What It Is

Gentamicin is an aminoglycoside antibiotic used to treat a variety of bacterial infections. It is derived from the bacterium Micromonospora purpurea and is effective against a wide range of Gram-negative bacteria and some Gram-positive bacteria. Gentamicin is particularly valuable in treating severe infections where other antibiotics might not be effective.

Dosage Forms and Strengths

Gentamicin is available in several dosage forms, including:

• Injection: The most common form, available in vials for intravenous (IV) or intramuscular (IM) administration.
• Topical: Gentamicin is also available as an ointment or cream for topical application to the skin or eyes.
• Eye Drops: Used for ocular infections, available in sterile solutions.

Strengths vary based on the form and manufacturer, but typical concentrations include:

• Injection: 20 mg/mL, 40 mg/mL
• Topical Ointment: 0.1% (1 mg/g)
• Eye Drops: 0.3% solution (3 mg/mL)

Brand and Generic Names

Gentamicin is marketed under several brand names, including:

• Garamycin
• Genoptic (for eye drops)
• Gentak (for eye drops)

The generic name for this medication is simply "Gentamicin."

Indications for Use

Gentamicin is indicated for the treatment of severe infections caused by susceptible bacteria, including:

• Urinary Tract Infections: Particularly those caused by Gram-negative organisms.
• Respiratory Tract Infections: Including pneumonia and bronchitis.
• Abdominal Infections: Such as peritonitis or infections resulting from surgery.
• Skin Infections: Infections where topical gentamicin is applied.
• Ocular Infections: Conjunctivitis and keratitis when treated with eye drops.

It is often used in combination with other antibiotics to enhance its effectiveness and broaden its spectrum of action.

Mechanism of Action

Gentamicin works by inhibiting bacterial protein synthesis. It binds to the 30S ribosomal subunit of bacteria, leading to the misreading of mRNA. This results in the production of non-functional or toxic proteins, disrupting essential bacterial processes and ultimately leading to bacterial cell death. Gentamicin's action is bactericidal, meaning it kills bacteria rather than merely inhibiting their growth.

Administration and Dosage

The dosage of gentamicin depends on the type and severity of the infection, as well as the patient's age, weight, and kidney function. General guidelines include:

• Injection (IV or IM): For adults, doses typically range from 3 to 5 mg/kg/day, divided into two to three doses. For severe infections, higher doses may be used, and dosing adjustments are often required based on serum levels and renal function.
• Topical: Apply a thin layer to the affected area 1 to 3 times daily.
• Eye Drops: Usually, 1-2 drops are applied every 4-6 hours, depending on the severity of the infection.

Effects and Precautions

Side Effects:

• Nephrotoxicity: Gentamicin can cause kidney damage, especially with prolonged use or high doses. Regular monitoring of kidney function is recommended.
• Ototoxicity: It may lead to hearing loss or balance issues, as it can affect the inner ear.
• Neuromuscular Blockade: Rarely, it can cause neuromuscular paralysis or weakness.
• Allergic Reactions: Some patients may experience rash, itching, or swelling.

Precautions:

• Renal Function: Monitor renal function closely in patients with pre-existing kidney conditions.
• Hearing: Regular audiometric testing is advised for patients receiving long-term therapy.
• Drug Interactions: Gentamicin may interact with other nephrotoxic or ototoxic drugs, requiring careful management.

Conclusion

Gentamicin remains a potent and valuable antibiotic in the treatment of serious bacterial infections. Its effectiveness against a broad range of pathogens, combined with its specific mechanisms of action, makes it a critical component of many antimicrobial treatment regimens. However, its potential for severe side effects necessitates careful monitoring and dosage adjustment, particularly in vulnerable populations. By understanding its uses, mechanisms, and precautions, healthcare providers can maximize its therapeutic benefits while minimizing risks to patients.