The study used a within-individual design that compared when a person was taking a gabapentinoid with when he or she was not. During treatment periods, participants were at increased risk of suicidal behavior or death from suicide (age-adjusted hazard ratio, 1.26), unintentional overdose (1.24), head or body injuries (1.22), and road traffic incidents or offenses (1.13). Associations with arrests for violent crime were not significant.
Gabapentinoid treatment was associated with increased hazards of suicidal behavior in people young than 55 years, but hazards were reduced or not significant in participants aged 55 years and older. Participants aged 15-24 years had the highest hazards of suicidal behavior (1.67).
In a sensitivity analysis, the researchers examined participants who had a diagnosis of comorbid epilepsy, psychiatric disorders, or musculoskeletal disorders before the start of gabapentinoid treatment. Among patients with comorbid epilepsy, gabapentinoids were not significantly associated with suicidal behavior and were associated with reduced hazards for all other outcomes.
“In comorbid psychiatric disorders, gabapentinoids were associated with lower risk for all outcomes,” the researchers said. Among patients with comorbid musculoskeletal disorders, gabapentinoids were associated with reductions in head or body injuries, traffic incidents, and arrests for violent crime.
Dr. Molero and her associates noted that they lacked information about alcohol and drug use, as well as treatment adherence and the conditions for which gabapentinoids had been prescribed. Furthermore, differences in prescription practices and outcome rates might affect the generalizability of the results to other countries.
The different results for pregabalin and gabapentin “could be due to their different pharmacodynamic and pharmacokinetic profiles; pregabalin has a higher potency, greater bioavailability, and quicker absorption than gabapentin. Pregabalin also has been associated with withdrawal symptoms following rapid discontinuation, which could be related to suicidal behavior,” Dr. Molero and colleagues said. “The reduced hazards in older people could reflect pharmacodynamic differences related to age, less concurrent use of alcohol or drugs, different indications for treatment, or reduced symptom severity of underlying conditions.”
The Wellcome Trust, Swedish Research Council, and Karolinska Institute supported the study. The authors had no disclosures relevant to the study. One author reported grants from Shire and Evolan and has served as a speaker for Shire.
SOURCE: Molero Y et al. BMJ. 2019 Jun 12. doi: 10.1136/bmj.l2147.