gen·ta·mi·cin sulfate or gen·ta·my·cin sulfate (j n t -m  s n)n. A broad-spectrum antibiotic derived from an actinomycete used in the treatment of various infections. |
gentamicin sulfate
gentamicin sulfate,
brand names: Garamycin Ophthalmic, Gentak;
drug class: aminoglycoside antiinfective ophthalmic; action: inhibits bacterial protein synthesis;
use: infection of external eye.
gentamicin sulfate
Cidomycin (CA) (UK), Garamycin, Gentacidin, Gentak, Genticin (UK)
Pharmacologic class: Aminoglycoside
Therapeutic class: Anti-infective
Pregnancy risk category D (parenteral), C (topical)
FDA Boxed Warning
• Observe patient closely for potential ototoxicity and nephrotoxicity. Safety isn't established in therapy exceeding 14 days.
• Neuromuscular blockade and respiratory paralysis have occurred after administration.
• Monitor renal function and eighth-nerve function closely, especially in patients with known or suspected renal impairment at onset of therapy, as well as those with initially normal renal function who develop signs of renal dysfunction during therapy.
• Avoid concurrent use with potent diuretics (such as furosemide and ethacrynic acid), because diuretics may cause ototoxicity. Also, I.V. diuretics may increase gentamicin toxicity by altering antibiotic serum and tissue levels.
• Avoid concurrent and sequential systemic, oral, or topical use of other neurotoxic or nephrotoxic products and other aminoglycosides. Advanced age and dehydration also may increase toxicity risk.
• Drug may harm fetus when given to pregnant women.
Action
Destroys gram-negative bacteria by irreversibly binding to 30S subunit of bacterial ribosomes and blocking protein synthesis, resulting in misreading of genetic code and separation of ribosomes from messenger RNA
Availability
Cream: 0.1%
Injection: 10 mg/ml (pediatric), 40 mg/ml (adult)
I.V. infusion (premixed in normal saline solution): 40 mg, 60 mg, 70 mg, 80 mg, 90 mg, 100 mg, 120 mg
Ointment: 0.1%
Ointment (ophthalmic): 0.3% (base)
Solution (ophthalmic): 0.3% (base)
⊘Indications and dosages
➣ Serious infections caused by Pseudomonas aeruginosa, Escherichia coli, and Proteus, Klebsiella, Serratia, Enterobacter, Citrobacter, or Staphylococcus species
Adults: 3 mg/kg/day in three divided doses I.M. or I.V. infusion q 8 hours. For life-threatening infections, up to 5 mg/kg/day in three to four divided doses; reduce to 3 mg/kg/day as indicated.
Children: 2 to 2.5 mg/kg q 8 hours I.M. or I.V. infusion
Infants older than 1 week: 2.5 mg/kg q 8 hours I.M. or I.V. infusion
Neonates younger than 1 week, preterm infants: 2.5 mg/kg q 12 hours I.M. or I.V. infusion. In preterm infants of less than 32 weeks' gestational age, 2.5 mg/kg q 18 hours or 3 mg/kg q 24 hours also may produce satisfactory peak and trough blood levels.
➣ Endocarditis prophylaxis before surgery
Adults: 1.5 mg/kg I.M. or I.V. 30 minutes before surgery, to a maximum of 80 mg. As prescribed, give with ampicillin or vancomycin.
Children: 2 mg/kg I.M. or I.V. 30 minutes before surgery, to a maximum of 80 mg
➣ External ocular infections caused by susceptible organisms
Adults and children: One to two drops of ophthalmic solution in eye q 4 hours. For serious infections, up to two drops q hour, or ophthalmic ointment applied to lower conjunctival sac two to three times daily.
➣ Treatment and prevention of superficial burns caused by susceptible bacteria
Adults and children older than age 1: Gently rub small a amount of drug topically on affected area three or four times daily.
Dosage adjustment
• Renal impairment
• Cystic fibrosis
Contraindications
• Hypersensitivity to drug or other aminoglycosides
Precautions
Use cautiously in:
• neuromuscular disease, renal impairment, hearing impairment
• sulfite sensitivity (with parenteral use)
• obese patients
• elderly patients
• pregnant or breastfeeding patients
• infants, neonates, and premature infants.
Administration
• Before starting therapy, obtain specimens as needed for culture and sensitivity testing.
• For I.V. infusion, dilute with 50 to 200 ml of dextrose 5% in water (D5W) or normal saline solution, and administer over 30 minutes to 2 hours.
• After infusion, flush line with normal saline solution or D5W.
• Obtain peak drug blood level 30 minutes after 30-minute infusion; obtain trough level within 30 minutes of next scheduled dose.
• Give cephalosporin or parenteral penicillin 1 hour before or after gentamicin, as prescribed.
• Know that for topical treatment of burns, gauze dressings may be applied.
| Route | Onset | Peak | Duration |
| I.V. | Immediate | 30-90 min | Unknown |
| I.M. | Unknown | 30-90 min | Unknown |
| Topical, ophthalmic | Unknown | Unknown | Unknown |
Adverse reactions
CNS: dizziness, vertigo, tremors, numbness, depression, confusion, lethargy, headache, paresthesia, neuromuscular blockade, seizures, neurotoxicity
CV: hypotension, hypertension, palpitations
EENT: visual disturbances, dry eyes, nystagmus, photophobia, ototoxicity, hearing loss, tinnitus
GI: nausea, vomiting, stomatitis, increased salivation, splenomegaly, anorexia
GU: increased urinary casts, polyuria, dysuria, erectile dysfunction, azotemia, nephrotoxicity
Hematologic: eosinophilia, leukemoid reaction, hemolytic anemia, aplastic anemia, neutropenia, agranulocytosis, leukopenia, thrombocytopenia, pancytopenia
Hepatic: hepatomegaly, hepatotoxicity, hepatic necrosis
Musculoskeletal: joint pain, muscle twitching
Respiratory: apnea
Skin: exfoliative dermatitis, rash, pruritus, urticaria, purpura, alopecia
Other: weight loss, superinfection, pain and irritation at I.M. injection site
Interactions
Drug-drug. Acyclovir, amphotericin B, carboplatin, cephalosporins, cisplatin, loop diuretics, vancomycin, other ototoxic or nephrotoxic drugs: increased risk of ototoxicity and nephrotoxicity
Dimenhydrinate, other antiemetics: masking of ototoxicity symptoms
General anesthetics, neuromuscular blockers: increased activity of these drugs
Indomethacin: increased gentamicin peak and trough levels
Penicillins (such as ampicillin, ticarcillin): synergistic effect
Tacrolimus: nephrotoxicity
Drug-diagnostic tests. Alanine aminotransferase, aspartate aminotransferase, bilirubin, blood urea nitrogen (BUN), creatinine, lactate dehydrogenase: increased values
Granulocytes, hemoglobin, platelets, white blood cells: decreased values
Reticulocytes: increased or decreased count
Patient monitoring
• Watch for signs and symptoms of hypersensitivity reactions.
☞ Know that drug blood level monitoring is especially important in therapy lasting more than 5 days, acute or chronic renal impairment, extracellular fluid volume changes, obesity, infants younger than 3 months, concomitant use of nephrotoxic drugs, patients requiring higher doses or dosage interval adjustments (such as those with cystic fibrosis, endocarditis, or critical illness), and patients with signs or symptoms of nephrotoxicity or ototoxicity.
• Assess fluid intake and output, urine specific gravity, and urinalysis for signs of nephrotoxicity.
• Monitor CBC, BUN, creatinine level, and creatinine clearance.
• Weigh patient regularly.
• Assess for signs and symptoms of ototoxicity (hearing loss, tinnitus, ataxia, and vertigo).
Patient teaching
☞ Teach patient to recognize and immediately report signs and symptoms of hypersensitivity reaction, infection, unusual tiredness, yellowing of skin or eyes, and muscle twitching.
• Advise patient to report signs and symptoms of ototoxicity (hearing loss, ringing in ears, vertigo).
• Instruct patient to drink plenty of fluids to ensure adequate urine output.
• Tell patient to monitor urine output and report significant changes.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
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