Viagra not only fights impotence but also reduces heart stress

VIAGRA not only fights impotence but also reduces the harmful effect of stress on the heart, scientists claimed yesterday.

Scientists tested the anti- impotence drug, sildenafil citrate, on 35 men and women who were given injections of an adrenaline-like chemical.

The chemical, dobutamine, mimics the effects of emotional or physical stress by increasing the force of heartbeats and boosting the flow of blood through the body.

The researchers found that Viagra slowed the increase in the strength of heart contractions by half, from 150% to about 75%.

Professor David Kass, from Johns Hopkins University School of Medicine in Baltimore, Maryland, USA, who led the study, said: “Sildenafil effectively puts a ‘brake’ on chemical stimulation of the heart.”

Earlier research showed that Viagra can reverse the effects of weakened and enlarged heart muscle in mice.

The new study provides the first evidence that Viagra can have a beneficial impact on the hearts of humans.

Volunteers taking part in the research were all healthy, with an average age of 30 and no previous signs of artery disease.

All participants were first given dobutamine injections and then randomly assigned to two groups, either treated with Viagra or a sugar pill placebo.

They were then given a second injection to see if taking Viagra made any difference to the effect of the dobutamine.

After the first injection, the force of heart contractions rose by 150% in all the volunteers.

The increase was repeated in the placebo group after the second injection. But in the group treated with Viagra, it was reduced by 50%.

Heart function in the Viagra group was not altered in any way between injections, showing that the effect is only seen under stressful conditions.

Prof Kass said: “Until now, it was widely thought that drugs like sildenafil had no effects on the human heart and that its only purpose was vasodilation in the penis and the lungs.

“Our results set the stage for further studies of sildenafil’s immediate and long-term effects on the heart and its ability to modify other neuro-hormonal and stress stimuli, including adrenaline and hypertension (high blood pressure).”

Viagra is known to work by stopping the action of an enzyme called phosphodiesterase 5 (PDE5A).

The enzyme is involved in the breakdown of a key molecule called cyclic GMP which helps control stress and limit overgrowth in the heart. Blocking PDE5A in the penis also helps to maintain erections.