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Gentamicin sulphate

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Dose and administration

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  1. Intravenous infusion over 20 to 30 minutes, or IM injection.
  2. There is no loading dose to be administered. 
  3. Obtain trough level and serum creatinine level prior to the second dose and withhold the dose while result is awaited (unless gentamicin is due to be stopped at 48 hours). See Special Considerations below. 
Postmenstrual Age (weeks) Postnatal Age (days) Dose (mg/kg/dose) Interval (hours)
≤29  (or significant asphyxia) 0 to 7 5 mg/kg 48 hourly
8 - 30 5 mg/kg 36 hourly
> 30 5 mg/kg 24 hourly
30 to 36 0 to 7 5 mg/kg 36 hourly
> 7 4 mg/kg 24 hourly
≥37 Any 4 mg/kg 24 hourly

Indications

  1. Empirical therapy for those VLBW infants with risk factors for perinatal sepsis in the first week of life.
  2. Proven neonatal sepsis (pneumonia, septicaemia, urinary tract infections, CNS infections, skin, bone and soft tissue infection), with bacteria known to be sensitive (note: Staph epidermidis is resistant).

Contraindications and precautions

  1. Known hypersensitivity to gentamicin/other aminoglycosides.
  2. Use in treatment of minor infections.
  3. Extreme caution in neonates with renal dysfunction.
  4. Caution in concurrent therapy with cephalosporins, potent diuretics such as furosemide, and neuromuscular blocking agents.
  5. Concurrent administration with other ototoxic and/or nephrotoxic drugs.

Clinical pharmacology

Bacteriocidal aminoglycoside antibiotic which inhibits bacterial protein synthesis. Active against a wide variety of pathogenic gram negative and gram positive bacteria, including Escherichia coli, Enterbacter spp, Pseudomonas aeruginosa, Proteus spp, Serratia spp, Staphylococcus spp (including penicillin and methicillin resistant strains).

Poorly absorbed by the oral route, variable absorption from intramuscular injection sites. Diffuses through the plasma and interstitial fluid volumes. Does not penetrate the CSF to any significant extent. Low binding (25-30%) to human plasma protein. Thought to be excreted unchanged, eliminated mainly by the kidney. Renal clearance of gentamicin appears to be slightly less than that of endogenous creatinine. Reduction in serum concentrations can be achieved by peritoneal dialysis or haemodialysis.

Possible adverse effects

  • Nephrotoxicity (transient and reversible renal tubular dysfunction).
  • Ototoxicity (vestibular injury irreversible. More likely to occur if Gentamicin used concomitantly with other nephrotoxic medications).
  • Neurotoxicity (neuromuscular weakness and respiratory failure potentiated with concomitant treatment with neuromuscular blocking agents or in patients with hypermagnesaemia).
  • Venous irritation, soft tissue injury at IV injection site.
  • Pain, soft tissue injury at IM injection site.
  • Gastrointestinal (elevated liver enzymes).
  • Blood dyscrasias (rare).
  • Hypersensitivity (rash, urticaria, fever, laryngeal oedema).

Special considerations

  1. May be used in combination with other antibiotics if infused separately.
  2. Adjust dose and/or dose interval in infants with suspected/proven renal impairment, or reduced renal clearance due to extreme immaturity.
  3. Monitoring:
    1. For infants who are likely to have their antibiotics ceased at 48 hours, levels are not necessary unless there is concern about renal impairment.
    2. Obtain trough level and serum creatinine level prior to the second dose and withhold the dose while result is awaited. Adjust dosing interval according to trough level.
    3. Repeat trough levels prior to the next dose if Gentamicin dose or interval is changed.
    4. Repeat trough and serum creatinine levels every 3-5 days unless there is suspected or known renal impairment and/or co-infusion of other nephrotoxic medications, in which case the trough and serum creatinine levels will need to be monitored more frequently.
    5. Trough level immediately prior to the next dose should be < 1 mg/L.
    6. Peak level, if required should be taken 60 minutes after the start of drug administration. Note peak levels only need to be measured when using a non standard treatment policy, which should only be in consultation with the Paediatric Infectious Diseases Services. The desired peak levels should be discussed with Paediatric Infectious Diseases Specialist.
  4. Ototoxicity risk is difficult to predict and can occur despite target serum trough levels especially in infants with other risk factors. All infants treated with Gentamicin for longer than 48 hours should have audiology testing.

Management of Gentamicin administration

Description

Clear solution in ampoules 10 mg/ml.

Prescription

  • Stat doses to be charted on stat page of prescription chart in mg/dose.
  • Maintenance doses are charted on the prescription chart in mg/dose.

Administration

Slow IV Infusion

  1. Dilution not required unless baby <1000 grams.
  2. Dilute to 2 mg/ml for use in ELBW infants.
  3. Administer by IV infusion via BBraun pump over 20-30 minutes. Filter prior to administration through a Pall (0.2 micron) filter.
  4. Compatible with D5W, D10W, 0.9% NaCl and IVN. Incompatible with Intralipid.
  5. Do NOT mix with other drugs, blood or blood products.
  6. Flush before and after administration of gentamicin with 0.9% NaCl

Observation and documentation

  1. Observe for signs of adverse effects.
  2. Observe for signs of renal, hepatic and haematological dysfunction during prolonged therapy.

Storage

  • Unopened at room temperature <25°C.
  • Use immediately after opening.

References

  1. Neonatal Formulary BMJ Books 6th Edition 2011 p 120
  2. Young TE, Magnum B. Neofax 16th Edition 2003 A Manual of Drugs Used in Neonatal Care.
  3. Begg EJ, Barclay ML, Kirkpatrick CMJ. The therapeutic monitoring of antimicrobial agents. Br J Clin Pharmacol. 2001:52; 35S-43S
  4. Hoff D S, Wilcox RA, Tollefson LM, Lipnik PG, Commers AR, Liu M. Pharmacokinetic Outcomes of a Simplified, Weight-Based, Extended-Interval Gentamicin Dosing Protocol in Critically Ill Neonates. Pharmacotherapy. 2009.29: 1; 1297-1305
  5. Best EJ, Gazarian M, Cohn R, Wilkinson M, Palasanthiran P. One-daily Gentamicin in infants and children. A prospective cohort study evaluating safety and the role of therapeutic drug monitoring in minimizing toxicity. Pediatr Infect Dis J. 2011. 30:10;827-32
  6. Koren T, Leeder S, Harding E. Optimisation of gentamicin therapy in very low birthweight infants. Pediatr Pharmacol 1985; 5:79.
  7. Heindmarsh KW, Nation RL, Williams GL, et al. Pharmacokinetics of gentamicin in very low birthweight preterm infants. Eur J Clin Pharmacol 1983; 24:649. 

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Document Control

  • Date last published: 24 April 2012
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years