A new class of drugs slashes the number of hot flashes in menopausal women by almost three-fourths in only three days. The new treatment, which was tested at Imperial College London, also reduced the severity of hot flashes by a third.

The study was a randomized, double-blind, placebo-controlled trial, involved 37 menopausal women aged between 40 and 62 years old who experienced seven or more hot flashes a day.

Volunteers were randomly chosen to first receive either an 80mg daily dose of the drug, called MLE4901, or a placebo over a four-week period. At the end of four weeks, they were switched to receive the other tablet for another four weeks.

The procedure ensured the women acted as their own controls, and the effects of the drug were clear.

The researchers found that the compound MLE4901 significantly reduced the average total number of hot flashes during the four-week treatment period, as well as their severity, compared to when the patients received the placebo for four weeks.

The compound won't be the subject of additional trials due to side effects that may affect liver function. However, two very similar drugs which don't appear to cause the same side effects are now undergoing trials.

The new experimental compounds are thought to work by blocking the action of a brain chemical called neurokinin B (NKB). Previous animal and human trials have shown increased levels of NKB may trigger hot flashes. The drug compound is thought to prevent NKB from activating temperature control areas within the brain — which appears to stop hot flashes.  

The study of MLE4901 also found that it was as effective at improving daytime symptoms as it was at symptoms that occurred at night. Furthermore, the women reported an 82 percent decrease in the amount their hot flashes interrupted their sleep, and a 77 percent reduction in interruption to their concentration.

"To see the lives of our participants change so dramatically and so quickly was so exciting, and suggests great promise for the future of this new type of treatment," said first author Dr. Julia Prague.

The researchers hope the new type of drug may provide women an alternative to using hormone replacement therapy (HRT), which contains estrogen and may increase the risk of breast cancer and blood clots.

The study was published in the journal Menopause.