ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Penicillin-Class Antibiotic (Amidinopenicillin) Pregnancy: Use with caution in pregnancy — safety data limited; prefer nitrofurantoin (avoid at term) or cefalexin in pregnancy

Pivmecillinam

Brand names: Selexid

Adult dose

Dose: 400 mg three times daily for 3 days (uncomplicated lower UTI in women)
Route: Oral
Frequency: Three times daily
Max: 1200 mg/day
NICE NG109: Recommended as first-line option for uncomplicated lower UTI in women (alongside nitrofurantoin and trimethoprim) to preserve antibiotic stewardship

Paediatric dose

Dose: Seek specialist opinion N/A/kg
Route: Oral
Frequency: Seek specialist opinion
Max: Seek specialist opinion
Seek specialist opinion

Dose adjustments

Renal

No dose adjustment required for mild-moderate renal impairment; use with caution if eGFR under 10

Hepatic

Use with caution in hepatic impairment

Paediatric weight-based calculator

Seek specialist opinion

Clinical pearls

  • NICE NG109 first-line for uncomplicated lower UTI in women — nitrofurantoin, pivmecillinam, or trimethoprim (based on local resistance patterns); pivmecillinam preferred where nitrofurantoin resistance common
  • Unique mechanism: targets penicillin-binding protein 2 (PBP2) — different target from standard penicillins, so resistance patterns differ; active against many E. coli strains resistant to other antibiotics
  • Must be taken with adequate fluid (at least 100 mL) and patient should remain upright for 30 minutes — oesophageal ulceration reported with inadequate fluid intake
  • Not effective for upper UTI (pyelonephritis) or complicated UTI — limited tissue penetration
  • Depletes carnitine with prolonged use — avoid long courses; not for prophylaxis

Contraindications

  • Hypersensitivity to penicillins or cephalosporins
  • Oesophageal strictures (tablet must be swallowed with adequate fluid — risk of oesophageal ulceration)
  • Carnitine deficiency

Side effects

  • GI upset (nausea, diarrhoea)
  • Oesophageal ulceration (if inadequate fluid with tablet)
  • Hypersensitivity reactions
  • Candidal superinfection

Interactions

  • Warfarin (enhanced anticoagulant effect)
  • Methotrexate (increased methotrexate levels)
  • Oral contraceptives (theoretical reduced efficacy — additional contraception for 7 days)

Monitoring

  • Symptom resolution within 48-72 hours
  • Urine culture if symptoms persist

Reference: BNFc; BNF 90; NICE NG109 (UTI in adults); PHE Antimicrobial Prescribing Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways