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Fibromyalgia Basics

Gabapentin vs. Pregabalin
What’s the Difference?

Gabapentin and pregabalin both work to increase the amount of GABA (a pain-fighting transmitter) in your central nervous system, but there are differences between them. For starters, gabapentin has been on the market ten years longer and it is cheaper. So, if your doctor prescribes pregabalin because it is “FDA-approved” for fibromyalgia, your insurance company may claim it is no different than the less expensive gabapentin. Or, maybe your insurance policy will allow pregabalin if you are willing to stomach the higher price.

Is it worth paying more for pregabalin than what you might pay for the same dose-equivalent of gabapentin? Unfortunately, neither drug has ever been tested against the other in a head-to-head comparison even though they are made by the same company, Pfizer. So, the next-best thing is an analysis of the data from clinical trials comparing the effectiveness of each drug for treating fibromyalgia as well as its side effect profile.*

The research team who did the comparison found that both drugs were unimpressive. That being said, they found some differences between the two medications.

For every five patients trying gabapentin, only one will find it reduces pain by at least 30 percent. The number of patients that must be treated for one person to show improvements on pregabalin is eight. In general, for a drug to be successful, the researchers state that it should work in one out of every two to four patients.

Despite the low treatment rate, you could still be the one person who does respond to either of these medications. So, are there any differences with their side effects? Yes. At doses between 1,200 and 2,400 mg/day, gabapentin is more likely to cause headaches and sedation. At doses between 300 and 450 mg/day, pregabalin is more likely to produce dizziness and weight gain.

Gabapentin appears to be slightly more helpful for treating fibromyalgia, but the side effects of the two drugs could be your deciding factor.

Pregabalin More Regulated

The Drug Enforcement Agency (DEA) decided to place more regulations on pregabalin by making it a schedule V (or 5) medication. Gabapentin is not regulated by the DEA, but seven states in the U.S. have passed laws that regulate this drug as a schedule V controlled substance. These states are AL, KY, MI, ND, TN, VA, and WV.

Your physician (or nurse practitioner in some states) must have a current DEA license to prescribe pregabalin. Your provider will probably require that you see them at least annually. There may be other restrictions based on the laws of the state you reside in.

Overall, schedule V carries the lowest potential for abuse of the drugs that are scheduled by the DEA. But why would pregabalin be regulated by the DEA, while gabapentin is not, given that they are in the same class of medications? The answer may have to do with the timing of the FDA trials.

Gabapentin was approved ten years before pregabalin and the FDA had fewer testing requirements in the 1990s. When pregabalin was up for approval, it had to be tested on known drug abusers to determine if abusers felt better after taking this medication than healthy controls. The drug made the addicts less anxious by a margin of about 5 percent, and this is why the DEA stepped in to regulate it as a schedule V drug.

Considering that people with fibromyalgia pain could use an agent that keeps them calm, the anti-anxiety properties of pregabalin might be welcomed. However, this finding in addicts led the DEA to put more regulations on the medication. As for gabapentin, there have been reports of this drug being abused (especially by addicts) and this has led to certain states placing more regulatory scrutiny on it.

Will your doctor deny you a script for pregabalin because of a schedule V labeling? Probably not. But you should be aware that your insurance company may regulate your prescription refill requests in a more restrictive manner. For example, they may not allow 90-day supplies even if your state does. So your insurance company, not necessarily your physician, may make a script for pregabalin more of a hassle.

If you are wondering why you must take a higher dose of gabapentin as opposed to pregabalin, it’s because the gabapentin molecule weighs four times more. If you need to go off either of these medications, you need to do it slowly to avoid a flare up of your symptoms (i.e., you will get withdrawal symptoms). Even if you don’t think the medication is helping, do not discontinue it abruptly. Also, both drugs are metabolized by your kidneys, so it you have serious renal impairment, talk to your kidney specialist before trying either drug.

* Siler AC, et al. J Pain 12(4):407-415, 2011.