Drug Guide

Generic Name

Gentamicin Sulfate

Brand Names Garamycin, U-gencin, Bristagen, Apogen, Gentamicin, Gentamicin Sulfate In Sodium Chloride 0.9% In Plastic Container, Gentafair, Genoptic, Gentacidin, Gentak

Classification

Therapeutic: Antibiotic, Aminoglycoside

Pharmacological: Bactericidal via inhibition of protein synthesis

FDA Approved Indications

Treatment of various bacterial infections caused by susceptible organisms, including urinary tract infections, respiratory infections, intra-abdominal infections, and skin infections.

Mechanism of Action

Gentamicin binds to 30S ribosomal subunit, inhibiting bacterial protein synthesis, leading to bactericidal activity.

Dosage and Administration

Adult: Dose varies based on infection and organism susceptibility; typically 3-5 mg/kg/day divided into multiple doses.

Pediatric: Dose varies; usually 2.5-3 mg/kg every 8 hours, adjusted based on renal function.

Geriatric: Use with caution; monitor renal function and drug levels.

Renal Impairment: Dose adjustment needed; monitor serum levels.

Hepatic Impairment: No specific adjustment required.

Pharmacokinetics

Absorption: Poor oral absorption; given IV, IM, topical, or ophthalmic.

Distribution: Widely distributed in body tissues and fluids, including cerebrospinal fluid (CSF) when meninges are inflamed.

Metabolism: Not metabolized.

Excretion: Primarily excreted unchanged in urine.

Half Life: 2-3 hours in patients with normal renal function.

Contraindications

Hypersensitivity to gentamicin or other aminoglycosides.

Precautions

Renal impairment, hearing loss, neuromuscular weakness, dehydration, and in cases of concurrent ototoxic or nephrotoxic drugs. Use with caution during pregnancy and lactation.

Adverse Reactions - Common

Nephrotoxicity (Uncommon)
Ototoxicity (auditory and vestibular) (Uncommon)
Neuromuscular blockade (Rare)
Infusion site reactions (Common)

Adverse Reactions - Serious

Chronic kidney disease or reversible renal failure (Less common)
Hearing loss, potentially permanent (Less common)
Respiratory paralysis in cases of neuromuscular blockade (Rare)

Drug-Drug Interactions

Other nephrotoxic drugs (e.g., cisplatin, amphotericin B)
Loop diuretics (e.g., furosemide)
Muscle relaxants

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor renal function (BUN, creatinine), serum drug levels, hearing assessment, and neuro status.

Diagnoses:

Risk for nephrotoxicity
Risk for ototoxicity
Risk for neuromuscular impairment

Implementation: Administer IV or IM as prescribed; monitor serum gentamicin levels (peak and trough); ensure adequate hydration; assess for signs of ototoxicity and nephrotoxicity.

Evaluation: Evaluate clinical response, monitor laboratory parameters, and adjust dosing accordingly.

Patient/Family Teaching

Complete full course of therapy.
Report signs of hearing loss, tinnitus, dizziness, or imbalance.
Report difficulty urinating or signs of kidney issues.
Use ototoxic drugs cautiously and avoid concurrent use without physician approval.

Special Considerations

Black Box Warnings:

Nephrotoxicity and ototoxicity risk increased with high doses or prolonged therapy.
Use cautiously in patients with impaired renal function.

Genetic Factors: Genetic predisposition may influence susceptibility to ototoxicity.

Lab Test Interference: Potential interference with certain creatinine assays.

Overdose Management

Signs/Symptoms: Ototoxicity (hearing loss, tinnitus), nephrotoxicity, neuromuscular blockade leading to paralysis.

Treatment: Discontinue gentamicin, provide supportive care, and consider dialysis if severe.

Storage and Handling

Storage: Store at room temperature, protected from light.

Stability: Stable until expiration date if unopened and stored properly.