Inspections carried out by the health department found five products containing Sildenafil, one of the main ingredients of Viagra.

The adulterated items had names like Dragon Power and King 100% Natural Male Tonic.

Dr Mike Mawhinney, who carried out the , said anyone concerned should contact their GP or pharmacist.

He said drugs like Viagra “should only be given on prescription”.

“The department would advise them to… bring the product along with them, explain that they have taken them, explain that they have learned that they may be adulterated,” he said.

“Their GP or pharmacist will know what to do.”

Traditional medicines have been used for centuries

At the moment there is nothing to prevent anyone setting up a Chinese medicine shop, so reputable practitioners are calling for the profession to be regulated.

Dr Rifang How, a member of the British Register of Chinese Medicines, said that until there was regulation, patients should check that their practitioner is suitably qualified.

“For patients, it is very essential to go the qualified practitioner and after having a full , get the herbs or products from approved suppliers,” she said.

“Patients should be very confident with all the products they have got and confident with the service they have got.”

‘Element of emotion’

However, Dr Hugh McGavock, a pharmacologist, is against people taking any kind of herbal medicine.

“They are impure, they are unstandardised - you can’t be sure of the dosage from one batch to the next, they have multiple plant chemicals in them,” he said.

“They are not just pure, natural substances and they mostly have a very, very low…. effectiveness. So you are actually paying to get almost nothing.

“There is a huge element of emotion in this. It’s what doctors call the placebo effect. All medicines, if given with enough enthusiasm will do you good, even if there’s almost nothing in them.

“”My general advice would be if you want magic, go to a magician. If you want medicine go to a doctor or a pharmacist.”

BBC Northern Ireland health correspondent Dot Kirby said: “Chinese medicine has been around for 2,000 years.

“Now practitioners are tarnishing its reputation. The regulation of the components of herbal medicines is already tightening.

“Some hope that the regulation of the actual practitioners is not far behind.”

US found an increased risk in men with a history of heart attack or high blood pressure.

The University of Alabama team said healthcare professionals should warn patients of the potential risk.

The British Journal of Ophthalmology study follows several reports linking the drugs to eyesight problems.

NAION A common cause of sudden vision loss in people over 50 Caused by a blockage of the tiny ciliary arteries supplying blood to the anterior optic nerve There is no direct treatment, although corticosteroids are sometimes used to reduce swelling in the optic nerve

The findings are based on 76 men attending one US specialist eye clinic.

Half the men had optic nerve damage, diagnosed as anterior ischaemic optic neuropathy (NAION), the rest were free of the problem.

All the patients were asked about their lifestyle, including smoking and alcohol intake, whether they had been diagnosed with heart disease, diabetes, or high blood pressure and prescribed treatment for these conditions.

They were also asked if they had been prescribed Viagra and Cialis for erectile difficulties.

Men with optic nerve damage were no more likely to have taken the impotency drugs than men in the comparison group.

But men who had had a heart attack were 10 times more likely to have optic nerve damage if they had taken Viagra or Cialis before their diagnosis.

Men with high blood pressure were also more likely to have optic nerve damage if they had taken these drugs, although this was not significant.

Blood flow

The authors caution that their study is small, but suggest that the drugs may reduce the blood flow to the anterior optic nerve, resulting in tissue damage.

They believe the drugs may heighten the risk of NAION in those with vascular disease, who are already more .

The researchers urge any patient who has endured a sudden severe loss of vision, and has been prescribed Viagra or Cialis, to contact a doctor.

Writing in the journal, they said: “Though NAION is a rare condition, the large number of men using Viagra or Cialis suggests that, should an association truly exist, the incidence of NAION could rise dramatically.”

An editorial in the same journal points out that some patients with impaired eyesight as a result of NAION have reportedly decided to sue Pfizer, the manufacturers of Viagra.

However, Pfizer has said there were no reports of NAION in the trials of the drug carried out before it was licensed.

The company also argued that a greater number of cases related to this type of drug would have been reported by now if the association was anything other than coincidental.

Lilly ICOS, which Cialis, said there had been a small number of cases of NAION in people taking the drug.

This was now flagged up in the prescribing information.

In a statement, the company said it was difficult to establish a firm link as most patients taking impotency drug had other risk factors which rendered them potentially vulnerable to NAION.

Ngai reached new levels of excitement when his horse, Lovely, claimed two wins in the province during June, before Southern Hope kept the momentum going with another victory.

But it was later urine samples taken from the pair - who both ran on the Flat - contained the banned substance , which is the main derivative of Viagra.

In a statement, the Macau Jockey Club said Sildenafil was “a human preparation which had no legitimate use in a racehorse”.

The concluded: “It would also have an action on the cardiovascular, nervous and reproductive systems of a racehorse and as such was a prohibited substance.”

Ngai admitted the charges and was fined a total of HK$300,000 (25,000), along with the .

His appeal against the penalty will be heard on Saturday, when he expects to have a solid each-way chance.

Levitra, the first market rival to the hugely profitable Viagra, is being manufactured by the German firm, Bayer AG, and marketed by the British firm GlaxoSmithKline (GSK) as an alternative oral therapy for erectile dysfunction.

Since its in 1998, sales of Pfizer’s Viagra have risen to nearly $2bn a year.

Both pills work in the same manner and doctors warn that both can have serious side effects, especially for men with heart problems.

A third pill, Cialis, is expected to reach the US market later this year.

The US Food and Drug Administration (FDA) approved Levitra, an orange pill compared to Viagra’s blue, based on studies showing that men were on average five times more likely to achieve an erection suitable for when taking the pill compared with those given a dummy medicine.

Researchers reported that studies of several thousand men showed that Viagra helped more than 70% improve their
erections.

As well as the warnings to men with heart conditions, the FDA said Levitra was not for patients with who had suffered a recent heart attack or stroke who have very low blood pressure or uncontrolled high blood pressure.

For otherwise healthy men, Levitra’s main side effects
were headache, flushing and a stuffy nose and sometimes dizziness.

Lawson Macartney, head of strategic management of GlaxoSmithKline’s cardiovascular, metabolic and urology drugs, said: “We know, from considerable market research, that the
market is ready for new options”.

GSK expects Levitra to be available in September.

Allen Valentine’s business in Wembley, with a warehouse in Watford, could produce 500,000 tablets a day.

Harrow Crown Court heard on Friday the operation was “one of the largest illegal drug and pharmaceutical production operations in Europe”.

Valentine, 44, from Harrow, who admitted supplying class C drugs, was jailed for five-and-a-half years.

The court heard Valentine’s “” international operation, which also churned out steroids and cartons of potentially dangerous pills, risked the health of the public and is believed to have made him millions.

Viagra and diazepam are no longer the subject of jokes. They are for many people the to restore normality to the value of living. Judge Barrington Black

Just 24 hours before he was arrested, the father-of-two offered 1.25m cash for a palatial mansion in one of the country’s most sought-after areas and arranged delivery of a new 26,500 Jeep Cherokee.

Valentine, of Kynaston Wood, pleaded guilty to conspiracy to supply Class C drugs between January 1, 2001 and April 21 this year, as well as two similar charges involving contraventions of the Trade Marks Act and
Medicines Act.

Passing sentence Judge Barrington Black told the drugs producer, a former sales rep for Viagra maker Pfizer, that he had traded on people’s need for a “normal life”.

‘Serious matter’

He said “considerable” sums were invested by pharmaceutical companies to develop products in a “controlled and safe” way.

“It is a serious matter when the public are hoodwinked to the extent that such products, although akin to the correct ones, are being produced in an environment without the necessary precautions… in a makeshift and potentially dangerous manner.

“Viagra and diazepam are no longer the subject of jokes. They are for many people the constituents to restore normality to the value of living.”

Also imprisoned was Davin Pattni, 27, of Beverley Gardens, Stanmore, Middlesex, who got three years after pleading guilty to two of the conspiracy counts.

A third defendant, Paul Austin, 40, of Hampden Road, Harrow - regarded by police as a low level “gopher” - received an 18-month sentence suspended for two years for one of the conspiracy charges he had admitted.