Pregabalin, a drug that binds to calcium channels in the central nervous system, was approved by the Food and Drug Administration for the management of pain associated with postherpetic neuralgia in late December 2004.
There are now three FDA-approved treatments for this indication; the others are gabapentin (Neurontin) and the 5% lidocaine patch. The FDA also approved pregabalin for the pain associated with diabetic neuropathy.
The approvals were based on six placebo-controlled, double-blind studies–three in patients with postherpetic neuralgia. The studies showed the drug provided quick and clinically meaningful reductions in pain in a significant proportion of patients, according to Pfizer, which will market pregabalin under the trade name Lyrica.
For postherpetic neuralgia, “the time course to pain relief will be much quicker” than with treatments such as tricyclic antidepressants. Pregabalin also has a narrow dose range, which will make it easier to prescribe than gabapentin, which has a “huge” dose range because of variable absorption across the GI tract, said Brett R. Stacey, M.D., one of the trial investigators.
Like gabapentin, pregabalin binds to a specific subunit of one of the calcium channels, but pregabalin “appears to bind more avidly” than gabapentin, said Dr. Stacey, medical director of the comprehensive pain center at Oregon Health and Science University, Portland. The time to onset of pain relief can begin the day after treatment is started, he added.
Side effects have been tolerable and not hugely problematic and are the same as with other CNS drugs; sedation and dizziness are two of the most common ones reported by patients, Dr. Stacey said.
Pregabalin is not yet available. It is expected to be classified as a controlled substance in a category with lower potential for misuse or abuse, compared with other controlled substances, according to Pfizer. A company spokesperson said the Drug Enforcement Administration is reviewing the classification, and until that decision is made, pregabalin will not be available. But Pfizer expects it to become available “in the near future.”
The recommended dosage for pain after shingles is 150–300 mg per day, given in two or three doses; the dosage can be increased up to 600 mg per day, based on tolerability, if patients do not experience sufficient reductions in pain, according to the spokesperson.
Dr. Stacey has done research for Pfizer and has been a consultant to the company for gabapentin and pregabalin.