From the FDA Drug Label
To reduce the development of drug-resistant bacteria and maintain the effectiveness of Methenamine Hippurate Tablets and other antibacterial drugs, Methenamine Hippurate Tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy.
The patient's new onset polyuria and nocturia without classic UTI symptoms, while on Hiprex, warrants further investigation to rule out a urinary tract infection.
- A urine dipstick or midstream urine (MSU) culture is recommended to determine if a UTI is present, as the patient's symptoms could be indicative of a low-grade or chronic infection.
- The FDA drug label for Hiprex emphasizes the importance of using the drug only when a bacterial infection is proven or strongly suspected, and recommends considering culture and susceptibility information when available 1.
- Given the patient's symptoms and the fact that they are already on Hiprex, it is prudent to conduct a urine dipstick or MSU culture to guide further treatment and prevent the development of drug-resistant bacteria 1.
From the Research
Yes, both a urine dipstick and midstream urine (MSU) culture are warranted in a patient on Hiprex (methenamine) presenting with new onset polyuria and nocturia, even without classic UTI symptoms. These tests are important because Hiprex can mask typical UTI symptoms while the infection persists. The dipstick provides immediate information about potential infection markers like leukocyte esterase and nitrites, though nitrite tests may be falsely negative in patients on methenamine 2. An MSU culture remains essential as it definitively identifies any causative organisms and their antibiotic sensitivities. It's worth noting that a recent study from 2023 found methenamine hippurate to be effective in extending the mean period between symptomatic episodes of urinary tract infections (UTIs), keeping the patient symptom- and infection-free, and reducing the number of UTI episodes 2. However, the new urinary symptoms could indicate either medication side effects, developing UTI despite prophylaxis, or an unrelated condition like diabetes. Proper sample collection is crucial - the midstream technique helps minimize contamination, and the sample should be processed within four hours of collection for accurate results. Additionally, a 2023 study highlighted the importance of considering menopausal status and recurrent UTIs when assessing UTI symptoms in women, as these factors can impact the presentation of UTI symptoms 3. Given the potential for breakthrough infections and the importance of accurate diagnosis, urine dipstick and MSU culture are necessary diagnostic tools in this scenario, as supported by the most recent and highest quality study available 2.