Viagra might rescue risky pregnancies

From San Diego, at the Experimental Biology 2005 meeting

Roughly one in 20 women develops high blood pressure during pregnancy, a condition known as preeclampsia. Untreated, it can threaten the lives of both mother and baby. A new rodent study now shows promise for limiting preeclampsia’s threat with Viagra, or sildenafil citrate, the popular drug for erectile dysfunction.

Arteries feeding a pregnant woman’s uterus must support 10 times as much blood flow as normal. If the arteries don’t grow quickly enough to accommodate the extra blood, pressure builds up within them, says George Osol of the University of Vermont College of Medicine in Burlington.

To create an animal model of preeclampsia, Osol and his colleagues injected pregnant rats with a drug that inhibits blood vessels from releasing nitric oxide, a molecule that normally relaxes vessels so that they can expand. The pregnant rats’ blood pressure soon climbed and the growth of vessels supplying the animals’ uteruses slowed. The biggest impact was on fetuses: Eleven percent died, and surviving pups were born 20 percent smaller than normal.

Viagra aids erections in men by enhancing the effect that nitric oxide has in expanding certain blood vessels. When Osol’s team put the drug in the nitric oxide–inhibited rats’ drinking water for the rodent equivalent of the last two trimesters of pregnancy, all the pups survived and were born at normal weights.

Moreover, growth of the blood vessels supplying the animals’ uteruses, although not quite normal, was greater than in the pregnant rats with high blood pressure and not receiving Viagra.