Gabapentin as a first line treatment of spinal cord injury-related neuropathic pain

DailyUpdates 5^th May: As the battle lines are drawn up between gabapentin and its generic equivalents, research published by Turkish researchers suggests that the first-line use of these therapeutics in the treatment of neuropathic pain associated with spinal cord injury will represent one battle in the war between Pfizer and its competitors.

Approximately 26 million patients worldwide (10 million in the ) suffer from some form of neuropathic pain, spending an estimated $2-3 billion annually on treatments. This condition is associated with a variety of etiologies and precipitates other serious pathologies such as depression. The lifestyle of patients can be severely impeded, a problem compounded by the lack of efficacy and frequent incidence of side effects associated with current treatment options (Click here for a full analysis of the neuropathic pain market).

Pfizer's Neurontin (gabapentin) has been hugely successful in the neuropathic pain market generating $2.2 billion in sales and representing 4% of the companies revenues.  However the lack of public awareness, poor physician education, and regional variations in drug availability has meant that gabapentin and other effective drugs are under-utilized.  This along with increasing challenge from generics is putting a squeeze on Neurontin.

Only last week it was announced that Alpharma, who is in litigation with Pfizer over the patent to Neurontin, have agreed to jointly market generic versions of Neurontin with Teva. This agreement will facilitate the sale of Neurontin(R) Tablets and Neurontin(R) Capsules which already generates $2 billion in sales of over $2 billion. Alpharma holds a final ANDA approval for its gabapentin capsules and is awaiting final ANDA approval for the tablets. Teva Pharmaceuticals currently holds tentative approvals for both the tablets and the capsules.

Aggressive promotional campaigns and astute marketing and product positioning strategies will ensure branded products can dominate the neuropathic pain market. With generic gabapentin entering the market, more than ever companies need to be innovative to effectively define and ‘own’ a market and several ways of differentiating a new product from gabapentin are highlighted in LeadDiscovery’s current feature (“Neuropathic Pain Insight - Life Beyond Gabapentin”).

It has been predicted that the neuropathic market will continue to grow unabated over the next ten years primarily due to increased public and physician awareness. Turkish researchers have recently shown that gabapentin should be used as a first line treatment of neuropathic pain associated with spinal cord injury and this data may help drive this growth.

A quarter of a million Americans are currently living with spinal cord injuries and the cost of managing the care of these patients approaches $4 billion each year. Pain is a common complication in these patients with studies suggesting that between 30 to 90% of individuals experience pain after their injury. Finding a way to manage pain is one of the most important research concerns among individuals with spinal cord injury.  Thus neuropathic pain associated with spinal cord injury represents a major component of the total neuropathic pain market.

"Neuropathic pain associated with spinal cord injury is quite refractory, and current treatments are not effective," write Funda Levendoglu, MD, and colleagues from , Meram School of Medicine, in . Despite gabapentin’s position as a treatment of choice for neuropathic pain, its place in the treatment of spinal cord injury-related neuropathic pain has not been well studied.

In their recent clinical study published in the April edition of the journal Spine, the Turkish group enrolled 20 paraplegic patients into a double-blind, crossover-design trial. Seven patients were women and 13 were men. All had complete spinal cord injury at the thoracic or lumbar level and neuropathic pain for more than six months. Age range was between 20 and 65 years.

Patients underwent four weeks of medication/placebo titration, followed by a four-week stable dosing period at maximum tolerated doses, a two-week washout period, then a crossover of four weeks of medication/placebo titration, and finally another four weeks of stable dosing.

All patients completed the study. Gabapentin treatment was associated with decreased intensity and frequency of pain; relief of all neuropathic pain descriptors except for the itchy, sensitive, dull and cold types; and improved quality of life.

Adverse effects occurred in 65% of patients receiving gabapentin treatment and in 25% of those receiving placebo treatment, but these did not lead to study withdrawal and were easily managed by cutting back one step on the dose. In clinical practice, the authors also recommend starting at a low dose and slowly titrating upward.

"Gabapentin can be added to the list of first-line medication for the treatment of chronic neuropathic pain in spinal cord injury patients," the authors write. "It is a promising new agent and offers advantages over currently available treatments."  Positioning of gabapentin or its generic equivalents in the unmet and large sub-class of spinal cord injury patients may therefore have significant effects on the dynamics of the overall neuropathic pain market.

Source DailyUpdates 5^th may; for a full abstract of the original papers see Spine. 2004 Apr 16;29(7):743-51 .

Recommended further reading:

• Neuropathic Pain - Comparative Overview of Treatment Preferences Across the Seven Major Markets
• Neuropathic Pain Insight - Life Beyond Gabapentin
• Pain Therapeutics - Drugs, Markets and Companies
• Cancer Pain - Physician Awareness and Novel Drug Delivery Will Drive Market Opportunities
• Future pain drugs

In this edition of DailyUpdates, LeadDiscovery also highlights a nitric oxide-releasing salbutamol that elicits potent relaxant and anti-inflammatory activities... hyperinsulinaemia and increased risk of breast cancer…the combination of Paclitaxel and nitric oxide as a novel treatment for the reduction of restenosis...and much more.