NEW YORK (CNN/Money) - A new diabetes treatment from Eli Lilly and Amylin that is extracted from the saliva of the Gila monster received approval from the Food and Drug Administration Friday, but analysts believe sales might be lackluster because patients are afraid of needles.

"The issue here is how many people are willing to take a twice a day injection," said Scott Henry, analyst for Oppenheimer & Co. "If someone says you can take a pill or shoot yourself with a needle twice a day, the pill is starting to look pretty good."

Byetta, which was co-developed by both companies, improves blood sugar control in patients with type 2 diabetes, according to Amylin Pharmaceuticals (up $0.20 to $34.78, Research) and Eli Lilly and Co (up $0.17 to $50.07, Research). The drug, developed from a compound in the toxic saliva of a rare lizard found only in the Southwest U.S. and Mexico, will be available June 1 for patients who aren't getting enough insulin, the companies said.

Amylin stock prices dropped on the news, while Eli Lilly stock edged higher.

The market potential, though, is huge. There are 18.2 million diabetics in the U.S., according to the American Diabetes Association. But analysts are concerned that many patients with type 2 diabetes, which is less serious than type 1, won't happily switch to injectable treatments.

"The issue in getting patients from oral medicine to injectable is that there is less of a desire to use the product," said David Moskowitz, analyst for Friedman, Billings, Ramsey & Co. "The uptick could be slow initially."

Henry projected Byetta sales would reach $60 million 2005 and $190 million in 2006.

New product sales will likely have more of an impact on Amylin, a San Diego-based company that reported $34.3 million in sales and a net loss of $157.2 million in 2004, than its larger partner. Eli Lilly, based in Indianapolis, had $13.9 billion in worldwide sales last year, and its top selling blockbuster was Zyprexa, a treatment for schizophrenia and bipolar mania that made $4.4 billion.

The approval of Byetta is the second FDA approval for an Amylin product since last month. On March 16, the FDA approved Symlin, an injectable drug to be used with in conjunction with insulin for patients of types 1 and 2 diabetes. The drug will be available by mid-June, the company said.