Which Drug is Considered an Aminoglycoside? Key Examples and Clinical Uses

October 6, 2025 •

4 min read

The first aminoglycoside, streptomycin, was isolated from soil bacteria in 1943, marking a major milestone in antibacterial therapy. In the decades since, a number of other agents have been developed, raising the question: which drug is considered an aminoglycoside, and for what are they used?.

Quick Summary

Aminoglycosides are a class of antibiotics that includes drugs like gentamicin, amikacin, and tobramycin, used to treat severe bacterial infections by inhibiting bacterial protein synthesis. They are typically administered via injection due to poor oral absorption, carry a risk of ototoxicity and nephrotoxicity, and require careful monitoring.

Key Points

Gentamicin: A commonly used and cost-effective aminoglycoside for severe gram-negative infections.
Amikacin: Often reserved for infections resistant to other aminoglycosides due to its chemical structure.
Mechanism of Action: Aminoglycosides kill bacteria by binding to the 30S ribosomal subunit, inhibiting protein synthesis.
Major Side Effects: Significant risks include irreversible ototoxicity (hearing loss) and potentially reversible nephrotoxicity (kidney damage).
Administration: Typically administered via injection (IV or IM) due to poor oral absorption, though topical and inhaled forms exist.
Drug Resistance: Bacterial resistance often involves modifying enzymes, which new aminoglycosides like plazomicin are designed to overcome.
Clinical Uses: Employed for serious infections like sepsis, endocarditis, and chronic P. aeruginosa infections in cystic fibrosis.

What Are Aminoglycosides?

Aminoglycosides are a class of potent, bactericidal antibiotics primarily used for serious infections caused by aerobic, Gram-negative bacteria, such as Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae. They may also be used in combination with other antibiotics for certain Gram-positive infections like endocarditis. The first aminoglycoside, streptomycin, was discovered in the 1940s, and the class has since expanded.

These drugs feature a core structure of amino sugars linked to an aminocyclitol ring and target the bacterial ribosome, making them effective against susceptible organisms. Their use requires careful monitoring due to potential toxicity, and administration routes are specific.

Key Examples: Which Drug is Considered an Aminoglycoside?

Several well-known drugs fall under the aminoglycoside classification. These include:

Gentamicin: A widely used and cost-effective option for a range of gram-negative aerobic infections.
Amikacin: A semisynthetic aminoglycoside effective against bacteria resistant to other drugs in this class, such as gentamicin and tobramycin, due to its resistance to bacterial inactivating enzymes.
Tobramycin: Often preferred for its activity against P. aeruginosa, particularly in cystic fibrosis patients with lung infections. It is available in various forms, including inhalation.
Streptomycin: The initial aminoglycoside discovered, historically used for tuberculosis and still an option for certain zoonotic infections like plague and tularemia.
Neomycin: High toxicity limits systemic use; primarily found in topical formulations for skin infections and used orally for intestinal bacterial suppression.
Plazomicin: A newer agent designed to combat common resistance mechanisms in multidrug-resistant gram-negative pathogens.

How Aminoglycosides Work: Mechanism of Action

Aminoglycosides kill bacteria by disrupting protein synthesis. This process involves several steps:

Transport: Aminoglycosides are transported into the bacterial cell via an oxygen-dependent process, which is why they don't work against anaerobes.
Ribosomal Binding: Inside the cell, the drug binds irreversibly to the 30S ribosomal subunit.
Protein Synthesis Inhibition: This binding interferes with the translation of mRNA, halting the creation of functional proteins.
Codon Misreading: The interference causes misreading of mRNA, resulting in the production of faulty proteins.
Membrane Damage: These abnormal proteins can integrate into the bacterial cell membrane, increasing permeability and leading to further drug entry and cell death.

Therapeutic Uses and Applications

Aminoglycosides are used for specific clinical needs, including:

Severe Systemic Infections: Treating conditions like sepsis and bacteremia, often with a beta-lactam antibiotic.
Cystic Fibrosis: Inhaled tobramycin is used for chronic P. aeruginosa lung infections.
Tuberculosis: Streptomycin and amikacin are components of multidrug regimens for tuberculosis, including resistant forms.
Infective Endocarditis: Used synergistically with penicillins or cephalosporins for gram-positive endocarditis.
Topical Infections: Neomycin and gentamicin are used topically for eye, ear, and skin infections.
Preoperative Bowel Preparation: Oral neomycin is used to reduce intestinal bacteria before surgery.

Comparing Common Aminoglycosides


Feature	Gentamicin	Amikacin	Tobramycin
Spectrum of Activity	Broad, includes most gram-negative aerobes	Broad, with enhanced activity against bacteria resistant to other aminoglycosides	Broad, particularly potent against P. aeruginosa
Resistance Profile	Susceptible to several common resistance mechanisms	Less susceptible to many inactivating enzymes, making it effective against some resistant strains	Similar to gentamicin, but generally has superior activity against P. aeruginosa
Cost	Typically the lowest cost option	Often more expensive than gentamicin	Variable cost, can be more expensive depending on formulation
Primary Use	General-purpose use for severe gram-negative infections, often in combination therapy	Infections resistant to other aminoglycosides, severe nosocomial infections	Infections involving P. aeruginosa, such as in cystic fibrosis patients
Common Route	IV, IM, topical	IV, IM	IV, IM, inhaled, topical

Important Considerations and Adverse Effects

Aminoglycosides have a risk of significant toxicities, requiring careful monitoring.

Ototoxicity: Irreversible damage to the inner ear causing hearing loss or balance problems is a major concern. Genetic factors can play a role.

Nephrotoxicity: Kidney damage is common and usually reversible upon stopping the drug. It's linked to cumulative dose and treatment duration. Dehydration and other nephrotoxic drugs increase risk.

Neuromuscular Blockade: A less frequent but serious effect causing muscle weakness and respiratory issues, more likely at high doses or in patients with existing neuromuscular conditions.

Drug Interactions: Risk of adverse effects is increased with certain drugs like loop diuretics, other nephrotoxic agents, and neuromuscular blockers.

Conclusion

Several drugs are considered aminoglycosides, with gentamicin, amikacin, and tobramycin being prominent examples. They remain crucial for treating severe gram-negative infections, especially resistant ones, due to their unique mechanism of action. However, the risk of serious side effects like nephrotoxicity and ototoxicity necessitates careful patient selection, precise dosing, and close monitoring. Aminoglycosides are expected to retain their importance in medicine as antibiotic resistance continues to be a challenge.

Managing Aminoglycoside Toxicity

Strategies to mitigate the risk of toxicity include:

Monitoring Blood Levels: Measuring peak and trough drug concentrations ensures therapeutic levels while minimizing toxicity.
Extended-Interval Dosing: Giving a single, high daily dose may reduce nephrotoxicity risk compared to multiple doses.
Patient Hydration: Keeping patients well-hydrated helps protect the kidneys.
Minimizing Treatment Duration: Limiting therapy duration reduces cumulative toxicity.

These strategies, combined with assessing patient risk factors, are vital for safe and effective aminoglycoside use. For further details on aminoglycoside pharmacology and resistance, resources like the NIH's StatPearls provide comprehensive information.

Frequently Asked Questions

Yes, gentamicin is a well-known and commonly used drug that is considered an aminoglycoside antibiotic.

The most common and serious side effects of aminoglycosides are ototoxicity (inner ear damage, which can be irreversible) and nephrotoxicity (kidney damage, which is often reversible).

Aminoglycosides are bactericidal, meaning they kill bacteria by irreversibly binding to the 30S ribosomal subunit, which inhibits protein synthesis and leads to the production of faulty proteins that ultimately cause cell death.

Aminoglycosides are used to treat severe infections caused by aerobic, Gram-negative bacteria, including sepsis, meningitis, and infections in patients with cystic fibrosis.

These drugs are poorly absorbed when taken orally, so they are usually administered via intramuscular or intravenous injection to achieve therapeutic concentrations in the bloodstream.

Both are aminoglycosides, but amikacin is a semisynthetic variant that is more resistant to bacterial inactivating enzymes. This makes it particularly effective against infections that are resistant to gentamicin.

Yes, ototoxicity is a significant and potential adverse effect of aminoglycosides, which can lead to hearing loss. The risk increases with prolonged use and is a major factor limiting the duration of therapy.

Yes, some aminoglycosides, such as neomycin and gentamicin, are available in topical formulations for treating skin, eye, and ear infections.