New Nonhormonal Therapies for Hot Flashes on the Horizon

Tara Haelle

October 08, 2021

Hot flashes affect three out of four women and can last 7-10 years, but the current standard of care treatment isn't necessarily appropriate for all women who experience vasomotor symptoms, according to Stephanie Faubion, MD, MBA, director of the Mayo Clinic Women's Health Clinic in Jacksonville, Fla.

For the majority of women under age 60 who are within 10 years of menopause, hormone therapy currently remains the most effective management option for hot flashes where the benefits outweigh the risks, Faubion told attendees Sept. 25 during a plenary at the annual meeting of the North American Menopause Society. "But really, individualizing treatment is the goal, and there are some women who are going to need some other options."

Contraindications for hormone therapy include having a history of breast cancer, coronary heart disease, active liver disease, unexplained vaginal bleeding, high-risk endometrial cancer, transient ischemic attack, and a previous venous thromboembolic event or stroke.

"Fortunately, we have things in development," Faubion said. She reviewed a wide range of therapies that are not currently Food and Drug Administration approved for vasomotor symptoms but are either available off label or are in clinical trials.

One of these is oxybutynin, an antimuscarinic, anticholinergic agent currently used to treat overactive bladder and overactive sweating. In a 2016 trial, 73% of women taking 15 mg extended-release oxybutynin once daily rated their symptoms as "much better," compared with 26% who received placebo. The women experienced reduced frequency and severity of hot flashes and better sleep.

Subsequent research found a 60% reduction in hot flash frequency with 2.5 mg twice a day and a 77% reduction with 5 mg twice a day, compared with a 27% reduction with placebo. The only reported side effect that occurred more often with oxybutynin was dry mouth, but there were no significant differences in reasons for discontinuation between the treatment and placebo groups.

There are, however, some potential long-term cognitive effects from oxybutynin, Faubion said. Some research has shown an increased risk of dementia from oxybutynin and from an overall higher cumulative use of anticholinergics.

"There's some concern about that for long-term use," she said, but it's effective, it's "probably not harmful [when] used short term in women with significant, bothersome hot flashes who are unwilling or unable to use hormone therapy, and the adverse effects are tolerable for most women." Women with bladder symptoms would be especially ideal candidates since the drug already treats those.

Faubion then discussed a new estrogen called estetrol (E4), a naturally occurring estrogen with selection action in tissues that is produced by the fetal liver and crosses the placenta. It has a long half-life of 28-32 hours, and its potential mechanism may give it a different safety profile than estradiol (E2). "There may be a lower risk of drug-drug interactions; lower breast stimulation, pain or carcinogenic impact; lower impact on triglycerides; and a neutral impact on markers of coagulation," she said.

Though estetrol was recently approved as an oral contraceptive under the name Estelle, it's also under investigation as a postmenopausal regimen. Preliminary findings suggest it reduces vasomotor symptom severity by 44%, compared with 30% with placebo, at 15 mg, the apparent minimum effective dose. The safety profile showed no endometrial hyperplasia and no unexpected adverse events. In those taking 15 mg of estetrol, mean endometrial thickness increased from 2 to 6 mm but returned to baseline after progestin therapy.

"The 15-mg dose also positively influenced markers of bone turnover, increased HDL [cholesterol], improved glucose tolerance," and had no effects on coagulation parameters or triglycerides, Faubion added.

Another group of potential agents being studied for hot flashes are NK3 antagonists, which aim to exploit the recent discovery that kisspeptin, neurokinin B, and dynorphin (KNDy) neurons may play an important role in the etiology of vasomotor symptoDevelopment of one of these, MLE 4901, was halted despite a 45% reduction in hot flashes because 3 of 28 women developed transiently elevated liver function tests, about four to six times the upper limit of normal.

Two others, fezolinetant and NT-814, are in phase 2 trials and have shown a significant reduction in symptoms, compared with placebo. The most commonly reported adverse effect in the phase 2a trial was gastrointestinal effects, but none of the participants stopped the drug because of these, and no elevated liver tests occurred. In the larger phase 2b trial, the most commonly reported treatment-emergent adverse events included nausea, diarrhea, fatigue, urinary tract infection, sinusitis, upper respiratory infection, headache, and cough. Five women discontinued the drug because of elevated liver enzymes.

"Overall, NK3 inhibitors appear to be generally well tolerated," Faubion said. "There does seem to be mild transaminase elevation," though it's not yet known if this is an effect from this class of drugs as a whole. She noted that follicle-stimulating hormone does not significantly increase, which is important because elevated FSH is associated with poor bone health, nor does estradiol significantly increase, which is clinically relevant for women at high risk of breast cancer.

"We don't know the effects on the heart, the brain, the bone, mood, weight, or sexual health, so there's a lot that is still not known," Faubion said. "We still don't know about long-term safety and efficacy with these chemical compounds," but clinical trials of them are ongoing.

They "would be a welcome alternative to hormone therapy for those who can't or prefer not to use a hormonal option," Faubion said. "However, we may need broad education of clinicians to caution against widespread abandonment of hormone therapy, particularly in women with premature or early menopause."

Donna Klassen, LCSW, the cofounder of Let's Talk Menopause, asked whether any of these new therapies were being tested in women with breast cancer and whether anything was known about taking oxybutynin at the same time as letrozole.

"I suspect that most women with chronic diseases would have been excluded from these initial studies, but I can't speak to that," Faubion said, and she wasn't aware of any data related to taking oxybutynin and letrozole concurrently.

James Simon, MD, medical director and founder of IntimMedicine and one of those who led the research on oxybutynin, responded that his trials excluded breast cancer survivors and anyone taking aromatase inhibitors.

"It will be unlikely that, in the very near future, that data will be available because all the clinical developments on these NK3s or KNDy neuron-modulating drugs exclude cancer patients," Simon said.

However, another attendee, Lisa Larkin, MD, of Cincinnati, introduced herself as a breast cancer survivor who takes tamoxifen and said she feels "completely comfortable" prescribing oxybutynin to breast cancer survivors.

"In terms of side effects and effectiveness in patients on tamoxifen and aromatase inhibitors, I've had incredibly good luck with it, and I think it's underutilized," Larkin said. "The clinical pearl I would tell you is you can start really low, and the dry mouth really seems to improve with time." She added that patients should be informed that it takes 2 weeks before it begins working, but the side effects eventually go away. "It becomes very tolerable, so I just encourage all of you to consider it as another great option."

Faubion had no disclosures. Disclosure information was unavailable for Simon, Larkin, and Klassen.

This article originally appeared on, part of the Medscape Professional Network.


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