NEW YORK (CNNMoney.com) -- The market for painkillers for the shooting pain associated with cancer, diabetes and shingles is expected to soar over the next decade, driven by a largely untapped patient pool of millions of Americans.

The $1.7 billion market for neuropathic pain is expected to triple to $5.5 billion by 2015, according to estimates from Datamonitor, a stock research firm.

The market is being driven by fast-growing demand for Pfizer's (Charts) Lyrica and Eli Lilly & Co.'s (Charts) Cymbalta, both pills, and Endo Pharmaceuticals' (Charts) Lidoderm patch.

Sales of neuropathic painkillers, while dwarfed by the markets for drugs for heart disease, cancer and other medicines, are important as big drugmakers seek to squeeze every last dollar of earnings from the billions they spend developing new drugs.

Many neuropathic patients don't realize the source of their pain is damaged nerves and they're not receiving proper treatment, industry analysts say, fueling the potential for rapid growth in that business.

"The patients are there, and [neuropathic pain] is under-treated and under-diagnosed," said Ben Greener, senior analyst for Datamonitor. Greener said that Pfizer gave a boost to its launch of Lyrica late last year by educating physicians on neuropathic pain.

"Lyrica is very impressive, and I've no doubt that Lyrica will go on growing," said Greener, who estimates that annual Lyrica sales from neuropathic pain will exceed $2 billion in 2015, not including revenue from treatment of other types of pain.

Lyrica sales totaled $463 million in the first half of 2006, and Pfizer has set a $1 billion goal for the year for all indications, calling it one of its most successful drug launches ever.

Lilly's Cymbalta, used mainly as an antidepressant, has been approved by the Food and Drug Administration to treat nerve pain associated with diabetes, and the company is conducting late-stage studies to treat other forms of chronic pain.

Cymbalta sales totaled $544 million for the first six months of 2006, and $680 million for all of 2005, though it isn't easy to quantify how much of those sales are from pain treatment and how much are from treating depression.

Greener of Datamonitor estimated that annual Cymbalta sales from nerve pain will reach nearly $1 billion by 2015, not including sales for depression and other indications.

Endo Pharmaceuticals' Lidoderm, a patch for treatment of pain related to the blister-rash known as shingles, totaled $419 million in 2005 sales, accounting for more than half the company's revenue that year, and totaled $266 million for the first half of 2006.

But the threat of a patent challenge to Endo's drug is giving the company some trouble. Citigroup downgraded Endo to "sell" on Wednesday, triggering a 13 percent plunge in the company's stock, because Citigroup analysts believe Endo could get squeezed by generic competition by 2010.

Some 50 million Americans are in need of pain treatment, including but not specific to neuropathic pain, according to the National Foundation for the Treatment of Pain. The Houston-based organization said that pain sufferers have nearly 20 times the suicide rate of the general population, and that 75 percent of cancer patients are not receiving suitable treatment for their pain.

Corey Davis, analyst for Natexis Bleichroeder, described the neuropathic pain market as "enormous and under-served," with plenty of room for more growth.

Cephalon (up $0.38 to $70.09, Charts), a biotech based in Frazer, Pa., could be the next company to launch a drug for neuropathic pain. Cephalon just got its drug Fentora approved by the FDA last month for shooting pain in cancer patients. The company is also testing Fentora for treatment of back pain and other forms of neuropathic pain. Cephalon hopes to file an application to the FDA for neuropathic pain treatment in 2007.

Allergan (Charts), the California-based maker of Botox, has an even more promising pipeline, and could be the next company to unveil a blockbuster neuropathic painkiller, said Davis of Natexis Bleichroeder.

"The sexiest thing that I've seen in development for neuropathic pain is from Allergan," said Davis.

Allergan confirmed that it's studying two potential neuropathic painkillers but declined to specify what they're called.

Davis, the analyst, said that so far the experimental drugs have shown "very strong efficacy and virtually no side effects."

If either one of the Allergan drugs succeeds in clinical trials and is approved by the FDA, it "would indeed be the blockbuster that could dominate the market," said Davis.

The analysts interviewed for this story do not own shares of the company stocks mentioned here.

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