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Drug dosage identifier


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Dose and administration

  • 50mg/kg/dose by slow IV injection. IM route may be used if IV access is unavailable, but is painful and has a slower onset of action. 
  • Oral 25mg/kg/dose. 
  • Dosing interval as below.
  • Maximum daily dose: 200mg/kg/day
Postnatal Age (days) Dose Interval (hours)
Day 0-7 12
Day 8-28 8
Day 29+ 6


  1. Empirical therapy for infants with suspected coagulase negative staphylococcal sepsis but resistance is now increasingly common. May be administered in combination with amoxycillin and amikacin until culture results available.
  2. Skin and soft tissue infections.
  3. Bone and joint infections.

Contraindications and precautions

  1. Hypersensitivity to penicillins/cephalosporins.
  2. Caution in preterm infants and those with jaundice, as flucloxacillin can displace bilirubin from albumin.
  3. Caution in infants with liver, renal or gastrointestinal disease.

Clinical pharmacology

Semi-synthetic narrow spectrum bacteriocidal antibiotic with considerable activity against penicillinase producing coagulase negative staphylococci and Staphylococcus aureus. Has little activity against gram negative bacilli. Action through inhibition of biosynthesis of cell wall mucopeptides.

Well absorbed after oral administration, although absorption is reduced in the presence of food and unpredictable in neonates. Widely distributed at varying concentrations in human body tissues and fluids. Very little passes into the CSF unless the meninges are inflamed. Highly bound (92%) to human plasma proteins. Excreted, mainly unchanged, by the kidney. Tubular excretion is inhibited by probenecid.

Possible adverse effects

  1. Venous irritation, soft tissue injury at site of IV injection.
  2. Pain, soft tissue injury at site of IM injection.
  3. Gastrointestinal disturbance (nausea, vomiting, diarrhoea).
  4. Non-specific rashes and skin eruptions.
  5. Fever, pruritus, urticaria.
  6. Seizures (encephalopathy with high doses greater than 400 mg/kg/day).
  7. Hepatitis & cholestatic jaundice, possibly occurring up to several weeks after discontinuation, has been reported occasionally in adults.

Special considerations

  1. May give concurrently with aminoglycoside therapy for synergistic effect. Administer separately as simultaneous administration may cause inactivation, and precipitation.
  2. Adjust dose in suspected significant renal dysfunction (usually by lengthening the dosing interval).
  3. Give 30-60 minutes before feeds.

Management of Flucloxacillin administration


IV:  White powder for reconstitution 250 mg/vial. Reconstituted solution is a pale straw colour. pH 5-7.

Oral:  Free-flowing white granular powder with a slight lemon odour. Reconstituted solution is opaque, off-white in colour with a lemon odour.


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


Slow IV Injection

  1. Make up immediately prior to use.
  2. Reconstitute with water to 100 mg/ml.

       Flucloxin 250mg
    Powder space: 0.2ml
    Water to be added: 2.3ml
    Resultant concentration: 100mg/ml
  3. Shake vigorously.
  4. .Dilute immediately prior to use to 50 mg/ml by adding to 0.9% sodium chloride.
  5. Filter prior to administration through a Pall 0.22 micron filter. Administer by slow IV injection over 3-5 minutes.
  6. Compatible with 0.9% sodium chloride or 5% glucose. Incompatible with aminoglycosides.
  7. Do NOT mix with other drugs, IV solutions, blood or blood products.
  8. Flush line with 0.9% sodium chloride before and after administration of flucloxacillin.

Oral administration

  1. Reconstitute with water. Add 87ml of purified water to dry mixture in the bottle. Shake well.
  2. Shake well before use.
  3. Administer on an empty stomach as far as possible - 30-60 minutes before feeds.

Nursing considerations

  1. Assess IV site carefully before and during injection of flucloxacillin for extravasation.
  2. Observe for signs of adverse effects.
  3. Observe for signs of renal, hepatic or haematological dysfunction during prolonged therapy.
  4. Observe for signs of super-infection.



  • Store at room temperature until reconstitution.
  • Should be used within 1 hour following reconstitution and is not suitable for storage.


  • Store at room temperature until reconstitution
  • Store in a refrigerator (2-8 °C) after reconstitution. Do not freeze.
  • Expires 14 days after reconstitution


  1. Edmund Hey (2011) Neonatal Formulary 6th Ed, page 111.
  2. Douglas Pharmaceuticals Ltd. Flucloxacillin powder injection data sheet. 18 May 2017. (accessed 26 October 2017)
  3. AFT Pharmaceuticals Ltd. Flucloxacillin capsules and powder for oral solution data sheet. 3 July 2017. (accessed 26 October 2017)
  4. Pullen J. et al. (2006) Population Pharmacokinetics and Dosing of Flucloxacillin in Preterm and Term Neonates, Ther Drug Monit 28:351-358
  5. Pacifici GM. et al. (2008) Clinical Pharmacokinetics of Penicillins in the Neonate: a review of the literature, European Journal of Clinical Pharmacology, 65; 191-198
  6. Pullen J. et al. (2007) Protein Binding of Flucloxacillin in Neonates, Ther Drug Monit, 29:279-283
  7. Herngren L. et al. (1987) Pharmacokinetics of Free and Total Flucloxacillin in Newborn Infants, European Journal of Clinical Pharmacology, 32; 403-409
  8. Neonatal Medicines Formulary Consensus Group. Flucloxacillin guideline. 10 August 2017

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Document Control

  • Date last published: 31 January 2018
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology, Paediatric Infectious Diseases
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years