Premature ejaculation can be distressing for couples
A spray can help men with premature ejaculation problems prolong the length of time they have sex by six times.
Men who used the treatment five minutes before having intercourse extended their love-making from half a minute to almost four minutes, trials showed.
The spray, developed at the Royal Victoria Hospital in Belfast, contains local anaesthetics that numb the penis.
A British Journal of Urology International study says it could be available in the next couple of years.
Up to 40% of men experience premature ejaculation at some time in their lives, experts estimate.
It is difficult to have an exact idea of the rate because there is still embarrassment about discussing sex lives and the definition of what constitutes a premature climax does vary.
For some 10 minutes in the sack may be enough, but for others intercourse lasting less than 20 minutes may be unsatisfactory.
In the study, the researchers looked at 300 men who regularly had difficulty lasting for more than a minute during love-making.
Most of the men had tried other treatments before, the most common being oral antidepressants.
Every time they had intercourse during the three-month study period, each couple measured the time to ejaculation with a stopwatch.
The men who tested the spray, called PSD502, were able to last 6.3 times longer on average.
In comparison, men who tested a "dummy" spray containing no drug lasted only 1.7 times longer.
PSD502 helped 90% of the men enjoy sex for up to four minutes, where they had previously only lasted for seconds.
And there was minimal transfer of the spray to the partners, meaning the men did not have to use a condom for this reason alone.
Lead researcher Professor Wallace Dinsmore said: "Premature ejaculation can be a very distressing condition for men and can cause distress, frustration and make them avoid sexual intimacy.
"Our study shows that when the PSD502 spray was applied to the man's penis five minutes before intercourse it improved both sexual performance and sexual satisfaction, which are key factors in treating premature ejaculation."
Peter Baker of the Men's Health Forum said the findings were welcomed.
"Premature ejaculation is a very significant problem for lots of men that is hardly talked about and that needs to change.
"There are treatments and training techniques that can help. It is important that new treatments are looked at and that men are encouraged to seek help."
Paula Hall, a counsellor for Relate, said: "This might particularly help men who have problems with premature ejaculation related to anxiety.
"It could help build their confidence, although the root cause of the anxiety would still need addressing."