Association between gabapentinoid treatment, concurrent use with opioid or benzodiazepine and the risk of drug poisoning: A self-controlled case series study

Background Consumption of gabapentinoids has increased worldwide in recent years, and the association between its use and drug poisoning is of public health concern. This study aimed to investigate the association between gabapentinoid treatment and the risk of drug poisoning. Methods and findings In this within-individual study, we utilised data from the United Kingdom (UK) Clinical Practice Research Datalink (CPRD) Aurum database linked to the Hospital Episode Statistics (HES) and Office for National Statistics (ONS). The analysis included individuals aged 18 or above who were prescribed gabapentinoids and had an incident all-cause drug poisoning event between 1st January 2010 and 31st December 2020. Using the self-controlled case series (SCCS) design, we assessed the risk of drug poisoning incidence in predefined risk periods: 90 days before treatment initiation, first 28, 29–56, 57–84 days, and the remaining treatment time. Concomitant use with opioids/benzodiazepines was also evaluated. Adjusted incidence rate ratios (aIRRs) were calculated using conditional Poisson regression. A case-case-time-control (CCTC) analysis was also conducted, with adjusted odds ratio (aOR) calculated to validate the findings from the main SCCS analysis. All analyses have adjusted for key time-varying confounders, including age, season, and concomitant use of opioids, antiseizure medications, psychotropic medications, and non-steroidal anti-inflammatory drugs (NSAIDs). 16,827 individuals met the inclusion criteria and were included in the SCCS analysis. The risk of drug poisoning, compared with the reference periods, increased during the first 28 days of gabapentinoid treatment (aIRR = 1.81, 95% confidence interval CI 1.66, 1.99; p < 0.001), eventually dropped to 1.11 (95% CI 1.05, 1.17; p < 0.001) in the remainder of the treatment period. Notably, the risk was doubled during the 90-day preceding treatment initiation (aIRR = 2.09, 95% CI 1.98, 2.21; p < 0.001). Co-administration with opioids elevated the risk by 30%, while benzodiazepines increased it 2-fold. The CCTC analysis also detected an increased aOR of 1.36 (95% CI 1.12, 1.65; p = 0.002) of receiving gabapentinoid treatment within 30 days prior to a drug poisoning event. The SCCS approach cannot completely exclude the effect of unmeasured time-varying confounders, such as transient changes in socioeconomic status, major life events, or illicit drug use, although the negative control analysis did not suggest meaningful residual confounding. Conclusions The results suggest that gabapentinoid is associated with an increased risk of drug poisoning. Close monitoring throughout gabapentinoid treatment journey for drug poisoning is needed, especially at the initial phase. Concomitant use with opioid or benzodiazepines should be avoided.