Published: 4 June 2020


Flucloxacillin – sometimes bad news for kidneys

Prescriber Update 41(2): 37
June 2020

Key Messages

  • Flucloxacillin is a very rare cause of interstitial nephritis.
  • Early recognition and prompt treatment results in better outcomes.

Flucloxacillin can injure the kidneys as well as the liver. Both interstitial nephritis and hepatitis are listed as very rare undesirable effects in the flucloxacillin data sheets1,2. However, in the last five years (1 January 2015 to 31 December 2019) the Centre for Adverse Reactions Monitoring (CARM) has received 39 reports of liver-related reactions and 13 reports of kidney-related reactions. These reports suggest interstitial nephritis may be an under-recognised reaction to flucloxacillin.

Of the 13 reports of renal reactions, the majority occurred in patients aged over 70 years. The median time to onset was three days, and the longest reported onset time was 20 days. Where the information was provided, two patients were reported to have died, three patients had recovered, and the majority (seven) had not yet recovered. Early recognition of flucloxacillin-induced interstitial nephritis and prompt treatment reduces the risk of long-term renal impairment3.


  1. AFT Pharmaceuticals Limited. 2019. Flucloxacillin (AFT) New Zealand Data Sheet 5 August 2019. URL: (accessed 21 April 2020).
  2. Mylan New Zealand Ltd. 2018. Staphlex New Zealand Data Sheet 23 July 2018. URL: (accessed 21 April 2020).
  3. Medsafe. 2015. Keeping it renal: Drug-induced acute interstitial nephritis. Prescriber Update 36(2): 26. URL: (accessed 21 April 2020).
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