Within one hour on a recent afternoon in four different homes across Washington, 2-year-old twins got into the chewable vitamins, a 1-year-old took his mother's birth control pill, a 3-year-old sprayed perfume in his eye and a child ate the mercury from a broken thermometer.

Their frantic parents called the Georgetown University's National Capital Poison Control Center. Each got calm, correct information on how to deal with their individual emergencies.

Next week, Georgetown, along with 45 other certified regional poison control centers, will observe the 25th anniversary of National Poison Control Week.

"Poisons act fast; so do children," is the motto of the National Poison Prevention Week Council, which is hoping to underscore the continuing problem of accidental poisonings among the young.

Since poison prevention first came to national attention in the late 1920s with the passage of the so-called 'lye bill' -- which required warning labels on a dozen household products containing acids and alkalies -- yearly poisoning deaths among preschoolers have plummeted from about 450 in 1961 to 55 in 1983, according to the National Center for Health Statistics.

Much credit for this dramatic decline in deaths and the increased awareness that accompanied it goes to retired pediatrician Dr. Edward Press, who began the nation's first poison control center in the Chicago area in 1953.

But Press and Ken Giles, of the Consumer Product Safety Commission and secretary to the Poison Prevention Week Council, warn that accidental poisonings still occur.

"I don't think we've solved the problem of child poisonings, although the deaths are way down," Giles said. Of about 750,000 reported ingestions or near misses last year, nearly half a million involved children. "And that's a real concern.

"We may never be able to bring that exposure figure down because most adults don't pay attention to poison prevention until they find themselves parents . . . It's a continual process of education."

"Most poison control centers saw a 10 percent increase in the number of persons using their centers between 1984 and 1985," said emergency physician and toxicologist Dr. Toby Litovitz of the Georgetown center, which fielded about 34,000 calls last year. "That alone should tell you poisonings are not going away as a problem."

Press began his crusade to prevent poisonings after becoming outraged at the number of children he treated whose stomachs and esophagi had been permanently torn or scarred shut after eating corrosive lye that was commonly kept in many homes to make soap. In 1953, he brought together officials at five major medical schools in the Chicago area and persuaded them to pioneer the nation's first community poison center that same year.

"Before this, it was just emergency rooms responding as best they could on a crisis-by-crisis basis," Press, 72, said by telephone from his Portland, Ore., home.

Press and his colleagues scoured existing medical and toxicological literature for antidotes and compiled lists of the most common poisons. Their research was eventually published as a book by the American Academy of Pediatrics, which also awarded Press the Academy's first gold medal for his efforts.

A milestone in the fight against accidental poisonings came in 1972 with legislation requiring child-resistant caps on aspirin bottles and later also limited the number or pills inside bottles of children's medicine.

What Press and his colleagues started as stacks of index cards with antidote information has evolved into a sophisticated network of regional poison centers, fed by computerized data banks that are updated quarterly with the newest information on potentially lethal cosmetics, drugs, plants, insecticides, industrial and household cleansers and the latest, most efficient remedies.

"Many of the 400-plus poison control centers of the 1960s were essentially a telephone hooked up to a pharmacist's office," Giles said. "It's taken poison control centers 25 years to reach this level of action and effectiveness."

Locally, the Georgetown Hospital houses the only certified poison control center for the Washington area. Registered nurses trained in toxicology answer phones 24 hours a day, using their computers to instantly call up facts about a myriad of ingested products.

On a typical day, between 100 and 120 people will call. Most, but not all, are caretakers of small children.

"We get calls from hazardous spill sites, daycare centers, adults who ate their dog's medicine by mistake at night and parents or friends of teenagers who've attempted suicide," said registered nurse Jane Elshami, at Georgetown's poison center.

Most poisonings involving children happen between 5 p.m. and 8 p.m. when young children are hungry and parents are often most distracted, said Rose Ann Soloway, education and communications director of the Georgetown center.

"Children are at risk as soon as they can move," she said. "They'll eat tiny disc batteries dropped on the floor or pull plant leaves off table tops . . . Their tastebuds are not fully developed. Parents should not asssume that because a substance is bitter, the young child won't try it."

Soloway and others caution that -- even with child-resistant caps -- there is no substitute for "out of sight-out of reach."

Children will imitate adults and Soloway said many emergency calls come the morning after an adult party when children have drained unemptied glasses of liquor.

Two of the most lethal preparations common to most homes are anti-freeze and windshield washing fluid -- a single teaspoon can kill an adult and the symptoms are often delayed.

Other dangerous and caustic chemicals that should be kept under lock include: drain and toilet bowl cleaners, oven cleaners and rust removers, furniture polish, petroleum products, distilled alcohol and alcohol by-products found in perfumes, after shaves, mouthwash and charcoal-lighting fluids.