NEW YORK — 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 they would benefit from. 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-timers 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, will lose patent protection as early as 2010 and development of its successor drug was scrapped last year because of safety problems. Exubera was introduced in September but 2006 sales weren't reported.

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 device kit, 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's needle-free method 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 that. WellPoint Inc., the country's largest insurer, is either not covering Exubera or placing it in the most restrictive tier, with higher co-pays, 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. "We want to see more documentation of the value of the product," said Brian Sweet, WellPoint's chief clinical pharmacy officer.

Some doctors worry about potential long-term side effects to patients from constantly inhaling the powder into their lungs. Pfizer has two years of data concluding that the drug is safe, but some doctors want to see results from longer-term studies.

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 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 taken at mealtime; some patients still need the long-acting insulin delivered through needles.