Inhibits protein synthesis by binding directly to the 30S ribosomal subunit. Usually bactericidal.
INDICATIONS & DOSAGE
Serious infections due to sensitive strains of Pseudomonas aeruginosa, Escherichia coli, Proteus, Klebsiella, Serratia, Enterobacter, Citrobacter, or Staphylococcus
Adults: 3 mg/kg daily in divided doses I.M. or I.V. infusion q 8 hours. For life threatening infections, patient may receive up to 5 mg/kg daily in three to four divided doses; dose should be reduced to 3 mg/kg daily as soon as clinically indicated.
Children: 2 to 2.5 mg/kg q 8 hours I.M. or by I. V. infusion.
Neonates over age 1 week or infants: 2.5 mg/kg q 8 hours I.M. or by I. V. infusion.
Neonates under age 1 week and pretenn infants: 2.5 mg/kg q 12 hours I.M. or by I.V. infusion.
Adults: systemic therapy as above.
Children: systemic therapy as above.
Endocarditis prophylaxis for GI or GU procedure or surgery-
Adults: 1.5 mg/kg LM. or LV. 30 minutes before procedure or surgery. Maximum dose is 80 mg. Given with ampicillin (vancomycin in penicillinallergic patients).
Children: 2 mg/kg LM. or I.V. 30 minutes before procedure or surgery. Maximum dose is 80 mg. Given with ampicillin (vancomycin in penicillin allergic patients).
After hemodialysis to maintain therapeutic blood levels -
Adults: 1 to 1.7 mg/kg I.M. or by LV. inusion after each dialysis.
Children: 2 to 2.5 mg/kg LM. or by 1. V. infusion after each dialysis.
Dosage adjustment: For adult patients with impaired renal function, doses and frequency are determined by serum gentamicin levels and renal function.
CNS: headache, lethargy, encephalopathy, confusion, dizziness, seizures, numbness, peripheral neuropathy, vertigo, ataxia, tingling.
EENT: ototoxicity, blurred vision, tinnitus.
GI: vomiting, nausea.
GU: nephrotoxicity; possible elevation in BUN, nonprotein nitrogen, or serum creatinine levels; possible increase in urinary excretion of casts.
Hematologic: anemia, eosinophilia, leukopenia, thrombocytopenia, agranulocytosis.
Hepatic: increased ALT, AST, bilirubin, LD.
Musculoskeletal: muscle twitching, myasthenia gravis-like syndrome.
Skin: rash, urticaria, pruritus.
Other: fever, anaphylaxis; injection site pain.
Drug-drug. Acyclovir, amphotericin B, cisplatin, methoxyflurane, vancomycin, other aminoglycosides: increased ototoxicity and nephrotoxicity. Use together cautiously.
Cephalosporins: increased nephrotoxicity. Use together cautiously. Dimenhydrinate: may mask symptoms of ototoxicity. Use with caution.
General anesthetics, neuromuscular blockers: may potentiate neuromuscular blockade. Monitor closely.
Indomethacin: may increase serum peak and trough levels of gentamicin. Serum gentamicin ]evels must be monitored closely.
I. V. loop diuretics (such as furosemide): increased ototoxicity. Use cautiously. Parenteral penicillins (such as ampicillin and ticarcillin): gentamicin inactivation in vitro. Don’t mix together.
EFFECTS ON DIAGNOSTIC TESTS
Contraindicated in hypersensitivity to drug or other aminoglycosides
• Use cautiously in neonates, infants, elderly patients, and patients with impaired renal function or neuromuscular disorders.
• A specimen for culture and sensitivity tests is obtained before first dose is given.
• Patient’s hearing must be evaluated before and during therapy. Patient complaints of tinnitus, vertigo, or hearing loss are important.
• Patient’s weight and renal function studies must be reviewed before therapy begins.
• Alert: Preservative-free formulations of gentamicin are used when the intrathecal route is ordered.
• Blood for peak gentamicin level is obtained I hour after I.M. injection or 30 minutes after LV. infusion finishes; for trough levels, blood is drawn just before next dose. Blood must not be collected in a heparinized tube; heparin is incompatible with aminoglycosides.
• Peak blood levels over 10 mcg/ml and trough levels over 2 mcg/m] may be associated with higher incidence of toxicity.
• Urine output, specific gravity, urina]ysis, BUN and creatinine levels, and creatinine clearance must be monitored.
• Hemodialysis for 8 hours removes up to 50% of drug from blood.
• Superinfection (continued fever and other signs and symptoms of new infection, especially of upper respiratory tract) may occur.
• Therapy usually continues for 7 to 10 days. If no response occurs in 3 to 5 days, therapy may be stopped and new specimens obtained for culture and sensitivity testing.