Some psychoactive drugs ease harsh PMS.

Drugs such as widely prescribed Prozac can relieve a severe form of premenstrual syndrome (PMS), according to a new analysis of 15 past studies.

Physicians prescribe these drugs, called selective serotonin reuptake inhibitors (SSRIs), with considerable success against depression, but their effectiveness against severe PMS has been less clear. While many women in PMS research trials report relief with SSRIs, so do some receiving inert placebos.

The new review by scientists in England evaluates the experiences of 570 women who had been randomly assigned to receive SSRIs in various studies and 435 others who took placebos. Neither patients nor the researchers who evaluated them knew which women received the actual medication.

The women kept diaries of their symptoms. The findings revealed that women getting SSRIs were nearly seven times as likely as the others to report relief from the irritability, depression, and anxiety of severe PMS, the researchers say in the Sept. 30 LANCET. Women getting the drug also reported, on average, less bloating and fewer cramps.

About 5 percent of women who menstruate encounter severe PMS symptoms just before their monthly period, says study coauthor Paul W. Dimmock of Keele University and North Staffordshire Hospital in Stoke-on-Trent, England. Such symptoms can disrupt family life and cause women to miss work, he says.

The analysis found that daily doses taken only during the 2 weeks leading up to the menstrual period often worked as well as month-long treatment. The shorter regimen would cost less and may provoke fewer side effects. SSRIs themselves can cause insomnia, fatigue, and gastrointestinal problems.

Scientists are now determining how few days each month women need to take SSRIs to allay severe PMS, says Peter J. Schmidt of the National Institute of Mental Health in Bethesda, Md.

The Food and Drug Administration has approved a prescription formulation of Prozac called Sarafem for severe PMS. Nevertheless, say both Dimmock and Schmidt, SSRIs remain underprescribed for this condition.