Medicine Use Preceding Fatal Poisonings Among Individuals With Bipolar Disorder

Pharmacotherapy may reduce overall suicide risk in bipolar disorder, but prescribed medicines can also be causative agents in suicidal and accidental poisonings. This nationwide, nested case-control study utilized data from several national registers in Finland in 1996-2018. In a cohort of 60 045 individuals aged 15-65 with bipolar disorder, cases with fatal poisoning due to medicines or illicit substances were matched by age and sex to four controls each. The association between fatal poisoning and medicine use in the prior 2 weeks was examined using conditional logistic regression. The 777 (1.3%) cases who died of poisoning due to medicines or illicit substances during the study period were matched to 3108 controls. Of cases, 56.5% (n = 439) died of a suicidal poisoning and 38.4% (n = 298) of an accidental poisoning. After adjusting for sociodemographic characters, comorbidities and other medicine use, tricyclic antidepressants (aOR 3.07, 95% CI 2.09-4.50), gabapentinoids (3.05, 2.08-4.47), opioids (2.65, 1.88-3.75), benzodiazepines (2.13, 1.71-2.64), Z-drugs (2.19, 1.66-2.88) and antipsychotics (1.94, 1.56-2.40) were associated with fatal poisonings. While the associations may reflect clinical severity of the disorder among users of these medicines, increased caution is warranted when prescribing them to individuals at elevated risk of poisoning.