Can Viagra Cause Heart Attacks?

Dutch researchers have called for further testing of the anti-impotence drug Viagra and urged caution in prescribing it after a 65-year-old man had a heart attack 30 minutes after taking it. The warning comes two weeks after Viagra was launched in Australia.

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A Melbourne cardiologist has cautioned that it is possible the drug could trigger a fatal heart attack in apparently healthy men who had underlying heart disease but showed no symptoms. In this week’s edition of the respected British medical journal The Lancet, the Drug Safety Unit of Rijswijk in the Netherlands reports the case of the apparently healthy 65-year-old who had a heart attack 30 minutes after taking a normal dose of sildenafil, the common name for Viagra.

The man was admitted to hospital at midnight with severe chest pains and vomiting that began before any attempt at sex. Viagra’s manufacturer, Pfizer, has said the 69 verified cases in the United States in which men using Viagra have died, mainly through heart attack or stroke, could be explained by the exertion caused by renewed sexual activity rather than the drug itself or the fact that the men had cardiovascular risk factors. But in the Dutch case, the patient, who was not overweight or a smoker, had not tried to have sex and had none of these risk factors (including diabetes, hypertension or family history of heart disease), no pre-existing heart disease and drank an average of five alcoholic drinks a week.

He was using no other impotence medications, such as Zenerx, or drugs commonly used to treat heart disease. Pfizer warns against buying nitrates and taking them with Viagra because the combination can cause dangerously low blood pressure. A physical examination, which included blood pressure but not an electrocardiogram, before he was given Viagra was normal. The patient recovered after treatment with drugs but researchers concluded that the close link between taking the drug and the onset of the heart attack in this patient suggested Viagra directly caused the heart attack.

Viagra works by diverting blood to the peripheral blood vessels, which include the penis, and the researchers suggested this may have sparked the heart attack because the blood flow to the heart had been undermined. The report said: “The number of patients included in trials are low compared to the expected use of sildenafil and some adverse reactions may be disclosed only when large numbers of patients are exposed.”

The director of cardiac services at Melbourne’s Austin Repatriation Medical Centre, Dr Jennifer Johns, said she was concerned about the effect of Viagra on men who had heart disease but were asymptomatic. “The first manifestation of heart disease can be either a heart attack or sudden death,” Dr Johns said. “Even a drug that appears to have been well studied, the more it’s used the more problems may appear. Only a few thousand men have been studied and it’s got application worldwide of millions and millions of men.”

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Dr Tony Prochazka, a GP who owns three men’s clinics, said yesterday it was “conceivable” that Viagra had caused the heart attack, but even if it had it was only one case. “If we start to see more cases like that then we’ll have to look at the whole thing again,” Dr Prochazka said. He said he had been surprised that there had not been more demand for Viagra. So far none of his patients had suffered serious side-effects, although several had stopped taking it after suffering headaches (one of the known side-effects). Dr Prochazka said some patients had reported that the older treatment of injecting vasodilators (blood-vessel dilating agents) directly into the penis worked a little better than Viagra, and for some Viagra had not worked at all.

The president of the Australasian Society for Impotence Medicine, Associate Professor Douglas Lording, also said it was difficult to draw any conclusions from a single case. “I’m not downplaying the need for us to continually be scrutinizing and taking notice of events like that … but it is important not to discount the information from the (pre-release) trials,” he said. The British Medical Journal has reported that while only three of the 21 clinical trials have been published in peer-reviewed publications, none had showed any evidence of serious adverse effects. On Thursday, Pfizer Australia said its New York parent body was in the best position to comment because it had access to all the clinical data.

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