Imipenem with cilastatin

How it works

Imipenem inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, while cilastatin inhibits the renal enzyme dehydropeptidase-I to prevent imipenem breakdown in the kidney and raise its urinary concentration.

Prescribing in practice

• It lowers the seizure threshold, so use with caution in patients with central nervous system disorders, renal impairment or a history of seizures.
• Cross-reactivity can occur in patients with severe beta-lactam hypersensitivity, and use should follow antimicrobial stewardship to preserve carbapenem activity.
• Dose adjustment is required in renal impairment; consult the SPC and current prescribing references for regimen and administration.

Monitoring

Monitor renal function to guide dosing, observe for seizures and signs of hypersensitivity, and review for superinfection including Clostridioides difficile during prolonged use.

Counselling the patient

• Report any twitching, confusion or fits during treatment without delay.
• Tell the team about any previous serious reaction to penicillins or other antibiotics.
• Report severe or persistent diarrhoea, which should be assessed before taking any anti-diarrhoeal.

Evidence & guidelines

Carbapenems such as imipenem with cilastatin are reserved for serious or resistant infections under antimicrobial stewardship, consistent with NICE and UK antimicrobial guidance.