The authorities in Brazil are considering plans to ensure that the American drug Viagra, for the treatment of male impotence, will be sold by medical prescription, because of deaths associated with taking it.

The drug will be officially on sale in Brazil from early June, but it has been available on the black market for a couple of weeks.

Strong demand for the drug has also been reported in Italy, where hundreds of people have travelled to the independent enclave of San Marino to buy Viagra.