Germany's health ministry said on Friday that 616 people worldwide had died after using Viagra, but cautioned against attributing blame for the deaths to the drug.

Pfizer - the company which makes Viagra - said the drug is safe when used as prescribed.

(A) new development is young people taking Viagra with vodka for a special, but highly dangerous, push.

Ulla Schmidt Health Minister

German Health Minister Ulla Schmidt on Saturday told Germany's Neue Osnabruecker Zeitung that many of the deaths resulted from incorrect use and that Germany wanted a European inquiry into the risks posed by the drug.

"Patients with high blood pressure or heart or circulatory problems should not take this medication because it can have life-threatening side effects," she said.

"Another new development is young people taking Viagra with vodka for a special, but highly dangerous, push," she added.

Germany cannot act on its own because the drug had been authorised by the EU, the health minister told the newspaper.

Viagra responds

A spokesman for New York-based Pfizer, the world's largest pharmaceutical company, said the drug was safe when used as prescribed.

"Many patients taking Viagra have underlying cardiovascular disease, such as hypertension. Erectile dysfunction is a symptom of those conditions, so they already have risk factors for heart attack," Jeoff Cook, spokesman for Pfizer, said on Friday.

There have been reports of heart attacks among men using Viagra, but a study of 5,600 users in England this year found the drug did not increase the risk of heart attacks and heart disease.

"Well-controlled clinical trials show no difference in the incidence of heart attack or death between patients treated with Viagra and those treated with placebo," Mr Cook said.

German concerns

"Based on what we know at the moment, in many cases the incorrect use of Viagra is to blame ... I will ensure that the prescription criteria are examined," Ms Schmidt was quoted as saying.

The German Institute for Medicinal Products has received 104 reports of "suspected undesirable side-effects" among people who took the drug and has recorded 77 deaths in the EU and 30 in Germany, the health ministry said on Friday.

"In 30 of these reports it is documented that the patient died at some point in time afterwards, often as a result of cardiac or circulatory problems," the ministry said referring to the period after the drug was authorised in the EU in September 1998.

The ministry said the Swedish-based Uppsala Monitoring Centre (UMC) had recorded 616 cases of people who had died after using Viagra.

Since January 2000, the German medical authorities have recommended people with cardiac or circulatory problems should not take Viagra.

Viagra was launched in the US in 1998 and earned Pfizer more than $1bn in sales last year.

Mr Cook said 15 million men had taken Viagra since its introduction.