Introduction

Recurrent urinary tract infection (UTI) in women is quite common, and antimicrobial resistance makes treatment of recurrent UTIs even more challenging. In Norway, the prevalence of recurrent UTI is upto 30% in women aged >40 years and methenamine hippurate has accounted for 20% of the total antibiotic prescribing in 2015, as measured in defined daily dosages (DDDs). Methenamine has been prescribed for many years for prevention of recurrent UTI but there are no studies which have demonstrated a significant preventive effect on long-term use.

Aim

To assess the efficacy of methenamine in prevention of recurrent UTI in women aged >40 years.

Method

Study Design

• Case-control study

Patient Profile

• Women aged ≥ 40 years with recurrent UTI, defined as ≥3 courses of UTI antibiotic/year within the 2-year observation time
• Use of methenamine >5 DDD/day per 2 years

Treatment Strategy

• Data for all antibiotics used for UTIs dispensed from all pharmacies from 2005 to 2015 were retrieved from the Norwegian prescription database (NorPD); all women given an antibiotic prescription (n=10,97,895)
• The duration of the study was 6 years (from July 2007 to June 2013); n=79,721; of which 17,608 were prescribed methenamine and 62,113 were not prescribed methenamine
• A methenamine-treated group was age-, year-, and antibiotic-use matched with controls
• Researchers compared UTI prescriptions two years before and after treatment initiation, analyzing regular users and separately assessing high-consumption methenamine users

Endpoints

• The numbers of UTI prescriptions during the 2 years before and after inclusion 

Results

• The annual prevalence for recurrent UTI was 2.4% in women ≥ 40 years
• The differences in the dispensation of antibiotics 2 years before inclusion and during 2 years of treatment of UTIs is shown in table 1.

Table 1. Difference in antibiotic prescriptions in methenamine users and control group

• A significant reduction of 44.9% and 34.6% in the number of UTI antibiotic prescriptions was seen in the methenamine and control groups, respectively
• Among the methenamine users with higher number of UTI antibiotic prescriptions (>5/year) before starting methenamine, a greater reduction of 58.1% was seen in UTI antibiotic prescriptions

Conclusion

• Methenamine has a significant preventive effect in women aged >40 years with a history of recurrent urinary tract infection for >2 years.

Scand J Prim Health Care, 2022, 40(3), 331–338.   Doi:10.1080/02813432.2022.2139363.