In a 55‑year‑old man with normal renal function (estimated glomerular filtration rate ≥60 mL/min) who has candiduria and an uncomplicated bacterial urinary tract infection, can cefixime be co‑administered with fluconazole safely, and what are the recommended doses and monitoring?

Co-Administration of Cefixime and Fluconazole for Concurrent Bacterial UTI and Candiduria

Yes, cefixime and fluconazole can be safely co-administered in this patient with normal renal function, using cefixime 400 mg daily (divided into 200 mg twice daily for better tolerability) for the bacterial UTI and fluconazole 400 mg loading dose followed by 200 mg daily for 7-14 days for symptomatic candiduria. 1, 2, 3

Safety of Co-Administration

• There are no clinically significant drug interactions between cefixime and fluconazole that would preclude their concurrent use 2, 4
• Both medications can be administered orally, making outpatient management feasible 1, 2
• With normal renal function (eGFR ≥60 mL/min), no dose adjustments are required for either agent 5, 2

Cefixime Dosing for Bacterial UTI

• Administer cefixime 200 mg twice daily rather than 400 mg once daily to minimize gastrointestinal adverse effects, which are more common with single daily dosing 2
• Cefixime achieves adequate urinary concentrations with approximately 20% excreted as active drug in urine, making it effective for uncomplicated UTIs 2, 6
• Treatment duration is typically 7-10 days for uncomplicated cystitis or pyelonephritis 2, 6

Fluconazole Dosing for Candiduria

• The Infectious Diseases Society of America recommends fluconazole as the drug of choice for Candida UTI because it achieves high urinary concentrations and is available orally 1
• Use a loading dose of 400 mg on day 1, followed by 200 mg daily for 7-14 days for symptomatic candiduria or cystitis 1, 3, 7
• This dosing regimen is supported by the only randomized, double-blind, placebo-controlled trial demonstrating efficacy in eradicating candiduria 1

Critical Management Considerations

• Remove any indwelling urinary catheter immediately if present, as catheter removal alone resolves candiduria in approximately 50% of cases and significantly improves treatment success rates 1, 5, 7
• Confirm that candiduria represents true infection rather than colonization or contamination by obtaining a second urine culture if this is the first positive result 7
• Asymptomatic candiduria generally does not require treatment unless the patient has high-risk features (neutropenia, upcoming urologic procedures) 1, 5

Monitoring Parameters

• No specific laboratory monitoring is required for drug interactions between these agents in a patient with normal renal function 5, 2
• If the patient is on warfarin, monitor INR closely as fluconazole potentiates warfarin's anticoagulant effect 5
• Clinical response should be evident within 3-5 days; lack of improvement warrants repeat cultures and consideration of resistant organisms (particularly C. glabrata or C. krusei) 1, 7

Important Caveats

• Fluconazole is ineffective against C. krusei (intrinsically resistant) and has reduced activity against C. glabrata 1, 7
• If cultures identify these resistant species, alternative therapy with amphotericin B deoxycholate (0.3-0.6 mg/kg daily) or flucytosine may be necessary 1, 5
• Echinocandins achieve minimal urinary concentrations and should not be used for isolated candiduria, though they are effective for candidemia with renal involvement 1, 8