Pfizer's stab at giving diabetics insulin without needles is getting more praise than prescriptions so far.

Exubera, a powdered form inhaled through a special device, was introduced last year in a targeted launch to specialists, a debut analysts deemed disappointing. While doctors applaud Pfizer Inc.'s effort to find a new way to deliver insulin, some are concerned about the drug's long-term effects on the lungs, cost and insurance coverage.

Observers fear Exubera won't fare much better as Pfizer expands the sales effort to primary care doctors.

"I think Pfizer will wish they had never gotten into this. I doubt they'll regain their investment," said Dr. John Buse, president-elect of the American Diabetes Association, who participated in Exubera's trials. "There is no advantage to Exubera and there may be a safety risk. I see it as my job to talk people out of (using) it."

Pfizer won't disclose Exubera's development costs but said it is a major advancement in diabetes care because needle-phobia keeps many patients from using the insulin when they would really benefit from it. Susan Silberman, Pfizer's senior vice president of worldwide commercial development, said Exubera's performance is meeting expectations.

"I think we have to manage this product differently," she said. "Insulin is intuitive. What has changed is the approach to delivery -- so (marketing) is about the education."

Pfizer already has hired approximately 900 part-time diabetes educators to explain the product to doctors and patients, and more will be added, although the company won't say how many. A small, non-branded ad campaign for the drug that doesn't mention Exubera by name started recently, and a bigger direct-to-consumer marketing effort will debut during the second quarter.

Company executives touted Exubera as one of the new drugs that would revitalize Pfizer's stagnating sales. Others, such as smoking cessation treatment Chantix, are performing well.

But some analysts said Exubera's lackluster debut is worrisome because Pfizer needs more blockbusters. Its best-selling drug, cholesterol agent Lipitor, loses patent protection as early as 2010 and development of its successor drug was scrapped last year because of safety problems.

Exubera, which Pfizer is codeveloping with Nektar Therapeutics, was introduced last September but sales for 2006 weren't report.

Les Funtleyder, an analyst at Miller Tabek & Co., doubted it would meet his sales target of $200 million for this year. Assessing Exubera's market share and the number of patients on the drug is difficult because of the way it is sold. Patients need to buy a kit which includes the device but then also need to regularly purchase blister packs and release units, which help create the mist.

"Exubera isn't going be a big driver," he said. "Pfizer needs every dollar in sales. It (Exubera) is a negative."

Others aren't as quick to judge. Deutsche Bank analyst Barbara Ryan said that while the launch has been slow, Exubera still could reach $1 billion in sales in the next few years.

Silberman insists Exubera represents a good value because its needle-free status means more people who should be taking the medicine will start, allowing them to better manage their diabetes and saving money in the long run.

Insurers don't necessarily believe Pfizer has demonstrated Exubera's value. WellPoint Inc., the country's largest insurer, is either not covering Exubera or placing it in the most restrictive tier, with higher copays, depending on the plan.

WellPoint estimates that Exubera costs 11 percent more than one popular brand of injected insulin and 22 percent more than another.

Pfizer hasn't offered enough evidence that patients will use Exubera before they begin injecting insulin or that it would really improve quality of life, said Brian Sweet, WellPoint's chief clinical pharmacy officer.

"We want to see more documentation of the value of the product," he said.

Doctors also worry about potential long-term side effects from constantly inhaling the powder into patients' lungs. Pfizer has two years of data showing the drug is safe, but doctors want to see results from longer-term studies.

"If I can treat patients now with something I know is OK, why give them something that might (eventually) hurt their lungs?" asked Dr. Michael O'Dell, director of the Family Residency Program at the North Mississippi Medical Center in Tupelo, Miss.

He added that few insurers in his region cover Exubera and that "the delivery system is still a little clumsy."

The inhaler is the size of an eyeglass case when closed. Once expanded to expose the inhalation chamber that holds the insulin mist, it is the size of a pepper mill. Patients insert blister packs of the dry powder insulin into the device, press a button and then press a lever which creates the mist. The patient inhales the cloud, sending the insulin into the lungs where it is absorbed into the bloodstream.

Some doctors said the blister packs come in limited strengths that can make it difficult to prescribe the correct amount of insulin. Also, Exubera is fast-acting insulin that is taken at mealtime; some patients still need the long-acting insulin that is delivered through needles.

Dr. Robert Fafalak said he has prescribed Exubera for patients who were hesitant to use insulin even though the pills they were taking weren't sufficiently controlling their diabetes.

"I have patients that are doing much better now. They have their sugar under control, and I think that gain outweighs concerns about long-term effects," said Fafalak, who practices in New York.

Jamie Villastrigo, 51, a secretary who lives in Boerne, Texas, began taking Exubera three years ago as part of a clinical trial and has become a fan. She doesn't pay for the drug because she is still in a clinical trial.

"There is a concern about the cost and whether my insurance will pay for it," Villastrigo said. "But I've still got another year and a half in the program. "

Villastrigo said Exubera hasn't affected her lungs and has allowed her to cut her daily insulin shots to one from four. She maintains that the device is easy to use, and she has no qualms about using it in restaurants or public places where she'd never pull out a syringe.

"It is just easy. It gives me more freedom," she said.