Those with neuropathic pain get a new treatment choice

February 7, 2005

Every year, approximately 150,000 Americans develop postherpetic neuralgia (PHN), which is often described as a constant stabbing, burning, or electric shock-like sensation.

Every year, approximately 150,000 Americans develop postherpetic neuralgia (PHN), which is often described as a constant stabbing, burning, or electric shock-like sensation.

In addition, approximately half of the 18 million Americans with diabetes develop some form of diabetic neuropathy over the course of their disease, and about one in six diabetes patients develop painful diabetic neuropathy. The pain of diabetic peripheral neuropathy (DPN) is often described as burning, tingling, sharp, stabbing, or pins and needles in the feet, legs, hands, or arms.

Fortunately, the Food & Drug Administration recently approved pregabalin (Lyrica, Pfizer) capsules 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.

The target dose for pregabalin can be reached very quickly, compared with that for gabapentin, said McCarberg. He said that pregabalin is excreted almost solely by the kidney, so that no risk of drug-drug interaction with agents metabolized by the cytochrome p450 system exists.

McCarberg noted that the dose of pregabalin and its concentration in the bloodstream have a linear relationship. As the dose of pregabalin increases, so does the pregabalin concentration in the bloodstream. However, as the dose of gabapentin increases, he said, more and more of the compound is excreted by the kidney. To achieve an optimal dose of gabapentin, McCarberg said, requires a very large dose.

The linear relationship between dose and concentration of pregabalin is advantageous because, unlike gabapentin, pregabalin will not require large doses, McCarberg explained. In addition, clinicians know that as the dose of pregabalin is increased, their patients are getting exactly that much more of the drug than was administered at the last dose.

In studies, pregabalin appeared to have been well tolerated, with an adverse-effect profile similar to that of gabapentin, said R. Keith Campbell, Pharm.D., CDE, distinguished professor of pharmacy at Washington State University College of Pharmacy in Pullman. Campbell said that dizziness, somnolence, dry mouth, peripheral edema, blurred vision, weight gain, and difficulty concentrating occurred more frequently among pregabalin users than among those receiving a placebo during studies.

Pregabalin therapy should be monitored closely in those with cardiovascular disorders because of the risk for peripheral edema, Campbell advised. He also recommended that pharmacists encourage patients, particularly those with diabetes, to find some form of exercise and avoid overeating, in order to avoid weight gain.

Campbell said that with the approvals of pregabalin and duloxetine (Cymbalta, Eli Lilly), two therapeutic options are available for the treatment of PDN, whereas several months ago, no drugs were specifically approved for it. In a statement, Joseph Feczko, president of Worldwide Development at Pfizer, said, "Pregabalin is an important new therapy for millions of people suffering from the two most common neuropathic pain conditions, as it provides rapid and sustained pain relief." The company reported that pregabalin is currently under review by the FDA for the adjunctive treatment of partial seizures in adults. The company is working with the FDA to finalize the labeling for the epilepsy indication.