More than 30 companies have filed applications to register the Wei-ge brand name and, the government says, none has been approved. But this has not stopped several of them launching their pills, because they see a golden opportunity lasting until the US product enters the mainland market.

On April 15, the government announced a ban on the best-known home-made product, a pill named Wei-ge Kaitai made by a firm in the northeastern city of Shenyang, which has racked up sales of 60 million yuan (about HK$55.86 million) in 27 cities and provinces since launch in February.

The State Pharmaceutical Supervision Management Bureau said that, in applying for permission to sell the drug, the producer had not fully described the raw materials and had applied for the brand name Wei-ge, but had not been cleared to use it.

The real Viagra is undergoing clinical trials on 600 men at seven hospitals in Beijing, Shanghai and Wuhan and is not supposed to be available.

So, if you cannot arrange a passport for a trip to Hong Kong, where can you buy it? Try the four-storey Medicine Building in Wangfujing, Beijing's main shopping street. Go to the family planning counter, which is full of condoms, contraceptive pills and potency oils. Do they have Wei-ge? 'Sorry, you came too late,' said the sales lady in a white uniform and a wink in her eye.

'We have just been banned from selling the Chinese one and the American one has not arrived yet. The government is still testing it. We do not know when it will be available.

'But we have plenty of other products that have the same effect,' she said.

'How about this one, Hua Fo [China Buddha], 10 in a packet for 109.8 yuan? It sells well. It is made of natural ingredients so there are no side-effects. Viagra is made of chemicals, so you never know.' Walk down the street to another state-run pharmacy and ask in there.

'Come back in September,' said the salesman at the counter for imported drugs.

'The authorities are testing Viagra on patients and may have it approved by September. Some people say the government might postpone approval, to protect the market for Chinese medicines, but I doubt it. It should cost about 100 yuan a pill.' If the state shops cannot sell it, how about the black market? South of the Great Wall Sheraton Hotel is a row of restaurants, barbers and sex shops mainly used by migrant workers living nearby.

'Yes, we have Viagra, at 300 yuan for a pill,' said a salesman in one of the sex shops, pointing to a room at the back.

'Of course it is the real thing, smuggled in from Hong Kong. That is what our customers want.' The shop next door had neither Viagra nor home-grown pills, but stocked a potency spray also called Wei-ge. Last week, police closed down two of the barber shops which front for brothels in the street, but so far have left the sex shops undisturbed.

Before it receives government approval to sell its product, Pfizer is saying little about Wei-ge mania.

Pfizer has not said when it expects to get approval to launch its product, nor whether it will manufacture Viagra at a factory it operates in the northeastern port city of Dalian nor if it will market it as Wei-ge or under another brand name.

According to some mainland newspapers, Pfizer did not register the Wei-ge name with the authorities, which led mainland companies to apply and so sparked Wei-ge mania.

If Pfizer had already gained approval for the trademark, then other companies would not have been able to apply for it.