gentamicin

Action and Spectrum

Actions and spectrum: 

gentamicin belongs to the class of aminoglycosides. It is effective against gram-negative bacteria, including Pseudomonas aeruginosa, Proteus spp., Escherichia coli, Klebsiella pneumoniae, and Enterobacter spp. gentamicin binds to the 30S ribosomal subunit of bacteria, thereby inhibiting protein synthesis and leading to cell death. It is primarily bactericidal, meaning that it kills bacteria rather than merely inhibiting their growth. 

gentamicin is also active against some gram-positive bacteria, such as Staphylococcus aureus and Streptococcus pyogenes. However, its use in these infections is limited due to the emergence of resistant strains. gentamicin is not effective against anaerobic bacteria, viruses, or fungi. 

Drug Interaction

Adverse Reaction

Frequency defined

>10%

Gait instability

Nephrotoxicity

Neurotoxicity

Ototoxicity

1-10%

Rash

Itching

Edema

Skin redness

<1%

Headache

Photosensitivity

Erythema

Nausea/vomiting

Increased salivation

Granulocytopenia

Thrombocytopenia

Burning

Tremors

Weakness
Drowsiness

Pseudomotor cerebri

Allergic reaction

Anorexia

Weight loss

Enterocolitis

Agranulocytosis

Elevated LFTs

Stinging

Muscle cramps

Dyspnea

Black Box Warning

Gentamicin drug leads to severe and irreversible hearing loss and damage to kidney.

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

• Hypersensitivity to gentamicin or any component of the formulation 
• Pre-existing renal insufficiency 
• Myasthenia gravis 
• Parkinsonism 
• Infants and neonates up to 1 month of age 
• Pregnancy until the benefits outweigh the risks to the fetus 
• Lactation, as gentamicin is excreted in human milk.

Caution: 

• Kidney problems: gentamicin can cause kidney damage or worsen pre-existing kidney problems. Thus, it should be used under caution in patients with kidney problems. Patients with impaired kidney function may require dosage adjustments or more frequent monitoring of kidney function. 
• Neurotoxicity: gentamicin can cause damage to the nervous system, resulting in symptoms such as vertigo, tinnitus, hearing loss, and muscular weakness. Patients with pre-existing neuromuscular disorders, such as myasthenia gravis, are at an increased risk of experiencing these side effects. 
• Allergies: gentamicin should not be used in patients with a history of allergic reactions to aminoglycosides, as it may cause severe allergic reactions. 
• Pregnancy and breastfeeding: gentamicin is classified as a pregnancy category D medication, which means it may cause harm to the unborn baby. 
• Pre-existing medical conditions: gentamicin should be used with caution in patients with pre-existing medical conditions such as hearing loss, kidney disease, and neuromuscular disorders. 
• Other medications: gentamicin may interact with other medications, such as diuretics, muscle relaxants, and other antibiotics, leading to increased risk of side effects.

Comorbidities: 

• Renal impairment: gentamicin is eliminated by the kidneys, so it can accumulate in patients with renal impairment, leading to increased risk of toxicity. Dosing adjustments and careful monitoring of kidney function are required in patients with renal impairment. 
• Neuromuscular disorders: gentamicin can have neuromuscular blocking effects and exacerbate muscle weakness in patients with neuromuscular disorders such as myasthenia gravis. 
• Hearing impairment: gentamicin can cause irreversible hearing loss, especially in patients with pre-existing hearing impairment or exposure to loud noise. 
• Pregnancy: gentamicin is considered safe to use during pregnancy, but it should be used with caution as with any medication during pregnancy. 
• Breastfeeding: gentamicin is excreted in breast milk and can be harmful to nursing infants, so caution is advised when administering gentamicin to lactating mothers. 
• Liver impairment: gentamicin is not primarily metabolized by the liver, but its use should be monitored in patients with liver impairment due to its potential for nephrotoxicity. 
• Dehydration: gentamicin can cause kidney damage and dehydration can exacerbate this effect. Therefore, patients receiving gentamicin should maintain adequate hydration. 

Pregnancy / Lactation

Pregnancy consideration: US FDA pregnancy category: D 

Lactation: gentamicin is excreted in human milk  

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: There is no evidence of risk to the fetus found in animal reproduction studies and there are not enough studies on pregnant women. 
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for an effect in humans, care must be taken for potential risks in pregnant women. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms, but despite potential risks may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits These category drugs should be prohibited for pregnant women. 
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

gentamicin is an aminoglycoside antibiotic that works by binding to the bacterial 30S ribosomal subunit, thereby inhibiting protein synthesis. It is bactericidal rather than just inhibiting their growth. 

gentamicin has a broad spectrum of activity, with activity against both Gram-positive and Gram-negative bacteria. It is particularly effective against Pseudomonas aeruginosa, Enterobacteriaceae, and other aerobic Gram-negative bacteria.  

Pharmacodynamics: 

gentamicin shows bactericidal activity and binds to the 30S ribosomal subunit of susceptible bacteria, which interferes with protein synthesis, leading to the production of abnormal and nonfunctional proteins. This leads to cell death. gentamicin has a broad-spectrum activity against both gram-negative and some gram-positive bacteria, including Enterobacteriaceae, Pseudomonas aeruginosa, Proteus spp., and Staphylococcus spp.  

Pharmacokinetics: 

Absorption 

gentamicin is not absorbed orally and must be given parenterally. 

Distribution 

gentamicin has a large volume of distribution, which allows it to distribute throughout the extracellular fluid. It can cross the placenta and is excreted in breast milk. 

Metabolism 

gentamicin is not metabolized by the body. 

Elimination and excretion 

gentamicin is eliminated primarily unchanged by the kidneys through glomerular filtration. In impaired renal function, the elimination of gentamicin may be slowed, leading to increased serum levels and a risk of toxicity. 

Adminstartion

The route of administration depends on indication and severity of the infection.

If gentamicin is taken orally, it is not absorbed by gastrointestinal tract. It is not used in systemic infections. It is used in the topical form to treat intestinal infections which are caused by bacteria.

Gentamicin is used by intravenously or intramuscularly to treat systemic infections which are caused by susceptible bacteria. The duration ad frequency of dosage to treat the disease is dependent on different factors like weight, age, renal function, and severity of infection.

It is administered for every day to treat severe infection in adults. Multiple dosage form is also necessary in certain cases like newborns and patients who have compromised function of kidney.

Patient Information Leaflet

Generic Name: gentamicin 

Pronounced: [ GEN-ta-MYE-sin]  

Why do we use gentamicin? 

• Urinary tract infections: gentamicin may be used to treat UTI caused by certain bacteria, such as E. coli. 
• Respiratory tract infections: gentamicin may be used to treat respiratory tract infections caused by certain bacteria, such as Pseudomonas aeruginosa. 
• Skin and Bone infections: gentamicin can be used to treat bone and skin infections caused by certain bacteria, such as Staphylococcus aureus. 
• Bloodstream infections: gentamicin may be used in combination with other antibiotics to treat bloodstream infections caused by certain bacteria, such as Enterobacter species. 
• Eye infections: gentamicin may be used to treat eye infections caused by certain bacteria, such as Pseudomonas aeruginosa.