(Adds background on therapy and hot flashes throughout, FDA comment in paragraph 4, company comment in paragraph 5)

May 12 (Reuters) - The U.S. Food and Drug Administration on Friday approved Japanese drugmaker Astellas Pharma Inc's oral drug Veozah for the treatment of hot flashes associated with menopause.

Hormonal changes during menopause make the body more sensitive to fluctuations in body temperature, causing so-called vasomotor symptoms, or hot flashes and night sweats.

An estimated 21 million women in the United States will have those symptoms by 2025, Astellas Head of BioPharma Development Marci English told Reuters ahead of the approval.

"Hot flashes as a result of menopause can be a serious physical burden on women and impact their quality of life," said Janet Maynard, director at the FDA's office of rare diseases, pediatrics, urologic and reproductive medicine.

The drug's wholesale acquisition cost is $550 for a 30-day supply, and it is expected to be available in pharmacies within three weeks, Astellas said.

Hormone replacement therapy is currently used for treating vasomotor symptoms but it can increase the risk of breast cancer and blood clots.

The approval for Veozah, which is a non-hormonal treatment, was based on a late-stage study that showed it helped reduce the frequency and severity of vasomotor symptoms and improved patients' quality of life over the treatment period.

Use of anti-depressant paroxetine was the only FDA approved non-hormonal option available to patients until Veozah's approval.

Veozah carries a warning for higher liver enzymes or liver injury, with the FDA asking that people taking the pill be tested for liver damage or infection, with routine bloodwork done every three months for the first nine months of using the pill.

(Reporting by Raghav Mahobe and Aditya Samal in Bengaluru; Editing by Shounak Dasgupta and Vinay Dwivedi)