On pins and needles: Latest therapies give R.Phs.s the tools they need for better management of neuropathic pain

June 20, 2005

Neuropathic pain (NP) is a condition that is more common than has generally been recognized. Patients often report a pain in their extremities akin to being on pins and needles. It is estimated that in the United States, more than three million people have diabetic peripheral neuropathy (DPN) and as many as one million have postherpetic neuralgia (PHN). Luckily, newer drugs such as duloxetine (Cymbalta, Eli Lilly) and gabapentin (Neurontin, Pfizer) have proven efficacious for providing relief.

Neuropathic pain (NP) is a condition that is more common than has generally been recognized. Patients often report a pain in their extremities akin to being on pins and needles. It is estimated that in the United States, more than three million people have diabetic peripheral neuropathy (DPN) and as many as one million have postherpetic neuralgia (PHN). Luckily, newer drugs such as duloxetine (Cymbalta, Eli Lilly) and gabapentin (Neurontin, Pfizer) have proven efficacious for providing relief.

The investigators found that mean daily pain (on a scale of 0 to 10, with higher numbers indicating more severe pain) was 5.72 at baseline, 4.49 with placebo, 4.15 with gabapentin, 3.70 with morphine, and 3.06 with the combination of gabapentin and morphine.

This approach is called "rational polypharmacy," said Steven Stanos, D.O., medical director, Chronic Pain Care Center at the Rehabilitation Institute of Chicago, because clinicians can target the medications to the different neurotransmitters and receptors that become upregulated in those with NP.

Drugs now available Last September, the Food & Drug Administration approved duloxetine capsules for the treatment of DPN. Duloxetine is a potent serotonin and norepinephrine reuptake inhibitor, as well as a less-potent dopamine reuptake inhibitor, said John Greist, M.D., a clinical professor of psychiatry at the University of Wisconsin-Madison Medical School. The inhibition of norepinephrine reuptake is important for the relief of pain, he added.

Getting on the schedule The FDA approved pregabalin (Lyrica, Pfizer) capsules last December for the management of neuropathic pain associated with PHN and DPN. Pregabalin is the first drug to receive FDA approval for both of these indications.

Pfizer expects to launch the drug sometime this year. Unfortunately, the launch will be delayed while pregabalin undergoes controlled-substance scheduling at the Drug Enforcement Administration. In a statement, the company said that "Lyrica is expected to be classified as a controlled substance in a category with lower potential for misuse or abuse relative to controlled substances in other categories."

Pregabalin is an alpha-2 delta ligand that acts on voltage-gated calcium channels, explained Bill McCarberg, M.D., founder of the Chronic Pain Management Program for Kaiser Permanente in San Diego.

The recommended dosing range of pregabalin will likely be from 300 mg/day to 600 mg/day.

Other treatment options In addition to gabapentin, other first-line therapies for NP are tricyclic antidepressants (TCAs), the lidocaine (LidoSite Topical System Kit, Vyteris; Lidoderm, Endo) 5% patch, opioids, and tramadol, said Berdine.