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Acute lower urinary tract infection in an immunosuppressed non-pregnant woman receiving methotrexate — MSRA MC

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Hardall topics relevant for this examAcute lower urinary tract infection in an immunosuppressed non-pregnant woman receiving methotrexateMSRA

A 46-year-old woman contacts her GP with a 36-hour history of dysuria, urinary frequency and suprapubic pain. She has no vaginal discharge, fever, rigors, flank pain, nausea or vomiting. She is haemodynamically stable and is not pregnant. She has rheumatoid arthritis treated with methotrexate 20 mg once weekly, folic acid and adalimumab. Her eGFR is 56 mL/min/1.73 m². A midstream urine specimen has been sent for culture because she is immunosuppressed. She has not received antibiotics within the previous 3 months. Her previous urine culture grew Escherichia coli susceptible to nitrofurantoin, trimethoprim and pivmecillinam. What is the most appropriate immediate antimicrobial prescription?

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Correct answer: C — Prescribe nitrofurantoin modified-release 100 mg twice daily for 3 days

She has a symptomatic lower UTI, with dysuria, frequency and suprapubic pain but no systemic features suggesting pyelonephritis or sepsis. NICE permits either immediate or back-up antibiotics for non-pregnant women, but immunosuppression increases the risk of complications; in this context, immediate treatment is the better strategy while culture is pending. Nitrofurantoin is an appropriate first-choice antibiotic because her eGFR is above the NICE threshold of 45 mL/minute and the recommended course for non-pregnant women is 100 mg modified-release twice daily for 3 days. The urine culture should be reviewed when available, changing therapy if the organism is resistant and she is not already improving. A back-up prescription is plausible in otherwise low-risk non-pregnant women, but is less appropriate here because of immunosuppression. Trimethoprim would ordinarily be a first-choice option when resistance risk is low, but it should be avoided with methotrexate because of potentially severe, sometimes delayed bone-marrow suppression. Pivmecillinam is a second-choice agent when a first-choice option is unsuitable or ineffective. A 7-day nitrofurantoin course is not routinely indicated for a non-pregnant woman; immunosuppression supports prompt treatment rather than automatically prolonging treatment duration.

Reference: NICE NG109: Urinary tract infection (lower): antimicrobial prescribing — Recommendations (31 October 2018) — https://www.nice.org.uk/guidance/ng109/chapter/Recommendations NHS Specialist Pharmacy Service: Managing interactions with methotrexate (Last updated 30 June 2025) — https://www.sps.nhs.uk/articles/managing-interactions-with-methotrexate/ NICE NG109: Urinary tract infection (lower): antimicrobial prescribing — Summary of the evidence (31 October 2018) — https://www.nice.org.uk/guidance/ng109/chapter/summary-of-the-evidence