Consultant urologist Ted McDermott has tested Viagra on Irish men over the past three years with some considerable success. The tests were carried out on 18 of his patients who suffer varying degrees of impotence. Mr McDermott is a consultant at the Meath and St James's Hospital in Dublin and the National Rehab in Dun Laoghaire.

At the beginning of the two-stage testing procedure, some patients were given a placebo and the others genuine Viagra. Those taking the new drug reported a marked improvement in their condition compared to the placebo.

At stage two, all the patients were given varying doses of Viagra.

"We were trying to ascertain, among other things, what was the most suitable dosage required in order to sustain an erection," Mr McDermott said yesterday.

The results among the 18 Irish men mirrored results worldwide. Given doses of 25mg, 60 per cent said they were satisfied with the results. This increased to a satisfaction rate of over 80 per cent when the dosage was raised to 100mg.

Three main side-effects were reported by some of the participants who experienced headaches and flushed skin. Ten per cent said it affected their sight - things took on a blue tint.

Two of the 18 experienced side-effects significant enough to make them drop out of the tests. "The others felt few or no side-effects. Most thought the occasional headache was worth it for the improvements it caused in their lives," said Mr McDermott.

The patients continue to be monitored by Mr McDermott. "A few of the patients are absolutely delighted. Their confidence has been restored. A very small minority of the patients were not able to get any type of erection before taking the drug," he said. While Viagra marks a breakthrough in impotence treatments, Mr McDermott stressed that the success of the drug depended on the individual.

"This is not the total answer. It is going to work for some and not for others. It is the first in a new line of drugs, and a lot more research is required to fully understand the physiology of erections," he said.

Mr McDermott said he had already received a large number of inquiries from the general public concerning the new treatment.

It is understood that Viagra will come on to the Irish market early next year but may be available before then.