Gentamicin

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Gentamicin
Black Box Warning
Adult Indications & Dosage
Pediatric Indications & Dosage
Contraindications
Warnings & Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Administration & Monitoring
Overdosage
Pharmacology
Clinical Studies
How Supplied
Images
Patient Counseling Information
Precautions with Alcohol
Brand Names
Look-Alike Names

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vignesh Ponnusamy, M.B.B.S. [2]

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Black Box Warning

See full prescribing information for complete Boxed Warning.
  • Patients treated with aminoglycosides should be under close clinical observation because of the potential toxicity associated with their use.
  • As with other aminoglycosides, gentamicin injection is potentially nephrotoxic. The risk of nephrotoxicity is greater in patients with impaired renal function and in those who receive high dosage of prolonged therapy.
  • Neurotoxicity manifested by ototoxicity, both vestibular and auditory, can occur in patients treated with gentamicin, primarily in those with pre-existing renal damage and in patients with normal renal function treated with higher doses and/or for longer periods than recommended. Aminoglycoside-induced ototoxicity is usually irreversible. Other manifestations of neurotoxicity may include numbness, skin tingling, muscle twitching and convulsions.
  • Renal and eighth cranial nerve function should be closely monitored, especially in patients with known or suspected reduced renal function at onset of therapy and also in those whose renal function is initially normal but who develop signs of renal dysfunction during therapy. Urine should be examined for decreased specific gravity, increased excretion of protein and the presence of cells or casts. Blood urea nitrogen (BUN), serum creatinine or creatinine clearance should be determined periodically. When feasible, it is recommended that serial audiograms be obtained in patients old enough to be tested, particularly high-risk patients. Evidence of ototoxicity (dizziness, vertigo, tinnitus, roaring in the ears or hearing loss) or nephrotoxicity requires dosage adjustment or discontinuance of the drug. As with the other aminoglycosides, on rare occasions changes in renal and eighth cranial nerve function may not become manifest until soon after completion of therapy.
  • Serum concentrations of aminoglycosides should be monitored when feasible to assure adequate levels and to avoid potentially toxic levels. When monitoring gentamicin peak concentrations, dosage should be adjusted so that prolonged levels above 12 mcg/mL are avoided. When monitoring gentamicin trough concentrations, dosage should be adjusted so that levels above 2 mcg/mL are avoided. Excessive peak and/or trough serum concentrations of aminoglycosides may increase the risk of renal and eighth cranial nerve toxicity.
  • In the event of overdosage or toxic reactions, hemodialysis may aid in the removal of gentamicin from the blood, especially if renal function is, or becomes, compromised. The rate of removal of gentamicin is considerably lower by peritoneal dialysis than it is by hemodialysis.
  • In the newborn infant, exchange transfusions may also be considered.
  • Concurrent and/or sequential systemic or topical use of other potentially neurotoxic and/or nephrotoxic drugs, such as cisplatin, cephaloridine, kanamycin, amikacin, neomycin, polymyxin B, colistin, paromomycin, streptomycin, tobramycin, vancomycin and viomycin, should be avoided. Other factors which may increase patient risk of toxicity are advanced age and dehydration.
  • The concurrent use of gentamicin with potent diuretics, such as ethacrynic acid or furosemide, should be avoided, since certain diuretics by themselves may cause ototoxicity. In addition, when administered intravenously, diuretics may enhance aminoglycoside toxicity by altering the antibiotic concentration in serum and tissue.
  • Aminoglycosides can cause fetal harm when administered to a pregnant woman.

Overview

Gentamicin is an aminoglycoside that is FDA approved for the {{{indicationType}}} of . There is a Black Box Warning for this drug as shown here. Common adverse reactions include .

Adult Indications and Dosage

FDA-Labeled Indications and Dosage (Adult)

Gentamicin Injection, USP is indicated in the treatment of serious infections caused by susceptible strains of the following microorganisms: Pseudomonas aeruginosa, Proteus species (indole-positive and indole-negative), Escherichia coli, Klebsiella-Enterobacter-Serratia species, Citrobacter species and Staphylococcus species (coagulase-positive and coagulase-negative).

Clinical studies have shown gentamicin injection to be effective in bacterial neonatal sepsis; bacterial septicemia and serious bacterial infections of the central nervous system (meningitis), urinary tract, respiratory tract, gastrointestinal tract (including peritonitis), skin, bone and soft tissue (including burns). Aminoglycosides, including gentamicin, are not indicated in uncomplicated initial episodes of urinary tract infections unless the causative organisms are susceptible to these antibiotics and are not susceptible to antibiotics having less potential for toxicity.

Specimens for bacterial culture should be obtained to isolate and identify causative organisms and to determine their susceptibility to gentamicin.

Gentamicin injection may be considered as initial therapy in suspected or confirmed gram-negative infections, and therapy may be instituted before obtaining results of susceptibility testing. The decision to continue therapy with this drug should be based on the results of susceptibility tests, the severity of the infection and the important additional concepts contained in the BOXED WARNINGS. If the causative organisms are resistant to gentamicin, other appropriate therapy should be instituted.

In serious infections when the causative organisms are unknown, gentamicin injection may be administered as initial therapy in conjunction with a penicillin-type or cephalosporin-type drug before obtaining results of susceptibility testing. If anaerobic organisms are suspected as etiologic agents, consideration should be given to using other suitable antimicrobial therapy in conjunction with gentamicin. Following identification of the organism and its susceptibility, appropriate antibiotic therapy should then be continued.

Gentamicin injection has been used effectively in combination with carbenicillin for the treatment of life-threatening infections caused by Pseudomonas aeruginosa. It has also been found effective when used in conjunction with a penicillin-type drug for treatment of endocarditis caused by group D streptococci.

Gentamicin injection has also been shown to be effective in the treatment of serious staphylococcal infections. While not the antibiotic of first choice, gentamicin injection may be considered when penicillins or other less potentially toxic drugs are contraindicated and bacterial susceptibility tests and clinical judgment indicate its use. It may also be considered in mixed infections caused by susceptible strains of staphylococci and gram-negative organisms.

In the neonate with suspected bacterial sepsis or staphylococcal pneumonia, a penicillin-type drug is also usually indicated as concomitant therapy with gentamicin.

Bacterial infection due to Klebsiella pneumoniae
Bacterial infection due to Pseudomonas
Bacterial meningitis
Bacterial sepsis of newborn
Bacterial septicemia
Citrobacter infection
Eye infection
Infection due to Enterobacteriaceae
Infection due to Escherichia coli
Infection of bone
Infection of skin AND/OR subcutaneous tissue
Infective endocarditis
Peritonitis
Peritonitis, and other gastrointestinal tract infections
Respiratory tract infection
Serratia marcescens infection
Staphylococcal infectious disease
Urinary tract infectious disease
  • The recommended dosage of gentamicin injection for patients with serious infections and normal renal function is 3 mg/kg/day, administered in three equal doses every eight hours (Table 3).
  • For patients with life-threatening infections, dosages up to 5 mg/kg/day may be administered in three or four equal doses. This dosage should be reduced to 3 mg/kg/day as soon as clinically indicated (Table 3).
  • It is desirable to measure both peak and trough serum concentrations of gentamicin to determine the adequacy and safety of the dosage. When such measurements are feasible, they should be carried out periodically during therapy to assure adequate but not excessive drug levels. For example, the peak concentration (at 30 to 60 minutes after IM injection) is expected to be in the range of 4 to 6 mcg/mL. When monitoring peak concentrations after IM or IV administration, dosage should be adjusted so that prolonged levels above 12 mcg/mL are avoided. When monitoring trough concentrations (just prior to the next dose), dosage should be adjusted so that levels above 2 mcg/mL are avoided. Determination of the adequacy of a serum level for a particular patient must take into consideration the susceptibility of the causative organism, the severity of the infection and the status of the patient’s host-defense mechanisms.
  • In patients with extensive burns, altered pharmacokinetics may result in reduced serum concentrations of aminoglycosides. In such patients treated with gentamicin, measurement of serum concentrations is recommended as a basis for dosage adjustment.
This image is provided by the National Library of Medicine.
This image is provided by the National Library of Medicine.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

Condition1
  • Developed by:
  • Class of Recommendation:
  • Strength of Evidence:
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Guideline-Supported Use of Gentamicin in adult patients.

Non–Guideline-Supported Use

Condition1
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Non–Guideline-Supported Use of Gentamicin in adult patients.

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

Condition1
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding FDA-Labeled Use of Gentamicin in pediatric patients.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

Condition1
  • Developed by:
  • Class of Recommendation:
  • Strength of Evidence:
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Guideline-Supported Use of Gentamicin in pediatric patients.

Non–Guideline-Supported Use

Condition1
  • Dosing Information
  • Dosage
Condition2

There is limited information regarding Off-Label Non–Guideline-Supported Use of Gentamicin in pediatric patients.

Contraindications

  • Hypersensitivity to gentamicin is a contraindication to its use. A history of hypersensitivity or serious toxic reactions to other aminoglycosides may contraindicate use of gentamicin because of the known cross-sensitivity of patients to drugs in this class.

Warnings

See full prescribing information for complete Boxed Warning.
  • Patients treated with aminoglycosides should be under close clinical observation because of the potential toxicity associated with their use.
  • As with other aminoglycosides, gentamicin injection is potentially nephrotoxic. The risk of nephrotoxicity is greater in patients with impaired renal function and in those who receive high dosage of prolonged therapy.
  • Neurotoxicity manifested by ototoxicity, both vestibular and auditory, can occur in patients treated with gentamicin, primarily in those with pre-existing renal damage and in patients with normal renal function treated with higher doses and/or for longer periods than recommended. Aminoglycoside-induced ototoxicity is usually irreversible. Other manifestations of neurotoxicity may include numbness, skin tingling, muscle twitching and convulsions.
  • Renal and eighth cranial nerve function should be closely monitored, especially in patients with known or suspected reduced renal function at onset of therapy and also in those whose renal function is initially normal but who develop signs of renal dysfunction during therapy. Urine should be examined for decreased specific gravity, increased excretion of protein and the presence of cells or casts. Blood urea nitrogen (BUN), serum creatinine or creatinine clearance should be determined periodically. When feasible, it is recommended that serial audiograms be obtained in patients old enough to be tested, particularly high-risk patients. Evidence of ototoxicity (dizziness, vertigo, tinnitus, roaring in the ears or hearing loss) or nephrotoxicity requires dosage adjustment or discontinuance of the drug. As with the other aminoglycosides, on rare occasions changes in renal and eighth cranial nerve function may not become manifest until soon after completion of therapy.
  • Serum concentrations of aminoglycosides should be monitored when feasible to assure adequate levels and to avoid potentially toxic levels. When monitoring gentamicin peak concentrations, dosage should be adjusted so that prolonged levels above 12 mcg/mL are avoided. When monitoring gentamicin trough concentrations, dosage should be adjusted so that levels above 2 mcg/mL are avoided. Excessive peak and/or trough serum concentrations of aminoglycosides may increase the risk of renal and eighth cranial nerve toxicity.
  • In the event of overdosage or toxic reactions, hemodialysis may aid in the removal of gentamicin from the blood, especially if renal function is, or becomes, compromised. The rate of removal of gentamicin is considerably lower by peritoneal dialysis than it is by hemodialysis.
  • In the newborn infant, exchange transfusions may also be considered.
  • Concurrent and/or sequential systemic or topical use of other potentially neurotoxic and/or nephrotoxic drugs, such as cisplatin, cephaloridine, kanamycin, amikacin, neomycin, polymyxin B, colistin, paromomycin, streptomycin, tobramycin, vancomycin and viomycin, should be avoided. Other factors which may increase patient risk of toxicity are advanced age and dehydration.
  • The concurrent use of gentamicin with potent diuretics, such as ethacrynic acid or furosemide, should be avoided, since certain diuretics by themselves may cause ototoxicity. In addition, when administered intravenously, diuretics may enhance aminoglycoside toxicity by altering the antibiotic concentration in serum and tissue.
  • Aminoglycosides can cause fetal harm when administered to a pregnant woman.
  • Contains sodium metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than in non-asthmatic people.
  • Aminoglycosides can cause fetal harm when administered to a pregnant woman. Aminoglycoside antibiotics cross the placenta, and there have been several reports of total irreversible bilateral congenital deafness in children whose mothers received streptomycin during pregnancy. Serious side effects to mother, fetus or newborn have not been reported in the treatment of pregnant women with other aminoglycosides. Animal reproduction studies conducted on rats and rabbits did not reveal evidence of impaired fertility or harm to the fetus due to gentamicin sulfate.
  • It is not known whether gentamicin sulfate can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. If gentamicin is used during pregnancy or if the patient becomes pregnant while taking gentamicin, she should be apprised of the potential hazard to the fetus.

Precautions

  • Prescribing Gentamicin Injection, USP in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.
  • Neurotoxic and nephrotoxic antibiotics may be almost completely absorbed from body surfaces (except urinary bladder) after local irrigation and after topical application during surgical procedures. The potential toxic effects of antibiotics administered in this fashion (neuromuscular blockage, respiratory paralysis, oto- and nephrotoxicity) should be considered.
  • Neuromuscular blockade and respiratory paralysis have been reported in the cat receiving high doses (40 mg/kg) of gentamicin. The possibility of these phenomena occurring in man should be considered if aminoglycosides are administered by any route to patients receiving anesthetics, or to patients receiving neuromuscular blocking agents, such as succinylcholine, tubocurarine or decamethonium, or in patients receiving massive transfusions of citrate-anticoagulated blood. If neuromuscular blockade occurs, calcium salts may reverse it.
  • Elderly patients may have reduced renal function which may not be evident in the results of routine screening tests such as BUN or serum creatinine. A creatinine clearance determination may be more useful. Monitoring of renal function during treatment with gentamicin, as with other aminoglycosides, is particularly important in such patients. A Fanconi-like syndrome, with aminoaciduria and metabolic acidosis has been reported in some adults and infants being given gentamicin injections.
  • Cross-allergenicity among aminoglycosides has been demonstrated.
  • Patients should be well hydrated during treatment.
  • Although the in vitro mixing of gentamicin and carbenicillin results in a rapid and significant inactivation of gentamicin, this interaction has not been demonstrated in patients with normal renal function who received both drugs by different routes of administration. A reduction in gentamicin serum half-life has been reported in patients with severe renal impairment receiving carbenicillin concomitantly with gentamicin.
  • Treatment with gentamicin may result in overgrowth of nonsusceptible organisms. If this occurs, appropriate therapy is indicated.

Adverse Reactions

Clinical Trials Experience

  • Adverse renal effects, as demonstrated by the presence of casts, cells or protein in the urine or by rising BUN, NPN, serum creatinine or oliguria, have been reported. They occur more frequently in patients with a history of renal impairment (especially if dialysis is required) and in patients treated for longer periods or with larger doses than recommended.
  • Serious adverse effects on both vestibular and auditory branches of the eighth nerve have been reported, primarily in patients with renal impairment (especially if hemodialysis is required) and in patients on high doses and/or prolonged therapy. Symptoms include dizziness, vertigo, tinnitus, roaring in the ears and also hearing loss, which, as with the other aminoglycosides, may be irreversible. Hearing loss is usually manifested initially by diminution of high-tone acuity. Other factors which may increase the risk of toxicity include excessive dosage, dehydration and previous exposure to other ototoxic drugs.
  • Peripheral neuropathy or encephalopathy, including numbness, skin tingling, muscle twitching, convulsions and a myasthenia gravis-like syndrome have been reported.
  • NOTE: The risk of toxic reactions is low in patients with normal renal function who did not receive gentamicin sulfate at higher doses or for longer periods of time than recommended.
  • While the local tolerance of gentamicin sulfate is generally excellent, there has been an occasional report of pain at the injection site. Subcutaneous atrophy or fat necrosis suggesting local irritation has been reported rarely.

Postmarketing Experience

There is limited information regarding Postmarketing Experience of Gentamicin in the drug label.

Drug Interactions

There is limited information regarding Gentamicin Drug Interactions in the drug label.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA):

  • Pregnancy Category D


Pregnancy Category (AUS):

  • Australian Drug Evaluation Committee (ADEC) Pregnancy Category

There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Gentamicin in women who are pregnant.

Labor and Delivery

There is no FDA guidance on use of Gentamicin during labor and delivery.

Nursing Mothers

There is no FDA guidance on the use of Gentamicin with respect to nursing mothers.

Pediatric Use

There is no FDA guidance on the use of Gentamicin with respect to pediatric patients.

Geriatic Use

There is no FDA guidance on the use of Gentamicin with respect to geriatric patients.

Gender

There is no FDA guidance on the use of Gentamicin with respect to specific gender populations.

Race

There is no FDA guidance on the use of Gentamicin with respect to specific racial populations.

Renal Impairment

There is no FDA guidance on the use of Gentamicin in patients with renal impairment.

Hepatic Impairment

There is no FDA guidance on the use of Gentamicin in patients with hepatic impairment.

Females of Reproductive Potential and Males

There is no FDA guidance on the use of Gentamicin in women of reproductive potentials and males.

Immunocompromised Patients

There is no FDA guidance one the use of Gentamicin in patients who are immunocompromised.

Administration and Monitoring

Administration

  • Intravenous
  • Intramuscular

Monitoring

There is limited information regarding Monitoring of Gentamicin in the drug label.

IV Compatibility

There is limited information regarding IV Compatibility of Gentamicin in the drug label.

Overdosage

Acute Overdose

Chronic Overdose

There is limited information regarding Chronic Overdose of Gentamicin in the drug label.

Pharmacology

Template:Px
Template:Px
Gentamicin
Systematic (IUPAC) name
(3R,4R,5R)-2-{[(1S,2S,3R,4S,6R)-4,6-
diamino-3-{[(2R,3R,6S)-
3-amino-6-[(1R)-
1-(methylamino)ethyl]oxan-2-yl]oxy}-
2-hydroxycyclohexyl]oxy}-5-methyl-
4-(methylamino)oxane-3,5-diol
Identifiers
CAS number 1403-66-3
ATC code D06AX07 J01GB03 (WHO) S01AA11 (WHO) S02AA14 (WHO) S03AA06 (WHO) Template:ATCvet Template:ATCvet Template:ATCvet Template:ATCvet
PubChem 3467
DrugBank DB00798
Chemical data
Formula Template:OrganicBox atomTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox 
Mol. mass 477.596 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability limited oral bioavailability
Protein binding 0-10%
Metabolism ?
Half life 2 hrs
Excretion renal
Therapeutic considerations
Pregnancy cat.

D

Legal status

POM(UK)

Routes IV, Ophthalmic, IM, topical

Mechanism of Action

Structure

  • Gentamicin sulfate, a water-soluble antibiotic of the aminoglycoside group, is derived by the growth of Micromonospora purpurea, an actinomycete.
  • It has the following structural formula.
This image is provided by the National Library of Medicine.
  • Gentamicin injection is a sterile, nonpyrogenic aqueous solution for parenteral administration.
  • Each mL contains: Gentamicin sulfate equivalent to 40 mg gentamicin, methylparaben 1.8 mg and propylparaben 0.2 mg as preservatives, sodium metabisulfite 3.2 mg and edetate disodium 0.1 mg, Water for Injection q.s. Sodium hydroxide and/or sulfuric acid may have been added for pH adjustment.

Pharmacodynamics

There is limited information regarding Pharmacodynamics of Gentamicin in the drug label.

Pharmacokinetics

  • After intramuscular (IM) administration of gentamicin sulfate, peak serum concentrations usually occur between 30 and 60 minutes and serum levels are measurable for six to eight hours. When gentamicin is administered by intravenous (IV) infusion over a two-hour period, the serum concentrations are similar to those obtained by IM administration.
  • In patients with normal renal function, peak serum concentrations of gentamicin (mcg/mL) are usually up to four times the single IM dose (mg/kg); for example, a 1 mg/kg injection in adults may be expected to result in a peak serum concentration up to 4 mcg/mL; a 1.5 mg/kg dose may produce levels up to 6 mcg/mL. While some variation is to be expected due to a number of variables such as age, body temperature, surface area and physiologic differences, the individual patient given the same dose tends to have similar levels in repeated determinations. Gentamicin administered at 1 mg/kg every eight hours for the usual 7 to 10 day treatment period to patients with normal renal function does not accumulate in the serum.
  • Gentamicin, like all aminoglycosides, may accumulate in the serum and tissues of patients treated with higher doses and/or for prolonged periods, particularly in the presence of impaired renal function. In adult patients, treatment with gentamicin dosages of 4 mg/kg/day or higher for 7 to 10 days may result in a slight, progressive rise in both peak and trough concentrations. In patients with impaired renal function, gentamicin is cleared from the body more slowly than in patients with normal renal function. The more severe the impairment, the slower the clearance.(Dosage must be adjusted.)
  • Since gentamicin is distributed in extra-cellular fluid, peak serum concentrations may be lower than usual in adult patients who have a large volume of this fluid. Serum concentrations of gentamicin in febrile patients may be lower than those in afebrile patients given the same dose. When body temperature returns to normal, serum concentrations of the drug may rise. Febrile and anemic states may be associated with a shorter than usual serum half-life. (Dosage adjustment is usually not necessary). In severely burned patients, the half-life may be significantly decreased and resulting serum concentrations may be lower than anticipated from the mg/kg dose.
  • Protein binding studies have indicated that the degree of gentamicin binding is low; depending upon the methods used for testing, this may be between 0 and 30%.
  • After initial administration to patients with normal renal function, generally 70% or more of the gentamicin dose is recoverable in the urine in 24 hours; concentrations in urine above 100 mcg/mL may be achieved. Little, if any, metabolic transformation occurs; the drug is excreted principally by glomerular filtration. After several days of treatment, the amount of gentamicin excreted in the urine approaches the daily dose administered. As with other aminoglycosides, a small amount of the gentamicin dose may be retained in the tissues, especially in the kidneys. Minute quantities of aminoglycosides have been detected in the urine weeks after drug administration was discontinued. Renal clearance of gentamicin is similar to that of endogenous creatinine.
  • In patients with marked impairment of renal function, there is a decrease in the concentration of aminoglycosides in urine and in their penetration into defective renal parenchyma. This decreased drug excretion, together with the potential nephrotoxicity of aminoglycosides, should be considered when treating such patients who have urinary tract infections.
  • Probenecid does not affect renal tubular transport of gentamicin.
  • The endogenous creatinine clearance rate and the serum creatinine level have a high correlation with the half-life of gentamicin in serum. Results of these tests may serve as guides for adjusting dosage in patients with renal impairment.
  • Concentrations in renal cortex sometimes may be eight times higher than the usual serum levels. Concentrations in bile, in general, have been low and have suggested minimal biliary excretion. Gentamicin crosses the peritoneal as well as the placental membranes. Since aminoglycosides diffuse poorly into the subarachnoid space after parenteral administration, concentrations of gentamicin in cerebrospinal fluid are often low and dependent upon dose, rate of penetration and degree of meningeal inflammation. There is minimal penetration of gentamicin into ocular tissues following IM or IV administration.
Microbiology
  • Drug Resistance
  • Bacterial resistance to gentamicin is generally developed slowly. Bacteria resistant to one aminoglycoside may be resistant to one or more other aminoglycosides. The following bacteria are usually resistant to the aminoglycosides, including gentamicin: most streptococcal species (including Streptococcus pneumoniae and the Group D streptococci), most enterococcal species (including Enterococcus faecalis, E. faecium, and E. durans), and anaerobic organisms, such as Bacteroides species and Clostridium species.
  • Aminoglycosides are known to be not effective against Salmonella and Shigella species in patients. Therefore, in vitro susceptibility test results should not be reported.
  • Interactions with Other Antimicrobials
  • In vitro studies show that an aminoglycoside combined with an antibiotic that interferes with cell wall synthesis may act synergistically against some enterococcal strains. The combination of gentamicin and penicillin G has a synergistic bactericidal effect against strains of Enterococcus faecalis, E. faecium and E. durans. An enhanced killing effect against many of these strains has also been shown in vitro with combinations of gentamicin and ampicillin, carbenicillin, nafcillin or oxacillin.
  • The combined effect of gentamicin and carbenicillin is synergistic for many strains of Pseudomonas aeruginosa. In vitro synergism against other Gram-negative organisms has been shown with combinations of gentamicin and cephalosporins.
  • Gentamicin may be active against clinical isolates of bacteria resistant to other aminoglycosides.
  • Antibacterial Activity
  • Gentamicin has been shown to be active against most of the following bacteria, both in vitro and in clinical infections.
  • Gram-Positive Bacteria

Staphylococcus species

Citrobacter species Enterobacter species Escherichia coli Klebsiella species Proteus species Serratia species Pseudomonas aeruginosa

  • Susceptibility Test Methods
  • When available, the clinical microbiology laboratory should provide cumulative results of the in vitro susceptibility tests for antimicrobial drugs used in local hospitals and practice areas to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting the most effective antimicrobial.
  • Dilution Technique
  • Quantitative methods are used to determine antimicrobial minimal inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method.1, 3 Standardized procedures are based on a dilution method (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of gentamicin powder. The MIC values should be interpreted according to the criteria provided in Table 1.
  • Diffusion Technique
  • Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure requires the use of standardized inoculum concentrations and paper disks impregnated with 10 mcg of gentamicin. 2, 3 The disk diffusion values should be interpreted according to the criteria provided in Table 1.
This image is provided by the National Library of Medicine.
  • aFor Salmonella and Shigella spp., aminoglycosides may appear active in vitro but are not effective clinically; the results should not be reported as susceptible
  • bFor staphylococci that test susceptible, aminoglycosides are used only in combination with other active agents that test susceptible
  • A report of “Susceptible” indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentration at the infection site necessary to inhibit growth of the pathogen. A report of “Intermediate” indicates that the result should be considered equivocal, and if the microorganism is not fully susceptible to alternative clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of “Resistant” indicates that the antimicrobial is not likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations usually achievable at the infection site; other therapy should be selected.
  • Quality Control
  • Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test.1, 2, 3 Standard gentamicin powder should provide the following range of MIC values provided in Table 2. For the diffusion technique using the 10-mcg gentamicin disk the criteria provided in Table 2 should be achieved.
This image is provided by the National Library of Medicine.

Nonclinical Toxicology

There is limited information regarding Nonclinical Toxicology of Gentamicin in the drug label.

Clinical Studies

There is limited information regarding Clinical Studies of Gentamicin in the drug label.

How Supplied

  • Gentamicin Injection, USP, containing gentamicin 40 mg/mL is supplied as follows:
This image is provided by the National Library of Medicine.
  • Also available, Gentamicin Injection (Pediatric), 10 mg/mL, supplied in 2 mL (20 mg) vials in packages of 25.
  • Store at 20° to 25°C (68° to 77°F).
  • This container closure is not made with natural rubber latex.

Storage

There is limited information regarding Gentamicin Storage in the drug label.

Images

Drug Images

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Package and Label Display Panel

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Patient Counseling Information

  • Patients should be counseled that antibacterial drugs including Gentamicin Injection, USP should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Gentamicin Injection, USP is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Gentamicin Injection, USP or other antibacterial drugs in the future.

Precautions with Alcohol

  • Alcohol-Gentamicin interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

Brand Names

Look-Alike Drug Names

There is limited information regarding Gentamicin Look-Alike Drug Names in the drug label.

Drug Shortage Status

Price

References

The contents of this FDA label are provided by the National Library of Medicine.

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