October 2, 2022

An alternative to antibiotics can prevent recurrent UTIs

Methenamine is a long-established drug that works by making urine more acidic and stopping bacterial growth. Photo by chuckstock/Shutterstock

Women with frequent UTIs often take antibiotics daily to ward them off. But an old alternative to antibiotics could work just as well, according to a new clinical trial.

The researchers found that the drug, called methenamine, was comparable to standard low-dose antibiotics in preventing recurrent UTIs in women. Either treatment reduced infections to about one per year, on average.

Methenamine is a long-established drug that works by making urine more acidic and stopping bacterial growth. Studies have shown it can prevent recurrent UTIs, but it’s not widely used.

It’s such an “old” drug that many doctors today don’t 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 to prevent recurrent UTIs, favoring methenamine instead.

A concern with daily antibiotic use is diet antibiotic resistance, where the bacteria learn to counteract the drugs used to kill them. Plus, says Eilber, it upsets the body’s normal bacterial balance.

Dr Chris Harding, consultant urological surgeon at Freeman Hospital in the UK, led the trial.

He said this “adds evidence to support the use of methenamine and will be particularly welcome for women with recurrent UTIs who wish to avoid long-term antibiotic treatment.”

UTI are extremely common and can affect anyone, but are especially common in women. Studies suggest that up to 80% of women develop a UTI at some point, and about a quarter of these women have frequent recurrences.

Some symptoms include burning during urination and a strong, persistent urge to urinate.

The new study — recently published online in the BMJ — involved 240 women with recurrent UTIs. At first, they averaged about six UTIs a year.

Half of the women were randomly assigned to daily low-dose antibiotic treatment, while the other half took methenamine twice daily.

Over the course of a year of treatment, both groups saw a significant drop in UI episodes. Women in the antibiotic group averaged just under one episode per person over the year, while those taking methenamine had just over one episode per person.

It’s a small difference, Harding said, and one that, based on patient focus groups, wouldn’t be considered “clinically significant.”

As for side effects, a small number of women in each group reported issues such as nausea, abdominal pain, and diarrhea. Six women developed a urinary tract infection with fever and four required hospitalization – all in the methenamine group.

Whether treating more UTIs with methenamine will help tackle the problem of antibiotic resistance is an open question. Over the 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 took methenamine had more antibiotic-resistant bugs.

Harding said the finding “should be interpreted with caution” because the trial was not primarily intended to assess antibiotic resistance.

“Further research is definitely indicated in this area,” he said.

For now, women should know that there are options to prevent frequent UTIs, 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 sexual intercourse. (Sexual activity can encourage bacteria that cause UTIs to move into the urethra, the tube that releases urine from the body.)

For postmenopausal women, Eilber said, vaginal estrogen can help prevent recurrent UTIs. After menopause, the vaginal tissue changes in ways that promote the growth of “bad” bacteria.

Experts also usually advise certain self-care measures that can help, such as drinking plenty of water, urinating before and after sex, and wiping back and forth 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 by age. The study also did not include men. It is therefore unclear whether the results would apply to the elderly, another group at increased risk for recurrent UTIs.

The study was funded by the UK’s National Institute for Health Research.

More information

The US Office of Women’s Health has more on urinary tract infections.

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