Question from a Member:
I find some patients increase their dose of gabapentin themselves, and use it as a prn medication when they are highly anxious. What exactly is the research on the potential addictive nature of gabapentin/ pregabalin? I know in some parts of the world it has become a major problem.
Yes, misuse gabapentin or pregabalin (together called gabapentinoids) is, unfortunately, becoming more common, mainly in persons with a history of substance use disorders. These persons often:
1. Take higher than the usual doses
2. Combine gabapentin (or pregabalin) with other substances like opioids, alcohol, quetiapine, etc.
Why do they do it?
Gabapentinoids can reduce anxiety, help with sleep, produce euphoria when used in high doses, and even produce dissociative effects (Evoy et al., 2017). The euphoria and dissociative effects are different from the effects of taking benzodiazepines.
For persons being monitored with urine drug screens, an obvious advantage it that gabapentinoids will not be detected on a standard urine drug screen.
Who is at higher risk?
Such abuse, not surprisingly, is particularly common among those with an opioid use disorder, in whom as many as approximately 10 to 20% may misuse gabapentin (Smith et al., 2016).
Comparing gabapentin to pregabalin
1. Ease of access
Gabapentin is not a controlled substance and is generic. It is, therefore, relatively easily obtainable. Pregabalin is a controlled substance, even though it is classified as Schedule V, the lowest level of abuse potential. Also, since pregabalin is not generic as of February 2017, it is expensive and hard to obtain. This is probably why as of 2017 misuse of gabapentin is more common than that of pregabalin. However, I predict that when pregabalin becomes generic in 2019, there will be a noticeable increase in misuse of pregabalin.
2. Speed of absorption
There is a significant difference in the absorption and bioavailability of gabapentin versus pregabalin.
Peak levels of pregabalin are attained in about one hour which is three-times faster than with gabapentin (Bockbrader et al., 2010). As we know, the speed of onset of effect is usually correlated with the addiction potential of a drug of abuse.
If a person takes a high dose of pregabalin in order to abuse it, more than 90% gets absorbed. On the other hand, the absorption of gabapentin is saturable. For example, if a person takes 300 mg of gabapentin, 68% is absorbed but if 1600 mg is taken, the absorption is reduced to 36% (Evoy et al., 2017).
While euphoria was described as a relatively common adverse event in clinical trials of pregabalin, it was not reported in clinical trials of gabapentin at usual doses.
Pregabalin has higher potency, a quicker absorption rate, and greater bioavailability than gabapentin (Schifano, 2014) and, perhaps, a greater tendency to produce euphoria. All these suggest that, at least theoretically, the abuse potential of pregabalin may be greater than that of gabapentin.
Dependence and withdrawal
Gabapentinoids can also result in physical dependence and a withdrawal syndrome, including in neonates exposed to gabapentin (e.g., Carrasco et al., 2015).
1. In my experience, persons with substance use disorders may abuse ANYTHING that is sedating or makes them feel better temporarily.
2. When a medication for anxiety or insomnia is essential, we often have to choose between the lesser to two evils.
3. We should watch for misuse of gabapentin and pregabalin, especially pregabalin and especially in persons who have a history of substance use disorder.
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