Reports from Brazil say supplies of Viagra, the drug used to treat male impotence, were sold out within hours of going on sale.

Many pharmacies have had to call for new shipments of the American-made drug.

One chemist in Rio de Janeiro said he found two men waiting outside his shop when he opened for business at seven o'clock in the morning.

Viagra is only available in Brazil with a doctor's prescription and costs around fifty dollars.But a black market is flourishing.

At least two men are said to have died after taking the drug without medical supervision, prompting the Brazilian authorities to bring forward Viagra's official launch.