Next week marks the arrival of yet another sex enhancement product, Zestra. The arousal oil, based on botanical ingredients which, unlike many of the other products, claims to treat women with sexual dysfunction, will be available in Hong Kong next month.

The manufacturer of Zestra, QualiLife Pharmaceutical, has chosen Hong Kong for its Asian launch, some eight months after the product first hit the market in the US.

But while the enormous interest of the Hong Kong public in these products represents a fantastic opportunity for their manufacturers, others in the community worry that it is representative of an underlying sexual health problem among the city's 6.8 million people.

According to a market projection undertaken recently by Bayer Healthcare and GlaxoSmithKline, the pharmaceutical companies which jointly brought Levitra to Hong Kong a year ago, sales of male impotence drugs are expected to jump more than four-fold to about $69 million in 2007, from $16 million in 1999.

University of Hong Kong psychiatry professor Ng Man-lun, also known as a sexology expert, said sexual dysfunction affected about 50 per cent of married couples.

Professor Ng said impotence was the most common problem in men and accounted for about 70 per cent of dysfunction cases. Low sex drive also occurred in about half of all adults, and slightly more in females than in males. He also noted that as a general rule sexual satisfaction fell in line with age and the number of years of marriage. It was more pronounced in women.

But the problem was not Hong Kong's alone. Professor Ng said rates in the city were comparable to those in cities on the mainland and overseas.

He had his own theory on why the big drug companies had singled out Hong Kong as a prime market for their sex enhancement products. 'Chinese by tradition have a strong belief in herbal medicine. Yet the herbal products [in Hong Kong] are not as numerous or competitive as in mainland China,' he said.

'Also, the product can be sold at a higher price in Hong Kong than it can be in China, so that makes it a good place to start.'

Professor Ng said some sex problems, such as impotence in men and pain during sex in women, had biological processes at their root.

Others, such as vaginal cramps on preparing for intercourse in women and premature ejaculation in men, were more psychological. 'Once a dysfunction becomes apparent, both factors interact to cause a vicious cycle,' he said.

Asked if he personally believed in Chinese traditional medicine as a means of remedying sexual dysfunction, Professor Ng said: 'Yes, possibly, but to actually use or recommend it for treatment needs adequate scientific support, just as with all the other drugs we [registered doctors] use for various other conditions.'

Professor Ng also said that Chinese women played a more passive role than men in handling their sex problems.

'Females are generally more prone [to having sex problems] but they come less for treatment,' he said. 'The ratio between women and men receiving treatment for sex problems is approximately four to three. Women just tolerate the problems. For men, they usually seek self treatment first like herbs, food, or exercises.

'A lot of people still think it is not a serious problem worth putting money or effort into. Many doctors do not think it is an important sub-specialty either.'

GlaxoSmithKline product manager Tong Ka-kei said impotence drugs were to some degree insulated against the ups and downs of the economy because 'sex is a basic need in humans'.

'So we believe customers would not mind spending money to improve their sex life despite economic hardship,' Mr Tong said.

Bayer HealthCare Hong Kong general manager John Lo Yeung-chi said his company believed impotence drugs still had enormous market potential in Hong Kong - even though Levitra was seen as a latecomer - after both Viagra and Cialis.

His belief is based on previous market research that showed a rise in the number of Hong Kong males suffering from severe impotency was compounding at an annual growth rate of 2 per cent, mainly due to ageing.

The company estimated that more than 200,000 men aged 30 and older in Hong Kong, or more than 6 per cent of the male population from that age group had serious erectile dysfunction. The market research also indicated that only 46,000 men with erectile dysfunction, accounting for just 23 per cent of the target market, were on prescribed impotence drugs. Thirty-five per cent were on Chinese traditional medicine and 42 per cent just left the problem untreated.

GlaxoSmithKline corporate communication director Bill Fok Chi-shing sees this as an opportunity.

'There are market needs which have not been matched, such as those who try alternative medicines but find that the products fail to meet their satisfaction,' Mr Fok said.

Mr Fok said Levitra now had 15 per cent of the market share in Hong Kong, but the company was trying to win over more of the remaining patient population who had serious erectile dysfunction problems but had not used any of the three impotence drugs registered in Hong Kong.

'Our product is clinically proven. So we believe some patients who find Chinese traditional medicine is not working may come over to western medicine,' Mr Fok said.

He agreed that the affordability of drugs among potential users was one of the major considerations the company took into account when planning its business strategy. 'Hong Kong people in general can afford the drug,' he said.

As a result, Hong Kong was among the first cities to have Levitra on its shelves. The product was not available on the mainland until October last year.

'As a matter of fact, the product was sold [earlier] in Singapore because the country's registration system is simpler than the one in Hong Kong,' he said.

Meanwhile, Saw Lip-boon, chairman and chief executive officer of Zestra Asia Limited, admitted Hong Kong was only a starting point and the company would expand its sales to the mainland, a much bigger market.

At the launch ceremony of the product in Hong Kong last month, Mr Saw denied that Hong Kong women suffered more serious sex problems than women elsewhere. This had nothing to do with the company's decision of where in Asia it launched its product.

Mr Saw explained the company's decision was more based on Hong Kong being an international city.

Martin Crosby, the pharmaceutical chemist who invented Zestra, warned that female sexual dysfunction was a global problem but said Chinese women were more reluctant to share their problems with doctors due to the Chinese culture.

During the launch, Mr Crosby cited a finding from the Journal of Urology's November issue which showed 39 per cent of women aged 40 and above were affected by at least one sexual problem, with the most common problem being a declining level of interest in sex.

'Perhaps it [the problem of declining libido] is even bigger in Asia as a result of the fact that there is a lot more reluctance on the part of Asian women to discuss the issue with their healthcare workers,' he said.

Mr Crosby also cited a recent survey by the China Sexology Association about the situation on the mainland, with findings showing that only 7 per cent of women are willing to seek help from doctors for sex problems - compared with 37 per cent choosing not to seek help at all and the remaining 56 per cent seeking solutions from the internet or reading books.

Stress, obesity, sudden weight loss, menopause and disease are believed to be linked to sexual problems brought about by a change in women's hormone levels.

Mr Crosby noted that Hong Kong women's fascination with staying slim and their willingness to use supplements and chemicals to achieve that aim was a particular concern as it could undermine both their physical health and their sex life.