Gabapentinoids in Ireland (2010-2020): trends in prescribing, law enforcement drug seizures & post-mortem toxicology

Background: The gabapentinoids, pregabalin and gabapentin, were initially considered to have low abuse potential. However, concern regarding misuse, diversion, and dependence is growing. There is no single source of information that fully describes the situation in Ireland. We examined 5 different data sources to explore trends in: (1) gabapentinoid prescribing in the community (national pharmacy claims database 2010- 2020) and prisons (pharmacy dispensings 2012-2020), (2) illicit supply of gabapentinoids using law enforcement drug seizures data (2012- 2020), and (3) detection of gabapentinoids in a national postmortem population (2013- 2020).
Methods: Gabapentinoid prescribing rates per 100 000 eligible community population / per 1,000 prison population, annual number of drug seizures involving gabapentinoids, and gabapentinoid detection (positive) rates per 100 postmortem toxicology case were calculated. Negative binomial regression models were used to evaluate longitudinal trends for gabapentin and pregabalin separately.
Results: Gabapentin (adjusted rate ratio [ARR] 1.06, 95% confidence interval [CI] 1.05–1.06, P < .001) and pregabalin (ARR 1.08, 95% CI 1.08–1.09, P < .001) prescribing increased annually in the community, with higher rates of pregabalin (vs. gabapentin) observed every year. Pregabalin and gabapentin prescribing also increased in prisons (2012-2020), with higher rates of pregabalin prescribing. Drug seizures involving pregabalin also increased (RR 1.54 95% CI 1.25–1.90, P < .0001), but not gabapentin. Of the 26,317 postmortem toxicology cases, 0.92% tested positive for gabapentin, and 6.4% for pregabalin. Pregabalin was detected more often than gabapentin each year, with the number of pregabalin positive cases increasing from 2.3% in 2013 to 7.5% in 2020  (RR 1.13, 95% CI 1.11–1.48, P < .001).  A total of 1,901 cases (7.2%) tested positive for heroin/methadone; this sub-group had a higher detection rate for pregabalin (n = 528, 27.8%) than gabapentin (n = 41, 2.2%), with a high burden of co-detections for pregabalin with benzodiazepines (peaking at 37% in 2018), and pregabalin with prescription opioids (peaking at 29% in 2020).
Conclusion: This study raises concerns regarding the increasing availability of gabapentinoids, particularly pregabalin, including a growing illicit market, and the potential for serious harm arising from poly drug use involving pregabalin among people who use heroin or methadone. People using gabapentinoids with opioids need to be made aware that naloxone does not reverse respiratory depression caused by pregabalin or gabapentin. Policy makers should consider reclassifying gabapentinoids as a controlled drug, particularly pregabalin. However, learning from the Scottish overdose crisis involving benzodiazepines, any policy decisions regarding pregabalin in Ireland will need to consider not only the question of supply but also demand. Effective deprescribing interventions for gabapentinoids are needed.