5 mg/kg/day (life-threatening; 3–4 divided doses)
Serious bacterial infection	Children	6–7.5 mg/kg/day (2–2.5 mg/kg q8h)
Serious bacterial infection	Infants/neonates	7.5 mg/kg/day (2.5 mg/kg q8h)
Serious bacterial infection	Neonates ≤1 wk / premature	5 mg/kg/day (2.5 mg/kg q12h)

Renal Reduce dose or extend dosing interval in renal impairment; monitor peak and trough serum levels

Hepatic Undefined

Instructions

Give IM or by IV infusion
Dose on lean body mass in obesity
Monitor peak (4–6 mcg/mL) and trough (<2 mcg/mL); avoid prolonged peaks >12 mcg/mL
Usual duration 7–10 days

Available strengths

drops 0.3 %
inj 1.2, 1.6, 2, 10, 40 mg/mL
sol 3 mg/mL
cream 0.1 %
ointment 0.1, 0.3 %

Contraindications

History of hypersensitivity or serious toxic reaction to other aminoglycosides (cross-sensitivity)

Cautions

Nephrotoxicity — casts/proteinuria, rising BUN/creatinine
Neurotoxicity — ototoxicity (vestibular/auditory, may be irreversible)
Peripheral neuropathy/encephalopathy, neuromuscular effects
Higher risk with renal impairment, dehydration, prior ototoxic exposure

Adverse reactions

Nephrotoxicity
Ototoxicity (dizziness, vertigo, tinnitus, hearing loss)
Peripheral neuropathy
Rash/urticaria
Nausea/vomiting

Pregnancy Aminoglycosides can cause fetal harm (see Warnings)

Lactation Undefined

Cost

Gentamicin (GARAMYCIN)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $/unit	CostPlus
0.3 %	drops	per unit		not offered
1.2 mg/mL	inj	per unit		not offered
1.6 mg/mL	inj	per unit		not offered
2 mg/mL	inj	per unit		not offered
10 mg/mL	inj	per unit		not offered
40 mg/mL	inj	per unit	$1.30/mL	not offered

Generic entryPre-1982

⚠ BOXED WARNINGS

Nephrotoxicity and ototoxicity
Neuromuscular blockade

Classes and tags

Clinical profile

Therapeutic safety burden3 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryD

Defining liabilityNephrotoxicity and often irreversible ototoxicity require renal and concentration monitoring.

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