For decades, it seems, humble Epsom salts (magnesium sulfate) has been saving American lives, but, until now, without reliable evidence that it really works or that it does more good than harm. Doctors in the US employ the medicine, not for laxative purposes but to combat pre-eclampsia in expectant mothers. This is a life-threatening condition characterized by a sudden increase in blood pressure in late pregnancy; it is considered one of the most dangerous and least understood complications of late pregnancy.

According to WHO, Epsom salts has seldom been used outside the US against pre-eclampsia, except where American obstetrics instructors influenced local medical practice. Yet, pre-eclampsia and full-blown eclampsia affect 10 percent of expectant mothers worldwide and are responsible for 12 percent of deaths related to pregnancy, the UN agency estimates. In developing countries, the condition is even more common than it is in the US and other industrialized nations.

Injecting magnesium sulfate can halve the risk of dangerous seizures and save lives, a comprehensive study has found. An ethics board that oversaw the trial called an early halt to the study, because the results were so impressive that they did not want to deprive women at risk who were not getting the benefits of Epsom salts therapy.

The British medical journal The Lancet reported the results last week and declared them definitive. WHO says that the question whether Epsom salts can prevent an initial seizure now is answered, affirmatively.

The three-year-long study was paid for by the United Kingdom medical research council, with support from a Geneva-based reproductive health program; WHO; the UK Department for International Development; and a European Union research program. It was conducted in 33 countries and involved 10,000 pregnant women.

Up to 60,000 deaths a year from eclampsia are reported. These needless fatalities are not only a terrible tragedy, but one that was multiplied in families where other children and household members depended on the stricken mother, notes Tomris Turmen, MD, WHO's family and community health chief.

Lelia Dulay, an obstetrics epidemiologist at Oxford University who led the research team, says, "Eclampsia is a devastating condition that can kill both mother and child. Our trial has shown that giving magnesium sulfate injections could save countless lives across the world if it could be given routinely to pregnant women with pre-eclampsia. Importantly, it is a very inexpensive treatment, making it especially suitable for use in low income countries."

But at present it is not the standard treatment in most developing countries, Paul van Look, another WHO medical expert, points out. The agency's Making Pregnancy Safer program now has a better chance of getting the drug more widely used, he says; especially in developing countries, where the incidence of matenal mortality is highest.

One reason why Epsom salts has not been given its due, says Jose Villar, a research scientist who coordinated WHO's participation in the trial, is that, hitherto, the evidence of efficacy was not sufficiently compelling. He estimates that 35,000 eclampsia cases in 143 developing countries could be prevented annually by recourse to Epsom salts therapy.

However, the treatment demands skill. According to medical literature, there is a fine line between therapy and toxicity.