Gentamicin Drug Profile

What is Gentamicin?

Gentamicin is an aminoglycoside antibiotic used to treat serious bacterial infections caused by gram-negative bacteria. It belongs to a class of antibiotics that work by disrupting bacterial protein synthesis, making it effective against many types of resistant bacteria. Gentamicin is typically reserved for severe infections due to its potential for serious side effects.

Uses

Gentamicin is prescribed for several serious bacterial infections:

• Sepsis and bloodstream infections: Used to treat life-threatening infections that have spread throughout the body
• Respiratory tract infections: Particularly pneumonia caused by gram-negative bacteria in hospitalized patients
• Urinary tract infections: Severe kidney infections (pyelonephritis) and complicated UTIs that don’t respond to other antibiotics
• Intra-abdominal infections: Infections within the abdomen, often used in combination with other antibiotics
• Skin and soft tissue infections: Severe wound infections, burns, or diabetic foot infections

How it works

Gentamicin works by binding to the 30S ribosomal subunit of bacteria, which disrupts their ability to make essential proteins. Without these proteins, bacteria cannot survive or reproduce, leading to their death. This mechanism is particularly effective against gram-negative bacteria, which are often resistant to other types of antibiotics.

Side effects

Common side effects:

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• Nausea and vomiting
• Loss of appetite
• Headache
• Dizziness
• Pain or irritation at injection site
• Rash or skin irritation
• Fatigue
• Muscle weakness

Serious side effects requiring immediate medical attention:

• Hearing loss or ringing in ears (ototoxicity)
• Kidney damage with decreased urination or swelling
• Severe allergic reactions with difficulty breathing
• Neuromuscular blockade causing muscle paralysis
• Severe diarrhea indicating antibiotic-associated colitis

Warnings and precautions

• Kidney function monitoring: Regular blood tests are essential as gentamicin can cause kidney damage, especially in elderly patients or those with existing kidney problems
• Hearing assessment: Audiometric testing may be needed during treatment as the drug can cause permanent hearing loss
• Pregnancy considerations: Gentamicin crosses the placenta and may cause eighth cranial nerve damage in the developing fetus; use only when benefits outweigh risks
• Neuromuscular conditions: Patients with myasthenia gravis or Parkinson’s disease should use with extreme caution due to risk of muscle weakness
• Dehydration risk: Adequate hydration must be maintained to reduce kidney toxicity risk

Interactions

• Loop diuretics (furosemide): Increased risk of hearing damage and kidney toxicity when used together
• Vancomycin: Combined use significantly increases nephrotoxicity risk
• Amphotericin B: Additive kidney damage potential requires careful monitoring
• Neuromuscular blocking agents: Enhanced muscle paralysis effects during surgery or procedures
• Warfarin: May enhance anticoagulant effects, requiring dose adjustments
• Digoxin: Gentamicin may increase digoxin levels, potentially causing toxicity
• Cisplatin: Increased risk of both kidney damage and hearing loss
• NSAIDs: May reduce kidney function and increase gentamicin toxicity risk

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Dosage

Gentamicin dosing is highly individualized and based on patient weight, kidney function, and infection severity. Typical adult doses range from 3-7 mg/kg/day, either given as a single daily dose or divided into multiple doses throughout the day. The drug is administered intravenously or intramuscularly in hospital settings. Blood levels are monitored regularly to ensure therapeutic effectiveness while avoiding toxicity. Dosage adjustments are necessary for patients with reduced kidney function, and treatment duration typically ranges from 7-10 days depending on the infection type and patient response.

Important: Gentamicin dosage must always be determined and monitored by a healthcare provider due to its narrow therapeutic window and potential for serious side effects.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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