Acute Pyelonephritis / Upper Urinary Tract Infection (UTI)

Comments from the Expert Advisory Group

Send MSU for culture and sensitivity in all cases prior to the patient starting an antibiotic. Empirical antibiotic choice should be tailored based on previous results (if available).

Consider acute pyelonephritis/ upper urinary tract infection (UTI) when there is:

  • Flank pain which radiates to the iliac fossa and suprapubic area.
  • Sudden onset general systemic disturbance with fever, rigors, vomiting.
  • Tenderness and guarding over the kidney.
  • Nausea and/ or vomiting.

Consider referral to hospital in patients with pyelonephritis if:

  • Patient is significantly dehydrated or unable to take oral fluids and medicines.
  • Child/ young person <16 years with acute pyelonephritis.
  • Aged 16 years and over with acute pyelonephritis and has a severe systemic infection.
  • Patient is pregnant.
  • Patient has a higher risk of developing complications (e.g. people with known or suspected structural or functional abnormality of the genitourinary tract or underlying disease [such as diabetes or immunosuppression]).

Consider referral to secondary care for further investigation in:

  • Male patients, following a single episode of pyelonephritis without an obvious cause.
  • Female patients with recurrent pyelonephritis.

Nitrofurantoin is NOT a suitable antibiotic choice in pyelonephritis.


If no response within 24 hours consider referral to hospital
Drug Dose Duration Notes
1st Choice Option



500 mg every 8 hours (can increase to 1 g every 6 hours in severe infection)

7-10 days


Cephalosporins should not be used in severe penicillin allergy.


2nd Choice Options



500 mg every 12 hours


7 days


Multiple adverse effects associated with fluroroquinolones

Avoid ciprofloxacin in pregnancy.

Suitable in penicillin anaphylaxis.






625 mg every 8 hours




7-10 days




Avoid in penicillin allergy.

Use only when risk of resistance is low i.e. where previous culture suggests susceptibility (but co-amoxiclav was not used) or in younger patients without a significant antibiotic exposure history. Risk of resistance is more likely in older people in residential facilities.  

Patient Information

Safe Prescribing (visit the safe prescribing page)

Visit the Health Products Regulatory Authority (HPRA) website for detailed drug information (summary of product characteristics and patient information leaflets). Dosing details, contraindications and drug interactions can also be found in the Irish Medicines Formulary (IMF) or other reference sources such as British National Formulary (BNF) / BNF for children (BNFC).

Reviewed July 2023

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