What are the recommended first-line antibiotics for treating uncomplicated pyelonephritis in adults?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

Recommended first-line antibiotics for treating uncomplicated pyelonephritis in adults:

  • Trimethoprim 200 mg twice daily for 14 days, but only if appropriate based on culture and sensitivity results.
  • Ciprofloxacin 500 mg twice daily for 7 days; however, systemic fluoroquinolones like ciprofloxacin should only be prescribed when other commonly recommended antibiotics are inappropriate due to their potential for serious side effects.
  • For pregnant women who do not require admission, cefalexin 500 mg two or three times daily (up to 1–1.5 g three or four times daily for severe infections) for 7–10 days is recommended.

Fluoroquinolones should be reserved for cases where first-line antibiotics are contraindicated, have caused adverse effects, or resistance is present. Analgesia with paracetamol (and possibly low-dose codeine) is advised, while NSAIDs are not recommended due to renal safety concerns.

It is important to review culture and sensitivity results when available and adjust antibiotics accordingly. If symptoms worsen or do not improve within 48 hours, reassessment and possible referral are advised.

References:

Educational content only. Always verify information and use clinical judgement.