Methenamine is a long-established medication that works by making the urine more acidic and stopping bacterial growth. Photo by chuck stock/Shutterstock
Women plagued by frequent urinary tract infections often take daily antibiotics to ward them off. But an old antibiotic alternative might work just as well, a new clinical trial finds.
Researchers found that the medication, called methenamine, was comparable to standard, low-dose antibiotics in preventing women’s recurrent urinary tract infections (UTIs). Either treatment curbed the infections to around one per year, on average.
Methenamine is a long-established medication that works by making the urine more acidic and stopping bacterial growth. Studies have shown that it can prevent recurrent UTIs, but it’s not widely used.
It’s such an “old” drug, many doctors today do not know about it, said Dr. Karyn Eilber, a urologist at Cedars-Sinai Medical Center in Los Angeles.
Eilber, who was not involved in the new study, said she reserves daily antibiotics as a last resort for preventing recurrent UTIs, favoring methenamine instead.
A concern with daily antibiotic use is feeding antibiotic resistance, where bacteria learn to thwart the medications used to kill them. Plus, Eilber said, it disrupts the body’s normal bacterial balance.
Dr. Chris Harding, a consultant urological surgeon at Freeman Hospital in the United Kingdom, led the trial.
He said it “adds supportive evidence for the use of methenamine and will be particularly welcome to those women with recurrent UTI who want to avoid long-term antibiotic treatment.”
UTIs are exceedingly common and can affect anyone, but are particularly prevalent among women. Studies suggest up to 80% of women develop a UTI at some point, and about one-quarter of those women go on to have frequent recurrences.
Some symptoms include burning during urination, and feeling a strong, persistent urge to urinate.
The new study — published online recently in the BMJ — involved 240 women with recurring UTIs. At the start, they were averaging around six UTIs per year.
Half of the women were randomly assigned to daily low-dose antibiotic treatment, while the other half took methenamine twice a day.
Over one year of treatment, both groups saw a significant decline in UTI episodes. Women in the antibiotic group averaged just under one bout per person for the year, while those taking methenamine had just over one episode per person.
That is a small difference, Harding said, and one that, based on patient focus groups, would not be considered “clinically meaningful.”
As for side effects, a small number of women in each group reported problems like nausea, abdominal pain and diarrhea. Six women developed a UTI with fever, and four needed to be hospitalized – all of whom were in the methenamine group.
Whether treating more UTIs with methenamine will help battle the problem of antibiotic resistance is an open question. During the one year of treatment in this trial, women on antibiotics were more likely to harbor bacteria resistant to at least one antibiotic. But that changed when their bacteria were sampled six months later: Those who had taken methenamine had more antibiotic-resistant bugs.
Harding said that finding “should be interpreted with caution,” since the trial was not primarily aimed at gauging antibiotic resistance.
“Further research is definitely indicated in this area,” he said.
For now, women should know there are options for preventing frequent UTIs, the experts said.
“Low-dose antibiotics should definitely not be the first line,” Eilber said.
Besides methenamine, another alternative is to take an antibiotic only after sex. (Sexual activity can encourage UTI-causing bacteria to move into the urethra, the tube that releases urine from the body.)
For postmenopausal women, Eilber said, vaginal estrogen may help prevent recurrent UTIs. After menopause, the vaginal tissue changes in ways that may foster the growth of “bad” bacteria.
Experts also generally advise some self-care steps that can help, like drinking plenty of water, urinating before and after sex, and wiping front to back after using the bathroom.
Many of the women in the current trial were going through or past menopause. But, Harding said, his team did not look at the effects of treatment according to age. Nor did the study include men. So it’s not clear whether the findings would apply to older adults, another group at increased risk of recurrent UTI.
The study was funded by the U.K. National Institute for Health Research.
The U.S. Office on Women’s Health has more on urinary tract infections.