The anti-impotence drug viagra offers a potential treatment for pregnant women at risk of developing preeclampsia

The anti-impotence drug viagra offers a potential treatment for pregnant women at risk of developing preeclampsia, US researchers report.

Preeclampsia affects about 10 per cent of pregnancies. Arteries that supply the uterus with blood during normal pregnancy enlarge and increase uterine blood flow more than tenfold. This adaptation, characteristic of mammals, fails during preeclampsia, reducing the supply of nutrients to the foetus and blood supply to the uterus during labour.

Viagra (sildenafil citrate) was originally investigated as a treatment for angina. It ended up as the world market leader oral treatment for erectile dysfunction when unexpected side effects showed up in trials. The drug is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Inhibiting this enzyme triggers the release of nitric oxide, which in turn increases blood flow.

Researchers at the University of Vermont College of Medicine, Burlington, treated pregnant, hypertensive rats with viagra and found that arteries of the uterus grew as they should during pregnancy.

Arterial diameters of viagra-treated animals didn’t quite match control values, ’but were significantly larger than those with hypertension, suggesting that viagra may have increased blood flow to the uterus and placenta,’ said research director George Osol, professor of obstetrics and gynaecology.

In addition, fetal weights - reduced by over 20 per cent in untreated animals - were normal following treatment. Further evidence for an increase in uterine blood flow, says Osol.

The researchers were surprised to find that viagra completely prevented foetal mortality. Six out of 52 foetuses were lost in the hypertensive group, says Osol, but none were lost in the viagra-treated group, even though they remained hypertensive.

The benefits of Viagra were not associated with reduced maternal blood pressure, he adds, so hypertension per se is not linked with the loss of NO signalling in the uterine circulation. ’This is an important distinction, because it demonstrates a selective effect of Viagra on the uteroplacental circulation and avoids some of the complications of antihypertensive therapy during pregnancy, particularly the danger of reducing uteroplacental blood flow (placental underperfusion) secondary to the reduction of systemic blood pressure,’ said Osol.

Bea Perks