|Pregabalin and Gabapentin for Neuropathic Pain and CRPS
By Brett R. Stacey, MD, and Pamela Campbell, MD
Comprehensive Pain Center, Oregon Health & Science University,
Recently, pregabalin (Lyrica®) was approved by the Food
and Drug Administration (FDA) for the treatment of post herpetic
neuralgia (PHN) and painful diabetic peripheral neuropathy
(DPN). Pregabalin has a chemical structure similar to gabapentin
(Neurontin®), a medication originally developed to treat
seizures that is now widely used to treat many varieties of
neuropathic pain including CRPS. Both medications reduce
pain by normalizing overactive pain pathways. Pregabalin is
the first drug ever approved in the United States for two
different neuropathic pain conditions. We believe it will
be an important treatment option for many patients with CRPS.
Gabapentin has been a great advance in treating CRPS and
neuropathic pain. In addition to its effectiveness, it is
very safe, with no reports of fatal overdose or organ failure.
However, it does not work for everyone and sometimes the side
effects are very bothersome. Does pregabalin offer an improvement?
There are currently at least six large studies with pregabalin
for the treatment of PHN and DPN. In these studies pregabalin
shows up to a 50 percent decrease in pain scores. This is
better than the roughly 30 to 40 percent reduction in pain
scores observed in the trials of gabapentin for the same indications.
In addition to pain relief, patients treated with pregabalin
report improvements in sleep, mood, and day-to-day function.
Because of its longer half-life, pregabalin can be dosed on
a twice a day schedule. (Gabapentin is dosed three times a
day.) At high doses, much of the gabapentin is never absorbed
from the bowel, whereas pregabalin is easily absorbed at all
doses, making for more predictable dosing. Data suggest that
pregabalin can begin reducing pain as quickly as one day after
it has been started. This is quicker than ever reported with
gabapentin. Finally, preliminary results from a study of patients
with neuropathic pain who had not responded to gabapentin
and two other medicines shows that even in those patients,
pregabalin can provide significant relief. The majority of
patients in this study (who had PHN and DPN) strongly preferred
pregabalin to gabapentin.
In addition to neuropathic pain, pregabalin has been shown
to be effective in fibromyalgia pain, the pain after spinal
cord injury, and anxiety.
Pregabalin comes in 8 dosage strengths from 25mg up to 300mg.
All capsule sizes are the same price Roughly 1,800 mg of pregabalin
is approximately $90, while pregabalin twice a day for all
doses is around $118.
Gabapentin and pregabalin have similar side effects. The most
common are dizziness and sedation. Patients placed on gabapentin
usually experience side effects as they titrate slowly up
to an effective dose, which is roughly 1,200 to 3,600 mg per
day. Conversely, for patients taking pregabalin the typical
starting dose of 150 mg per day can be helpful.. The range
of effective doses is 150 to 600mg per day. For both medications,
side effects tend to decrease over time. Less common side
effects include peripheral edema and weight gain especially
when taken in combination with oral hypoglycemics.
Pregabalin is categorized by the FDA as a schedule V drug,
the lowest level of surveillance from the FDA. This means
it is a controlled substance.
The earliest reports of gabapentin's use in treating pain
were case reports of a few patients with CRPS who improved
with gabapentin. Unfortunately, there have never been larger,
controlled studies that definitively prove the benefits of
gabapentin. As of yet, there are no studies in CRPS for
pregabalin. CRPS and all other nerve pathology other than
PHN and DPN are considered off label since studies in nerve
pain have only been done in these specific conditions.
Our clinical experience
Here at Oregon Health & Science University, we have 8
years of research experience with pregabalin and since September
of 2005 many of our patients have received it. Almost every
patient converted to pregabalin from gabapentin prefers pregabalin
either because of improved pain control or fewer side effects.
Some patients have pain relief immediately. As everyone reading
this knows, treating neuropathic pain is challenging, so pregabalin
certainly doesn't work for everyone. Our experience coupled
with the extensive research supporting its use in other painful
conditions makes us optimistic that pregabalin will prove
to be a valuable tool in treating CRPS.
Updated August 14, 2006