Something for a long weekend, sir?

Scientists have developed a new longer lasting Viagra-type pill that can help men overcome impotence for up to three days with a single dose.

The new drug, tadalafil, is still in the experimental stage but is reported to enable men to have sex on demand for at least 36 hours after it is taken and in some cases even longer.

News of the "super-Viagra" was given at a medical conference in Orlando, Florida.

Dr Hartmut Porst, professor of urology at the University of Hamburg, said: "Some of my patients tell me that they are still able to perform sexual intercourse three days after taking one pill."

Viagra revolutionised treatment of male impotence when it was introduced four years ago, but is only effective in about one third of patients.

The new drug was tested on 1,300 men over a 12-week trial conducted by Duke University Medical Center in North Carolina. It helped about 40 per cent of those who had been unable to get results with Viagra.

It will be marketed under the name Cialis by Lilly ICOS and could be available next year. A second drug, vardenafil, has been shown to help other types of impotence.