Or might there be some obscure pharmacologic mechanism? This paper tries to compare the pharmacology of the two drugs. Is this just an illusion? Is it my bias? If a patient reports feeling dizzy on high-dose gabapentin, do I say “Yeah, you’re on a really high dose, I’m not surprised you feel that way, let’s back off?” And then if they feel the same thing on low-dose pregabalin, might I say “It’s a low dose, you’re just getting used to the medication, give it a few more weeks”? Might my biases even be affecting how patients report their own experiences? I usually avoid higher gabapentin doses because I feel like they have more side effects than low pregabalin doses. Maybe all our gabapentin doses are just too low. If this forms a reference point in the doctor’s mind, then maybe what we think of as a “high dose” of gabapentin is the same as what we think of a “low dose” of pregabalin. This dosing table suggests 1 mg pregabalin = 5 mg gabapentin, so 300 mg of pregabalin = 1500 mg gabapentin! So we’re starting gabapentin patients on less than half as much medicine as we start pregabalin patients on. But it recommends 100 mg three times a day = 300 mg of pregabalin. UpToDate recommends treating anxiety disorders with gabapentin using a starting dose of 300 mg twice a day = 600 mg daily. One possibility is that we’re getting the doses wrong. For now, the apparent difference between pregabalin and gabapentin is one of the great mysteries of life, one of the things that makes me doubt my own sanity. Although studies confirm pregabalin is great for anxiety, nobody has done the studies on gabapentin that would let me compare it. Am I imagining a difference betwee these two supposedly-similar medications? I don’t know. I’ve never had patients with more than minimal anxiety happy on gabapentin alone. Still, I have to wonder – why am I sitting around waiting when I could just give people gabapentin? Confirmed pharmacodynamically-identical, generic, and cheap? The answer is, gabapentin doesn’t seem to work that well. I can’t use it too often, because of the price, but I’m really excited about the upcoming generic version coming out so I can use it more often. They can’t stop talking about how great it is. And a lot of scientists have analyzed pregabalin and said it’s definitely just doing the same thing gabapentin is.īut some of my anxiety patients swear by pregabalin. This kind of thing is endemic in health care and should always be the default hypothesis. The gabapentin patent was running out, so Pfizer synthesized a related molecule that did the same thing, hyped it up as the hot new thing, and charged 50x what gabapentin cost. On the face of things, pregabalin seems like another Big Pharma ploy to extend patents. Pregabalin officially went generic last month, but isn’t available yet in generic form, so you’ll have to pay Pfizer $500 a month. I haven’t had much luck finding patients a dose that works well but doesn’t have these side effects, which is why I don’t use gabapentin much. At the high end, it can cause sedation, confusion, dependence, and addiction. Most doctors (including me) use it at the low end, where it’s pretty subtle (read: doesn’t usually work). It has an unusually wide dose range: guidelines suggest using anywhere between 100 mg and 3600 mg daily. It’s commonly used for seizures, nerve pain, alcoholism, drug addiction, itching, restless legs, sleep disorders, and anxiety. Two gabapentinoids are approved by the FDA: gabapentin (Neurontin®) and pregabalin (Lyrica®). Although they were developed to imitate GABA’s action, later research discovered they acted on a different target, the A2D subunit of calcium channels. The gabapentinoids are a class of drugs vaguely resembling the neurotransmitter GABA.