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Dose and administration 

Suspected Sepsis:11,12

Dose  Postnatal Age (days) Dosing Interval (hr)
50mg/kg 0 to 7 12
>7 8
>28 days post term 6 hourly
Refer to SSH Meningitis Guideline


  • Empirical therapy for infants with risk factors for sepsis or suspected sepsis. Usually administered in combination with gentamicin, cefotaxime
  • Specific therapy for Streptococcus agalactiae (Group B streptococcus), Listeria monocytogenes


Hypersensitivity to penicillins/cephalosporins.


  • Caution in preterm infants, especially extreme immaturity.
  • Caution in infants with renal impairment - reduce dose
  • Caution in infants with gastrointestinal disease.

Clinical pharmacology

Amoxicillin is a broad spectrum penicillin with antibacterial activity against certain gram negative and gram positive organisms.  It is in activated by penicillinases including those produced by Staphylococcus aureus, E.coli, Pseudomonas, Klebsiella, and Enterobacter.6

Widely distributed at varying concentrations in human body tissues and fluids.  Very little passes into the CSF unless the meninges are inflamed.  Low binding to human plasma protein.  Half-life (adults) of 1 to 1.5 hours, which would be extended in the neonate.7  Excreted mainly unchanged by the kidneys.

Possible adverse effects

  • Venous irritation, soft tissue injury at site of IV injection.
  • Crystalluria - may be associated with reduced urine output
  • Gastrointestinal disturbance (diarrhoea)
  • Hypersensitivity reactions (including urticaria, fever, joint pains, rash, angioedema, anaphylaxis, serum sickness-like reaction (discontinue treatment).
  • CNS toxicity including convulsions (with high doses or in severe renal impairment)

Special considerations

  • May give concurrently with aminoglycoside therapy for synergistic effect.
  • Administer amoxicillin separately from aminoglycosides as simultaneous administration may cause inactivation.
  • Maintain adequate fluid intake and urinary output during administration of high doses, to avoid crystalluria.

Management of Amoxicillin administration


  • White to cream powder which, on reconstitution, may be red initially turning rapidly to a clear, pale yellow colour.
  • Available as vials of 250 mg, 500mg and 1 g.
  • A 10% solution ( 100mg in 1 mL) has pH 8-10


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


Slow IV Injection12,14,15

Reconstitute with Water for Injection to 100 mg/ml immediately prior to use.

  Amoxicillin 250mg Amoxicillin 500mg
Powder Space  0.2ml 0.4ml
Water to be added 2.3ml 4.6ml
  100mg in 1.0ml 100mg in 1.0ml
  1. Shake vigorously. Use immediately after reconstitution.
  2. Filter before administration through a 0.2 micron Pall filter.
  3. Administer by slow IV injection over 3-5 minutes.
  4. Compatible with sodium chloride 0.9%, glucose 5% (the preferred diluent is sodium chloride 0.9% as the solution is more stable) . However must be used immediately after reconstitution, especially if glucose 5 % is used as the diluent.
  5. Do NOT mix with other drugs, IV solutions, blood or blood products.
  6. Flush line with sodium chloride 0.9% before and after infusion of amoxicillin
  7. Keep patient well hydrated to avoid the possibility of amoxicillin crystalluria.

Nursing considerations

  • Observe for signs of adverse effects.
  • Observe IV site carefully during administration.
  • Observe for signs of renal,or haematological dysfunction during prolonged therapy.


  • Store at room temperature <25°C until reconstitution.
  • Use immediately following reconstitution.
  • Do not store following reconstitution.


  1. Prober CG, Stevenson DK, Benitz E. The use of antibiotics in neonates weighing less than 1200 grams. Pediatr Infect Dis J 1990; 9:111
  2. Kaplan JM, McCracken GH, Horton LJ, et al: Pharmacologic studies in neonates given large dosages of ampicillin. J Pediatr 1974; 84:571.
  3. Axline SG, Yaffe SJ, Simon HJ: Clinical pharmacology of antimicrobials in premature infants: II. Ampicillin, methicillin, oxacillin, neomycin, and colistin. Pediatrics 1967; 39:97.
  4. Young TE, Magnum OB, Neofax. A manual of drugs used in neonatal care. 10th Edition 1997, p8-9.
  5. The Northern Neonatal Network Neonatal Formulary. BMJ Books 2nd Edition 1998, p47.
  6. Mehta DK (ed).  British National Formulary (BNF 39; March 2000).  London: British Medical Association and the Royal Pharmaceutical Society, 2000.
  7. Reynolds JEF (ed).  Martindale: The Extra Pharmacopoeia (31st edition).  Royal Pharmaceutical Society, 1996: London
  8. Charles BG, Preechagoon Y, Lee TC, Steer PA, Flenady V, Debuse N.  Population pharmacokinetics of intravenous amoxycillin in very low birth weight infants.  J Pharmac Sciences 1997; 86(11):1288-92.
  9. Huisman-de Boer J, Van den Anken J, Vogel M, Goessens W, Schoemaker RC, Groot R.  Amoxicillin pharmacokinetics in preterm infants with gestational ages of less than 32 weeks.  Antimicrobial Agents and Chemotherapy 1995; 39:431-4.
  10. Starship Clinical Guidelines/Meningitis/June 2016
  11. New Zealand Formulary (NZF). NZF v[50]. [2016]. Available from: (Accessed [August], [2016])
  12. Ibiamox (amoxycillin) [New Zealand data sheet]. Douglas Pharmaceuticals Ltd [updated 6/10/2011]. Available from URL:
  13. Sutherland J, Ponen S, Wilson S (eds). [Amoxicillin] Notes on Injectable Drugs, 7th edition. New Zealand Hospital Pharmacists' Association Inc, Wellington, 2015Australian Injectable Drugs Handbook (6th ed.). Victoria, Australia: The Society of Hospital Pharmacists of Australia, 2014.
  14. McEvoy G (ed.). Handbook on Injectable Drugs (18th ed.). Bethesda: American Society of Health-System Pharmacists, Inc,2015.

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Document Control

  • Date last published: 24 August 2016
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology, Paediatric Infectious Diseases
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years