Gabapentin and pregabalin misuse are problems that are not going to go away. My post on gabapentin is one of the most-read on this site. While these are useful medicines, workers in drug treatment and support see patients regularly on gabapentin or pregabalin who have misused the drugs or who are misusing them. Guidance is to avoid these in folk with a history of substance dependence. Guidance, it seems, is not being followed.
A paper in CNS Drugs by Prof. Fabrizio Schifano at the University of Hertfordshire takes a closer look. Awareness of the issues and the problems arising is increasing:
- The drugs are widely prescribed in neurology, primary care and psychiatry
- Prescription volumes are rising
- Increasing reports of misuse are coming through
- Fatalities are being reported
How do they work?
Prescribed for nerve pain or epilepsy (and less commonly for anxiety) they ‘soothe’ nerves by working on GABA systems, but may also indirectly influence the dopamine reward pathway. Both pathways could explain their potential for misuse. Users may take 3-20 times the recommended dose, chasing an effect which can include ‘euphoria, improved sociability, and a marijuana-like high/relaxation.’ Stopping abruptly can cause withdrawal, including ‘insomnia, nausea, headache or diarrhoea.’
- In the UK… pregabalin and gabapentin prescribing has increased, respectively, by 350 and 150 % in just 5 years
- There is an anecdotally growing black market, with gabapentinoids being allegedly available without prescriptions through online pharmacies
- Pregabalin and gabapentin first emerged in the UK mortality databases in 2006 and have shown an increasing trend since then in respect of being implicated in death
- Most gabapentin victims (e.g. two-thirds in 2012) were not being prescribed the drug
- In a Swedish analysis of almost 50,000 patients who had received three or more gabapentin prescriptions, a third had a history of drug misuse
- In a Scottish survey of drug clinic patients 22% (29/129) admitted to using gabapentin or pregabalin
Prof Schifano points out that these drugs may be safer for non-addicted populations than other medications that are available. He also notes that although gabapentin and pregabalin received licenses in Northern America in 2005, the debate around misuse did not appear in the literature until 2010 and this lag mirrors the pattern with other ‘safe’ drugs like benzodiazepines. The reason for this may be in how trials are set up with carefully controlled dosing. Such trials typically exclude substance misusers. The Prof explains:
As a consequence, the real potential of misuse of the index molecule will be more properly appreciated only when a large number of clients, who will involve vulnerable individuals, are exposed to the drug.
Doctors need to be aware of the risk and cautious in prescribing and in withdrawing patients from the drug. They should ‘carefully evaluate a possible previous history of drug abuse’ and they need to be able to quickly identify problem use. But there is much more to be done:
The epidemiology of gabapentinoid misuse needs further detailed and urgent assessment, and consideration of gabapentin/pregabalin testing in urine drug screens should be routinely considered. Further empirical studies with gabapentinoids should be encouraged, focusing on a better assessment of their addictive liability levels across a range of dosages and in individuals with a previous substance misuse history.
Schifano, F. (2014). Misuse and Abuse of Pregabalin and Gabapentin: Cause for Concern? CNS Drugs, 28 (6), 491-496 DOI: 10.1007/s40263-014-0164-4