Gentamicin

Gentamicin injection is used to prevent or treat a wide variety of bacterial infections. Gentamicin belongs to a class of drugs known as aminoglycoside antibiotics. It works by stopping the growth of bacteria.

Dosages of Gentamicin

Adult and Pediatric Dosage Forms and Strengths

Injectable solution

• 10 mg/ml
• 40 mg/ml

Dosage Considerations – Should be Given as Follows:

Susceptible Infections

Adult

Conventional dosing

• 3-5 mg/kg/day intravenously/intramuscularly (IV/IM) divided every 8 hours

Extended dosing interval (every 24 hours or more)

• Initial: 4-7 mg/kg/dose IV once/day
• Base dose on lean body weight
• Subsequent doses: Consult pharmacist

Pediatric

• Children 5 years and older: 2-2.5 mg/kg/dose intravenously/intramuscularly (IV/IM) every 8 hours
• Children under 5 years: 2.5 mg/kg/dose IV/IM every 8 hours

Infants under 30 weeks' gestation

• 0-28 days: 2.5 mg/kg/day IV/IM
• More than 28 days: 3 mg/kg/day IV/IM

Infants 30-36 weeks' gestation

• 0-14 days: 3 mg/kg/day IV/IM
• More than 14 days: 5 mg/kg/day IV/IM divided every 12 hours

Infants over 36 weeks' gestation

• 0-7 days: 5 mg/kg/day IV/IM divided every 12 hours
• More than 7 days: 7.5 mg/kg/day IV/IM divided every 8 hours

Surgical Infection

Prophylaxis

• Oral/pharyngeal: 1.5 mg/kg intravenously (IV) PLUS clindamycin 600-900 mg IV
• Ruptured viscus: 1.5 mg/kg IV every 8 hours PLUS clindamycin 600 mg IV every 6 hours

Endocarditis

Prophylaxis

Gastrointestinal (GI), genitourinary (GU) procedure:

• 1.5 mg/kg intravenously/intramuscularly (IV/IM) less than 30 minutes before procedure PLUS ampicillin or vancomycin

Cystic Fibrosis

• 7.5-10.5 mg/kg/day intravenously/intramuscularly (IV/IM) divided every 8 hours

Pelvic Inflammatory Disease (Off-label)

• Loading dose: 2 mg/kg intravenously or intramuscularly (IV or IM)
• Maintenance dose: 1.5 mg/kg IV or IM every 8 hours

Dosing Considerations

• Gentamicin may be given intravenously/intramuscularly (IV/IM)
• Dosing regimens are numerous and are adjusted based on CrCl and changes in the volume of distribution, as well as on the body space where the distribution of the agent will occur
• Monitor peak (4-12 mg/L) and trough (1-2 mg/L)
• Monitor renal and auditory function
• Each regimen must be followed by at least trough level drawn on a third or fourth dose, 30 minutes before dosing
• May draw peak level 30 minutes after a 30-minute infusion
• Use ideal body weight for mg/kg/dose; more accurate than total body weight
• Gentamicin is usually the first-line aminoglycoside against infections with gram-negative organisms such as Pseudomonas aeruginosa, Proteus, Escherichia coli, Klebsiella, Enterobacter, Serratia, and Citrobacter, as well as against Staphylococcus (gram-positive)

Dosing Modifications

Renal impairment

• CrCl greater than 90 mL/min and under 60 years: every 8 hours CrCl 60-90 mL/min or 60 years or older: every 12 hours CrCl 25-60 mL/min: every 24 hours CrCl 10-25 mL/min: every 48 hours CrCl less than 10 mL/min: every 72 hours
• Following dialysis in end-stage renal disease (ESRD)

Common side effects of gentamicin include:

• Neurotoxicity (spinning sensation [vertigo], loss of control of bodily movements)
• Gait instability
• Ototoxicity (auditory, vestibular)
• Kidney damage (decreased CrCl)
• Kidney damage if trough greater than 2 mg/L
• Swelling (edema)
• Rash
• Itching
• Stomach upset
• Injection site reactions (pain, irritation, and redness)

Less common side effects of gentamicin include:

• Drowsiness
• Headache
• Pseudomotor cerebri
• Photosensitivity
• Allergic reaction
• Skin redness
• Loss of appetite
• Nausea/vomiting
• Weight loss
• Increased salivation
• Enterocolitis
• Granulocytopenia
• Agranulocytosis
• Low platelet counts (thrombocytopenia)
• Elevated liver function tests (LFTs)
• Burning
• Stinging
• Tremors
• Muscle cramps
• Weakness
• Shortness of breath

Serious side effects of gentamicin include:

• Ringing or roaring sounds in the ear
• Hearing loss
• Dizziness
• An unusual decrease in the amount of urine while using gentamicin injection (pediatric)

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Gentamicin has no known severe interactions with other drugs.
• Gentamicin has serious interactions with at least 26 different drugs.
• Gentamicin has moderate interactions with at least 163 different drugs.
• Gentamicin has mild interactions with at 76 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

Warnings

Patients with dementia-related psychosis who are treated with antipsychotic drugs are at increased risk for death, as shown in short-term controlled trials; deaths in these trials appeared to be either cardiovascular (e.g., heart failure, sudden death) or infectious (e.g., pneumonia) in nature.

This drug is not approved for the treatment of patients with dementia-related psychosis.

This medication contains gentamicin. Do not take Modecate, Modecate Concentrate, Moditen, Prolixin, or RhoGentamicin if you are allergic to gentamicin or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

Neurotoxicity manifested as bilateral auditory and vestibular ototoxicity, can occur in patients with preexisting renal damage and in patients with normal renal function treated at higher doses and/or for periods longer than those recommended; high-frequency deafness usually occurs first and can be detected only with audiometric testing.

Aminoglycosides are potentially nephrotoxic; risk is greater in patients with impaired renal function and in those who receive high doses or prolonged therapy; rarely, nephrotoxicity may not become apparent until the first few days after cessation of therapy.

Use with caution in premature infants and neonates because of renal immaturity and the resulting prolongation of serum half-life of the drug.

Neuromuscular blockade and respiratory paralysis have been reported following parenteral injection, topical instillation (as in orthopedic and abdominal irrigation or in local treatment of empyema), and oral use of aminoglycosides, especially when given soon after anesthesia or muscle relaxants; if a blockage occurs, calcium salts may reverse these phenomena, but mechanical respiratory assistance may be necessary.

Avoid concurrent or sequential use of neurotoxic and/or nephrotoxic drugs, including other aminoglycosides (e.g., amikacin, streptomycin, neomycin, kanamycin, paromomycin).

Cumulative listing of drugs to avoid from all aminoglycoside package inserts includes amphotericin B, bacitracin, cephaloridine, cisplatin, colistin, polymyxin B, vancomycin, and viomycin.

Avoid potent diuretics (e.g., ethacrynic acid, furosemide) because they increase the risk of ototoxicity; when administered intravenously, diuretics may enhance aminoglycoside toxicity by altering antibiotic concentrations in serum and tissue.

This medication contains gentamicin. Do not take gentamicin if you are allergic to gentamicin or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

• Prior aminoglycoside toxicity or hypersensitivity

Effects of Drug Abuse

• No information available

Short-Term Effects

• See "What Are Side Effects Associated with Using Gentamicin?"

Long-Term Effects

• See "What Are Side Effects Associated with Using Gentamicin?"

Cautions

Risk of ototoxicity, neurotoxicity, nephrotoxicity.

Narrow therapeutic index (not intended for long-term therapy).

Caution in renal failure (not on dialysis), myasthenia gravis, hypocalcemia, and conditions that depress neuromuscular transmission.

Adjust dose in renal impairment.

Endocarditis prophylaxis (GI, GU procedure): American Heart Association (AHA) Guidelines recommend only for high-risk patients.

Pregnancy and Lactation

Use gentamicin during pregnancy only in LIFE-THREATENING emergencies when no safer drug is available. There is positive evidence of human fetal risk.

Gentamicin enters breast milk; use with caution if breastfeeding. The American Academy of Pediatrics (AAP) Committee states gentamicin is "compatible with nursing."