Gentamycin Sulfate Injection

Action And Clinical Pharmacology: Gentamicin exerts its bactericidal effect by specific inhibition of normal protein synthesis in susceptible bacteria. It binds primarily to the 30S subunit of bacterial ribosomes.
Gentamicin is poorly absorbed following oral administration and must be given parenterally for systemic use. When administered I. M., peak serum concentrations are attained in 0.5 to 1 hour. Peak serum concentrations following I. V. Administration occur at the end of the infusion and vary with the rate of infusion. The serum elimination half-life is about 2 hours in patients with normal renal function.

Gentamicin is excreted by the kidney in unchanged form, mostly by glomerular filtration. After initial administration of gentamicin, 30 to 100% of the dose is recoverable in the urine in 24 hours in patients with normal renal function. Approximately 30% is excreted in 12 hours in the newborn.
Gentamicin Serum Levels via the I. M. Route in Adults: Peak bactericidal serum concentrations for susceptible bacteria in patients with normal renal function occur between 30 and 90 minutes after injection. The peak serum level (µ G/mL) was found to be 4 times the single dose (mg/kg), and the mean serum half-life is approximately 2 hours.

In contrast, full-term infants 7 days of age and older have half-lives of about 3 to 3.5 hours. I. M. Doses of 2 and 2.5 mg/kg administered to infants 2 to 24 months of age resulted in gentamicin serum concentrations in the range of 2.5 to 7.5 µ G/mL.
Gentamicin Serum Levels via the I. V. Route in Adults: Peak gentamicin concentrations were reached at the end of a 2-hour infusion of a dose of 1 mg/kg to a group of patients and averaged 4.5 µ G/mL (range 0.5 to 8 µ G/mL).
Serum levels of 5 to 9 µ G/mL were obtained following slow I. V. Injection after 10 minutes at recommended doses.
The mean serum half-life is approximately 2 hours which is the same as for the I. M. Route of administration.
Gentamicin Serum Levels via the I. V. Route in Infants and Neonates: Half-life values and serum gentamicin levels after I. V. Infusion were similar to those after I. M. Administration.
Approximately 30% of the administered dose is excreted in 12 hours in the newborn.

Indications And Clinical Uses: In the treatment of serious infections caused by susceptible strains of the following microorganisms: P. Aeruginosa, Proteus species (indole negative and indole positive), E. Coli, K. Pneumoniae, E. Aerogenes, S. Marcescens, Staphylococcus species (including penicillin and methicillin-resistant strains).
Gentamicin may be considered for the treatment of the following: (1) bacteremia (2) respiratory tract infections (3) urinary tract infections (4) infected wounds: Surgical and traumatic (5) soft tissue infections, including peritonitis and burns complicated by sepsis (6) bone infections.
Susceptibility: In the majority of cases, appropriate cultures and susceptibility studies should be obtained initially to identify the causative organism and to determine its sensitivity to gentamicin.
The decision to continue therapy with gentamicin injection should be based on consideration of relative antibiotic toxicity, results of the sensitivity tests and the clinical response of the patient.

Dosage And Administration: I. M. Injection is the usual route of administration for gentamicin injection. Administration via the I. V. Route is generally reserved for special indications (see I. V. Administration). Treatment usually lasts from 7 to 10 days. A longer course of therapy may be necessary, however, in difficult and complicated infections. Monitoring of vestibular, auditory and renal functions is advisable in such cases.
The recommended dosage for children 1 to 12 years of age is 3 to 6 mg/kg/day in 3 equal doses every 8 hours for severe infections. If a dosage greater than 3 mg/kg/day is initially administered, it should be reduced to 3 mg/kg/day when clinically indicated.