Neuropathic Pain

Neuropathic pain is caused by damage to the nerve tissue and affects 15.2 million people in the United States, whether it be due to alcoholism. amputation, sciatica problems, cancer chemotherapy, diabetes, facial nerve problems, HIV infection, multiple sclerosis, phantom limb syndrome, shingles, or spine surgery. The four major conditions that cause neuropathic pain are diabetic neuropathy, postherpetic neuralgia, trigeminal neuralgia, and HIV/AIDS neuropathy. The total number of neuropathic pain sufferers that need treatment in the United States is expected to rise from 15.2 million in 2003 to 19.5 million in 2010 at a compound annual growth rate of 3.6 percent. This growth is expected to be driven mainly by the increasing number of people suffering from neuropathic pain as a diabetic complication. Figure 2-1 and Chart 2.4 depict the prevalence of neuropathic pain in the United States from 2000 to 2010.

The most common cause of neuropathic pain is diabetes. According to the American Diabetes Association (ADA), there are 18.2 million people suffering have diabetes. The ADA estimates that between 60 and 70 percent of diabetics have mild to severe forms of neuropathy. In 2003, it is estimated that 11.4 million diabetics suffered from some form of neuropathy (although only a minority of these experience symptoms that require chronic pharmacological treatment), and this number is expected to rise to 15.0 million by 2010 as the incidence of diabetes escalates due to the obesity epidemic in the United States The number of diabetic neuropathic pain sufferers in need of year-round pharmacological treatment is currently estimated to be 3.8 million, and growing at an annual incidence rate of approximately 2 percent. Diabetic neuropathy represents the biggest opportunity for market participants because of the large patient population and the fact that currently, no products on the market have an indication for it. Chart 2.5 presents the prevalence of diabetes and diabetic neuropathy in the U.S from 2000 to 2010.

Postherpetic neuralgia (PHN) is an offshoot of shingles. Not everyone who has had chicken pox will get shingles, and not everyone who gets shingles will develop PHN. The older the person, the greater his or her risk of developing postherpetic neuralgia. Approximately 25 percent of people over 55, 50 percent of people over 60, and 75 percent of people over 70 are estimated to eventually develop postherpetic neuralgia after contracting shingles. Overall, approximately 20 percent of those with shingles will eventually develop postherpetic neuralgia. As the demographics of the U.S. population continue to shift toward the elderly, an increasing number of shingles outbreaks is likely. The Administration on Aging (AoA) estimates that the number of Americans aged 65 or older will grow from 35.9 million in 2003 to 71.5 million in 2030 at a compound annual growth rate of 2.5 percent. Currently, there are 961,000 Americans in 2003 suffering from shingles. The number of PHN sufferers in need of treatment is currently estimated to be at 206,000 and projected to rise to 252,000 by 2010 at a compound annual growth rate of 2.9 percent. Chart 2.6 presents the prevalence of shingles and postherpetic neuralgia in the U.S. from 2000 to 2010.

Neuropathic pain is a common complication of antiretroviral treatment for HIV and is estimated to affect about 15 percent of the prevalent patient population. As advances in antiretroviral treatment are made and patients live longer and take medications for longer periods of time, the number of HIV-related neuropathic pain (HIVNP) sufferers is expected to rise. According to the Center for Disease Control (CDC), there are 957,000 people in the U.S. infected with HIV. As this number of individuals infected undergoing antiretroviral treatment increases, the number of HIVNP sufferers is likely to rise at a similar rate, growing from 145,000 in 2003 to 182,000 in 2010 at a compound annual growth rate of 3.3 percent. Even though it is a niche market, HIVNP represents a significant growth opportunity for smaller pharmaceutical companies since it is not as complicated as DNP and there are currently no treatment options specifically for it. Chart 2.7 shows the prevalence of HIV and HIV-related neuropathic pain in the U.S. from 2000 to 2010.

Trigeminal neuralgia is considered to be a niche area that is well served by generic versions of carbamazepine, so pharmaceutical manufacturers have not been focusing their clinical development efforts on developing a product for it or even obtaining an indication for it. In 2003, 124,600 people in the U.S. were estimated to have suffered from trigeminal neuralgia. This number is projected to grow to 158,500 in 2010 at a compound annual growth rate of 3.5 percent. Chart 2.8 depicts the prevalence of trigeminal neuralgia in the U.S. from 2000 to 2010.

Approximately 1.8 million patients in the United States were on medications for various forms of neuropathic pain in 2003. An estimated 55.9 percent of patients were on anticonvulsants due to the popularity of Neurontin, followed by 23.7 percent on antidepressants, 13.0 percent on opioids, and 7.4 percent on topical analgesics. The introduction of several new products with improved safety profiles, the availability of generic gabapentin in early 2005, and growing awareness is expected to dramatically inflate the number of patients undergoing treatment to 2.9 million by 2010 at a compound annual growth rate of 7.1 percent. The total numbers of patients taking medications are presented in Figure 2-2 and Chart 2.9.

While anticonvulsants are anticipated to remain the major product class used for neuropathic pain due to generic gabapentin and pregabalin, topical medications and emerging therapies such as ruboxistaurin are projected to experience rapid uptake among patients and physicians due to their advancements in side effect profiles and targeted efficacy. Antidepressants should maintain a front-line role in treatment due to their history in clinical practice, while opioids should remain limited to an adjunctive role because of their questionable efficacy against neuropathic pain and safety issues.

The patient forecasts by segment are shown in Figure 2-3 and Chart 2.10. Figure 2-4 and Chart 2.11 depict the percent of patients per segment for the U.S. neuropathic pain medications market from 2000-2010.

The U.S. neuropathic pain medications market is estimated to have generated revenues of around $2.48 billion in 2003. Total market revenues are projected to increase to $4.83 billion in 2010 at a strong compound annual growth rate of 10.0 percent. Figure 2-5 and Chart 2.12 present the revenue forecasts for the U.S. neuropathic pain medications market for the period 2000-2010 with 2003 as the base year.

Anticonvulsants account for 72.4 percent of total revenues in the U.S. neuropathic pain market and are