Fibromyalgia is a real disease. Or so says Pfizer in a new television advertising campaign for Lyrica, the first medicine approved to treat the pain condition, whose very existence is questioned by some doctors.

For patient advocacy groups and doctors who specialize in fibromyalgia, the Lyrica approval is a milestone. They say they hope Lyrica and two other drugs that may be approved this year will legitimize fibromyalgia, just as Prozac brought depression into the mainstream.

But other doctors — including the one who wrote the 1990 paper that defined fibromyalgia but who has since changed his mind — say the disease does not exist and that Lyrica and the other drugs will be taken by millions of people who do not need them.

As diagnosed, fibromyalgia primarily affects middle-age women and is characterized by chronic, widespread pain of unknown origin. Many of its sufferers are afflicted by a raft of other similarly nebulous conditions, like irritable bowel syndrome.

Because fibromyalgia patients typically do not respond to conventional painkillers like aspirin, drug companies are focusing on medicines like Lyrica that affect the brain and the perception of pain.

Advocacy groups and doctors who treat fibromyalgia estimate that 2 to 4 percent of adult Americans, as many as 10 million people, suffer from the disorder.

Those figures are sharply disputed by those doctors who do not consider fibromyalgia a medically recognizable illness and who say that diagnosing the condition actually worsens suffering by causing patients to obsess over aches that other people simply tolerate. Further, they warn that Lyrica's side effects, which include severe weight gain, dizziness and edema, are very real, even if fibromyalgia is not.

Despite the controversy, the American College of Rheumatology, the Food and Drug Administration and insurers recognize fibromyalgia as a diagnosable disease. And drug companies are aggressively pursuing fibromyalgia treatments.

Hoping to follow Pfizer's lead, Eli Lilly and Forest Laboratories have asked the FDA to let them market drugs for fibromyalgia. Approval for both is likely later this year, analysts say.

Worldwide sales of Lyrica, which is also used to treat diabetic nerve pain and which received FDA approval in June for fibromyalgia, reached $1.8 billion in 2007, up 50 percent from 2006.