The breakthrough has led to hope the therapy could eventually provide an alternative to expensive and dangerous Hormone Replacement Therapy for women of a certain age.
Professor Waljit Dhillo, from the Department of Medicine at Imperial College, London, said: “We already knew this compound could be a game-changer for menopausal women and get rid of three-quarters of their hot flushes in four weeks.
“But new analysis confirms the beneficial effect is obtained very quickly – within just three days.”
The findings come from in-depth analysis of data collected from a clinical trial initially published last year.
The original drug trial involved 37 menopausal women aged between 40 and 62 who experienced seven or more hot flushes a day.
They were randomly chosen to receive either an 80mg daily dose of the experimental drug, known as MLE4901, or a placebo over the course of four weeks.
They then switched to receive the other tablet for an additional four weeks.
Researchers found the compound significantly reduced the average total number of flushes during the four-week period, as well as their severity, compared to when they received the placebo over the same period.
But new analysis shows its magic works within 72 hours.
The compound is thought to work by blocking the action of a brain chemical called neurokinin B [NKB], increased levels of which are thought to trigger hot flushes.
The drug is thought to prevent NKB activating temperature control areas within the brain which appears to halt hot flushes.
Scientists say MLE4901 will not be taken further in trials, due to worries over side effects that may affect liver function, yet similar drugs also blocking NKB but which do not appear to carry side effects have now entered larger clinical trials.
New drugs could be available within years.
The menopause occurs when oestrogen levels plunge, typically between the ages of 45 to 55, and leads to periods stopping, the inability to have children naturally and a number of physical changes, including hot flushes and sweating.
The drug is thought to block the chemical in the brain that triggers hot flushes (GETTY)
“To see the lives of our participants change so dramatically and so quickly was so exciting”
Dr Julia Prague
Women often describe a hot flush as a creeping feeling of intense warmth that quickly spreads across the body and face “right up to your brow”. It typically lasts for several minutes.
Others say the warmth is similar to the sensation of being under a sun bed.
For millions of women they are more than an uncomfortable inconvenience. And for some, frequent severe episodes can lead to clothes and bed sheets drenched in sweat, as well as relentless waking from sleep which impacts their working, social and home lives.
The review by British experts, the findings of which appear in the journal Menopause, also showed MLE4901 was as effective at improving daytime flush symptoms as it was at improving night time symptoms.
Women reported a 82 per cent decrease in the amount their hot flushes interrupted their sleep and a 77 per cent reduction in interruption to their concentration.
Study author Dr Julia Prague said: “As NKB has many targets of action within the brain the potential for this drug class to really improve many of the symptoms of the menopause, such as hot flushes, difficulty sleeping, weight gain, and poor concentration, is huge.
“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.”
Scientists now say the compounds could provide women with an alternative to Hormone Replacement Therapy, the current treatment for symptoms of the menopause.
HRT, which contains oestrogen, may increase the relative risk of breast cancer and can increase the risk of blood clots, meaning many women cannot use it to relieve their menopausal symptoms.