Aminoglycosides Explained: Gentamicin, Amikacin & Tobramycin Guide for Severe Infections

Aminoglycosides, like Gentamicin and Amikacin, are strong antibiotics for serious Gram-negative infections. Here’s a look at their mechanism, spectrum, uses, side effects, and monitoring needs.

Introduction

Aminoglycosides are bactericidal antibiotics that stop protein synthesis. They treat serious Gram-negative infections. They often use them with beta-lactams to boost effectiveness. Common examples include Gentamicin, Amikacin, and Tobramycin.

Medications in the Class

• Gentamicin (prototype)

• Amikacin

• Tobramycin

• Neomycin is primarily used in topical or oral forms for bowel cleaning.

• Streptomycin (historical, used in TB and plague)

Mechanism of Action

Aminoglycosides attach to the 30S ribosomal subunit. This leads to misreading of mRNA and blocks bacterial protein synthesis. They are bactericidal and depend on concentration for effectiveness.

Spectrum of Activity

• Gram-negative aerobic bacteria: E. coli, Klebsiella, Pseudomonas, Proteus, Enterobacter

• Synergy against Gram-positive bacteria: Streptococcus and Staphylococcus (with beta-lactams or vancomycin)

• Not effective against anaerobes (need oxygen to enter)

• Resistant organisms: MRSA, VRE (not effective alone)

  Watch the video about it aminoglycoside.

  
  

Indications (When Used)

• Severe Gram-negative infections: bacteremia, sepsis, pneumonia, complicated UTIs

• Endocarditis (used with beta-lactams)

• Intra-abdominal infections (in combination)

• Tuberculosis (Streptomycin for MDR-TB)

• Nosocomial infections from Pseudomonas

Contraindications (When Not to Use)

• Known allergy to aminoglycosides

• Pre-existing renal impairment (risk of kidney damage)

• Myasthenia gravis (risk of muscle issues)

• Pregnancy (risk of fetal hearing loss)

Side Effects

• Nephrotoxicity: acute kidney injury

• Ototoxicity: potential ear damage, permanent

• Rare neuromuscular blockade

• Allergic reactions (rash, fever)

Drug Interactions

• Loop diuretics (e.g., furosemide): higher risk of ear damage

• Vancomycin or Amphotericin B: increases kidney damage risk

• Muscle relaxants: may worsen muscle issues

• Cephalosporins and Penicillins: can work together but don’t mix in the same IV solution

Antidote

• No specific antidote for overdose

• Nephrotoxicity: supportive care, hydration, and monitoring

• Ototoxicity: stop use immediately

• Neuromuscular blockade: treated with calcium gluconate and supportive care

Monitoring of Potential Complications

• Renal function: check serum creatinine, BUN, and urine output

• Serum drug levels: monitor peak and trough levels to avoid toxicity

• Hearing and balance: check before and during long-term use

• Electrolytes: monitor potassium and magnesium levels

Aminoglycosides are potent antibiotics for severe Gram-negative infections. Their careful use is essential due to risks like nephrotoxicity and ototoxicity. They are vital for treating infections that resist multiple drugs. They also help in combined therapy for Gram-positive cases.