After 12 years of debate, officials of the Food and Drug Administration say they will soon recommend continued use of a controversial stimulant contained in nonprescription cold medications and diet pills.

Some obesity experts and consumer advocates have argued that phenylpropanolamine hydrochloride (PPA) -- a chemical cousin of drugs such as adrenalin and amphetamines -- should be banned in over-the-counter drugs because it can raise blood pressure and has the potential for misuse. Experts are particularly concerned about children and adolescents who take large quantities of diet pills to lose weight and may consume more than the recommended dose of PPA.

The ingredient is found in more than 75 nonprescription medicines, including the diet pills Acutrim, Appedrine, Control and Dexatrim as well as cold and cough remedies such as Bayer Children's Cough Syrup, Comtrex Multi-Symptom Cold Reliever and Triaminic.

PPA, a decongestant, opens clogged nasal passages. It also suppresses appetite, a fact that makes it appealing to dieters.

Last week, just days after the FDA removed 111 other nonprescription drugs from the market, the agency's division of over-the-counter drugs decided at an internal meeting to keep PPA in cold remedies.

PPA "is safe and there are no questions about its efficacy as a decongestant when taken as directed," said William Gilbertson, director of the FDA's over-the-counter drug division, which reviewed the ingredient's safety.

A similar review of PPA's value as an appetite suppressant is nearing completion, Gilbertson said. While that question "is somewhat different and more complicated, it looks like we will still recommend that PPA is safe for use with enhanced {warning} labeling," he said.

At the same time, the FDA will recommend a slight reduction in the four-hour dosage of PPA in decongestants -- a minor change first proposed by one drug manufacturer. The change is so small, drug companies said, that consumers would probably never notice it.

Manufacturers said last week that they felt vindicated by the FDA decision. "We feel that it is long overdue," said Leonard Fantasia, vice president of scientific affairs for Ciba Consumer Pharmaceuticals, makers of Acutrim.

But a variety of consumer and health groups concerned about the side effects of PPA say they are not satisfied and have called for stricter regulation of the drug. An estimated five billion doses are sold annually in the U.S. and products containing PPA account for an estimated $200 million in sales, according to the American Society of Bariatric Physicians.

Officials of Public Citizen, the nonprofit health group founded by consumer advocate Ralph Nader, say that PPA, even in small amounts in over-the-counter drugs, poses a health risk to consumers. "We think that PPA should be taken off the market," said Sidney M. Wolfe, Public Citizen's director.

Studies have shown that most people do not suffer side effects after taking low doses. But two reports cited in recent congressional hearings found that a small number -- from 2 to 9 percent of users -- experienced a rise in blood pressure to potentially dangerous levels and suffered chest pain or angina.

Wolfe raises questions about the effectiveness of PPA, as well. A stuffy nose, he said, is best treated for a short period of time with a nasal spray, not with pills.

The usefulness of PPA in achieving weight loss is also controversial. The American Society of Bariatric Physicians recommends the drug only if it is part of a physician-supervised weight-loss program that includes exercise and other lifestyle changes.

Studies show that it leads to about half a pound to a pound of weight loss each week. "It's helpful in losing a little bit of weight," said Albert Stunkard, an obesity expert at the University of Pennsylvania, "but you regain it when you stop using the drug."

Those who take diet pills to shed extra pounds are also likely to be at risk for high blood pressure, diabetes and other health problems of which they are unaware and which can be exacerbated by PPA. "Look at the chemical structure of PPA, it's almost identical to amphetamines, epinephrine and adrenalin," Wolfe said. "It's magical thinking that this drug will only do good things for you and not present a risk of high blood pressure, strokes and worsening of diabetes. That's just silly delusional thinking, consistent with Madison Avenue, however."

But other studies have demonstrated PPA's relative lack of side effects and its effectiveness as a cold remedy and weight-loss aid.

Introduced in 1939 as an asthma drug, PPA quickly was recognized as a nasal decongestant and has been an ingredient in cold medications for almost 50 years. In 1978, it was approved by an FDA advisory committee for use as an appetite suppressant.

"We are attuned and sensitive to the concerns that have been raised, but there are people on both sides of these issues and it's important to weigh the concerns with the consumer benefits," the FDA's Gilbertson said. "We want to provide safe and effective products."

PPA "can be used safely by large numbers of persons," said Paul Raford, a family practice physician with the U.S. Public Health Service. "That is what laboratory safety studies generally show."

Yet there is growing alarm among health officials and physicians about the use of diet pills by teenage girls who are often already obsessed with staying thin and looking for a quick fix. Drug manufacturers stress that the products are aimed at adults. But at hearings held in September by the House Subcommittee on Regulation, Business Opportunities and Energy, obesity experts said they were concerned about the abuse of PPA by children and adolescents who are misusing the medications for weight control.

A 1986 report by the Centers for Disease Control found that nearly 7 percent of eighth-grade and 10th-grade girls have used either diet pills or diet candies to control their weight. Warning labels on over-the-counter diet products caution users to consult their physicians if they are under 18.

But surveys of 2,430 undergraduates at Michigan State University found that "none of the women who had used diet pills had ever consulted their physicians about their use," said Lawrence R. Krupka, who conducted the surveys.

Many consumers don't understand the potential hazard of taking several over-the-counter drugs at once. The survey found that of those who took diet pills, almost 25 percent were also using other medications containing PPA at the same time -- a practice that places them at increased risk for complications. In congressional testimony, Krupka told of one dieter suffering from a severe cold who had taken one diet pill and four decongestant tablets within 24 hours. She did not have any adverse reaction, but the amount of PPA she took -- 675 mg. -- is roughly four times the recommended dose.

"The difference between the therapeutic and the toxic dose can be extremely small and is quite different for different people," said Thaddeus Prout, chairman of the department of medicine at the Greater Baltimore Medical Center, and a longtime critic of PPA.

The debate over PPA-containing drugs began in 1978, when an advisory panel of the FDA first found the drugs to be safe and effective. Despite the FDA's decision to permit continued use of PPA in cold medicines and diet pills, the controversy is not likely to abate.