Indication
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Treatment of gram-negative infections.
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Action
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Bactericidal agent that acts by inhibiting protein synthesis in susceptible bacteria.
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Drug type
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Aminoglycoside antibiotic
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Trade name
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DBL gentamicin, Gentamicin BP (Pfizer)
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Presentation
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10 mg/mL ampoule – paediatric strength
80 mg/2 mL ampoule – adult strength
NOTE: SAS product may be considered in the event of a shortage. Consult the local pharmacy.
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Dose
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Dose: 5 mg/kg as follows: (2-5)
Corrected Gestational Age/Postmenstrual Age*
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Route
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Dosing interval
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Drug concentration to be performed at:
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< 30+0 weeks*
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IV/IM
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48 hourly
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22 hours after the 2nd dose
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30+0─34+6 weeks*
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IV/IM
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36 hourly
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22 hours after the 2nd dose
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≥ 35+0 weeks*
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IV/IM
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24 hourly
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22 hours after the 2nd dose
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*Concurrent cyclo-oxygenase inhibitors (indomethacin or ibuprofen) (6-8)
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IV/IM
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Extend dosing interval by 12 hours
Example:
48 hourly to 60 hourly
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Therapeutic hypothermia (9-13)
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IV/IM
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36 hourly
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Trough concentrations prior to every dose
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Subsequent dose interval is based on a gentamicin concentration at 22 hours after the administration of the 2nd dose as indicated in the table below.(3, 4)
22-hour Gentamicin concentration*
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Interval
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≤ 1.2 mg/L
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Every 24 hours after previous dose
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1.3 mg/L ─ 2.6 mg/L
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Every 36 hours after previous dose
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2.7 mg/L ─ 3.5 mg/L
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Every 48 hours after previous dose
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≥ 3.6 mg/L
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Hold dose, repeat concentration 24 hours later
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*Different to trough concentration performed prior to next dose – Refer to dose adjustment section.
Gentamicin monitoring is required ONCE only, except when the duration of gentamicin therapy is greater than 7 days or with the conditions described in dose adjustment and monitoring section.
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Dose adjustment
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Therapeutic hypothermia –36 hourly interval(9-13). Measure trough concentrations before every dose.
ECMO - Renal dysfunction is the main determinant. Measure trough concentration before 2nd dose.(14)
Renal impairment – Measure trough concentration before every dose.
Hepatic impairment – No specific dose adjustment.
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Maximum dose
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Total cumulative dose
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Route
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IV
IM – only if IV access is not available.
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Preparation
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10mg/mL – paediatric strength
Draw up 1mL (10mg) gentamicin and add to 4mL of sodium chloride 0.9% to make a final volume of 5mL with a concentration of 2mg/mL solution.
80mg/2 mL – adult strength
Draw up 1mL (40mg) gentamicin and add to 19mL of sodium chloride 0.9% to make a final volume of 20mL with a concentration of 2mg/mL solution.
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Administration
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IV - Inject slowly over 5 minutes as an IV injection.(15)
IM- only given when IV route is not available as the IM absorption is variable. Administer required dose undiluted, deeply into anterolateral thigh muscle.
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Monitoring
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Urine output, urine analysis, blood urea, nitrogen and creatinine
Monitor for anaphylaxis
Trough concentrations – Target trough concentration: <2 mg/L. Repeat trough concentrations are not required routinely unless: (4)
duration of therapy is ≥ 7 days – In this scenario, prior to dose on day 7 and then weekly thereafter.
renal impairment or perinatal hypoxia with Apgar <5 at 5 minutes and/or concomitant use of other nephrotoxic agents or therapeutic hypothermia In these scenarios, perform trough concentration prior to every dose.
If trough concentration ≥2 mg/L, withhold the dose, repeat trough concentrations before the subsequent dosing and discuss with infectious disease specialist/clinical microbiologist for either extended dosing interval or alternate antibiotic.
Peak concentrations - Not required routinely. Target peak concentrations: 5-12 mg/L. Peak concentration should be drawn at 30 minutes post dose.
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