Should a patient with a urinary tract infection (UTI) and yeast growth in urine culture, currently on cefdinir (Cefdinir), be treated with fluconazole?

From the Guidelines

Yes, fluconazole should be prescribed for this patient since the urine culture grew yeast and cefdinir (an antibiotic) will not treat a fungal infection. The recommended dosing for uncomplicated fungal urinary tract infection is fluconazole 200 mg orally on the first day, followed by 100 mg daily for 7-14 days total, as supported by the 2016 update by the Infectious Diseases Society of America 1. For patients with normal renal function, no dose adjustment is needed. The cefdinir should be discontinued as it is ineffective against yeast and may contribute to further fungal overgrowth. Before starting treatment, it's essential to remove any urinary catheters if present, as they can serve as a nidus for infection. Fluconazole works by inhibiting fungal cytochrome P450 enzyme 14α-demethylase, which prevents the conversion of lanosterol to ergosterol, an essential component of the fungal cell membrane. This mechanism makes it effective against most Candida species, which are the most common yeasts found in urinary tract infections. Patients should be advised to complete the full course of treatment even if symptoms improve before completion. It's also important to note that fluconazole is the drug of choice for treating Candida UTI, as it achieves high concentrations in the urine and is effective in eradicating candiduria, as shown in a randomized, double-blind, placebo-controlled trial 1. In contrast, other antifungal agents, such as flucytosine and amphotericin B, may be considered for fluconazole-resistant organisms or specific cases, but fluconazole remains the first-line treatment for uncomplicated Candida UTI. The 2009 guidelines also support the use of fluconazole for symptomatic candiduria, with a recommended dosage of 200 mg daily for 2 weeks for cystitis due to fluconazole-susceptible Candida species 1. However, the 2016 update provides more recent and comprehensive guidance on the management of Candida UTI, making it the preferred reference for treatment decisions.

From the FDA Drug Label

Fluconazole tablets are indicated for the treatment of: ... Candida urinary tract infections... The patient has a urine culture that grew yeast, which suggests a Candida urinary tract infection.

• The patient should be treated with an antifungal medication.
• Fluconazole is indicated for the treatment of Candida urinary tract infections.
• The dosing of fluconazole for this indication is not specified in the provided drug label, therefore no recommendation can be made. 2

From the Research

Urine Culture and Antifungal Treatment

• The patient's urine culture grew yeast, and they were placed on cefdinir for a UTI 3.
• However, cefdinir is an antibiotic and will not be effective against yeast infections.
• The presence of yeast in the urine may indicate a Candida urinary tract infection (UTI), which can be caused by hematogenous spread or retrograde route via the urethra 3.

Indications for Antifungal Therapy

• Antifungal therapy is not warranted in asymptomatic patients, except in cases of neutropenia, very low-birth-weight infants, or patients undergoing urologic procedures 3, 4.
• Since the patient is symptomatic, antifungal therapy may be necessary.

Choice of Antifungal Agent

• Fluconazole is the treatment of choice for symptomatic Candida UTIs, as it achieves high urinary levels 3, 4.
• Amphotericin B deoxycholate is an alternative antifungal agent if fluconazole cannot be used due to resistance, allergy, or failure 3.
• Other azole antifungals and echinocandins do not reach sufficient urine levels and are not recommended for the treatment of UTIs 3, 4.

Dosing of Fluconazole

• A fluconazole 200-mg loading dose followed by 100 mg/d for at least four days appears to be an appropriate dose for the treatment of symptomatic candidal UTI in patients without systemic fungal infection or severe renal failure 5.
• However, the optimal dosing of fluconazole may vary depending on the specific circumstances of the patient, and further studies are needed to determine the most effective dose 5.

Considerations for Treatment

• The patient's renal function should be considered when choosing an antifungal agent, as some agents may not be suitable for patients with renal dysfunction 6.
• Amphotericin B bladder irrigations may be an alternative treatment option for patients with renal dysfunction or those who do not respond to fluconazole 6.