Health Issue: STRONG MEDICINE:

DUI...not of booze, but prescription drugs Many Painkillers, Muscle Relaxants impair Judgment Behind The Wheel     The accident that killed Kathryn Underdown had all the markings of a drunken-driving case. The car that hit her as she rode her bicycle one May evening in Miller Place, New York, did not stop, the police said,until it crashed into another vehicle farther down the road.       The driver could not keep her eyes open during an interview with investigators, according to the complaint against her, and her speech was slow and slurred. But the driver told the police that she had not been drinking; instead, the complaint said, she had taken several prescription medications, including a sedative and a muscle relaxant.         She was charged with vehicular manslaughter and driving under the influence of drugs - an increasingly common offense,law enforcement officials say, at a time when drunken-driving deaths are dropping and when prescriptions for narcotic painkillers, anti-anxiety medications, sleep aids and other powerful drugs are rampant.         The issue is vexing police officials because, unlike with alcohol, there is no agreement on what level of drugs in the blood impairs driving.         The behavioral effects of prescription medication vary widely, depending not just on the drug but on the person taking it. Some, like anti-anxiety drugs, can dull alertness and slow reaction time; others, like stimulants, can encourage risk-taking and hurt the ability to9 judge distances. Mixing prescriptions, or taking them with alcohol or illicit drugs, can exacerbate impairment and sharply increase the risk of crashing, researchers say.         "In the past it was cocaine, it was PCP, it was marijuana," said Chuck Hayes of the International Assoiation of Chiefs of Police. "Now we're into this prescription drug era that is giving us a whole new challenge."           The police also struggle with the challenge of prosecuting someone who was taking valid prescriptions. "How do we balance between people who legitimately need their prescriptions and protecting the public?" said Mark Neil, senior lawyer at the National Traffic Law Center, which works with prosecutors, "It becomes a very delicate balance."           Some American states have made it illegal to drive with any detectable level of prohibited drugs in the blood, But setting any kind of limit for prescription medications is far more complicated, partly because the complex chemistry of drugs makes their effects more difficult to predict than alcohol's And determining whether a driver took drugs soon before getting on the road can be tricky, since some linger in the body for days or weeks.