Much of that growth will be fueled by an aging global population—suffering from arthritis, cancer, diabetic neuropathy, and postoperative pain. But those patients—and, in fact, most patients—will receive more palliative care than in the past because of society's changing attitude toward pain management.

"In the old school of thinking, patients were hesitant to ask for more analgesics," says Carol Ammon, CEO of Endo Pharmaceuticals, a specialty pharma with a focus on pain products. "Patients were socialized to accept a certain amount of pain. I think a lot of that has gone out the window now. Patients realize that they can appropriately have their pain treated and that they are not bad patients for asking to have it treated."

Global Market Growth, Global Market Share

Defined and Indicated The International Association for the Study of Pain (IASP) defines pain as "an unpleasant sensory and emotional experience in association with actual or potential tissue damage, or described in terms of such damage." For patients, it's just a big hurt, but for doctors and pharma companies seeking FDA indications, pain is typically categorized by duration: acute (postoperative pain) or chronic (low-back pain). Chronic pain is defined as pain that lasts more than six months, and acute pain is a condition experienced for less than six months.

Another category, neuropathic pain, is usually chronic and is caused by lesions in the peripheral or central nervous system. Various medical conditions and external factors, including diabetes, herpes zoster (shingles), cancer, exposure to toxic substances (including chemotherapy), alcoholism, stroke, HIV, and multiple sclerosis can all lead to neuropathic pain.

Breakthrough pain refers to intermittent flares experienced by patients who are already on a fixed, around-the-clock pain therapy regimen. An episode can last anywhere from just a few seconds to several hours and can be triggered by a specific activity (coughing or moving) or may start unexpectedly and for no reason.

Available therapeutics for pain can be classified in three categories: nonopioids, opioids, and adjuvants. The nonopioids include nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen (Tylenol). NSAIDs constitute the majority of this category; they range from traditional, over-the-counter pain relievers (including aspirin, ibuprofen, and naproxen) to newer, prescription COX-2 inhibitors (including celecoxib, rofecoxib, and valdecoxib).

NSAIDs act by inhibiting the conversion of arachindonic acid to prostaglandin, a substance produced by the body that plays a role in inflammation and pain. Although traditional NSAIDs are considered relatively safe, COX-2 inhibitors have fallen under increased scrutiny following Merck's voluntary withdrawal of Vioxx (rofecoxib), because of research showing increased risks of heart attacks and strokes.