Background: Seizures are uncommon, but serious, adverse effects of antidepressant drugs. A better understanding of drug-related seizure risk, its predictors, and its neurophysiologic basis might help clinicians avoid this adverse event. A better understanding of the factors involved in the determination of seizure risk would be helpful for interpretation of seizure rates reported.
Method: The authors review case reports, series of cases, and information from clinical trials of antidepressants to determine antidepressant-related seizure risk. Predisposing factors are identified. Effects of dose, blood levels, and duration of treatment on seizure risk are examined. Electrophysiologic and in vitro models of drug-related seizure induction are discussed.
Results: A significant proportion of drug-related seizures occurs in individuals with an identifiable predisposition, such as previous seizures, sedative or alcohol withdrawal, and multiple concomitant medications. Seizure risk for most antidepressants increases with dose (or blood level), and comparisons between drugs should consider seizure rates at the effective dose (or blood level) for each drug. For imipramine, the most frequently studied tricyclic, the literature indicates a seizure rate between 0.3% and 0.6% at effective doses. In unselected patients and at higher doses, these rates may be higher. Fluoxetine, sertraline, fluvoxamine, trazodone, nomifensine, and the monoamine oxidase inhibitors have a lower seizure risk. Estimates for recently marketed antidepressants with intermediate seizure risk are complicated by the fact that effective doses and blood levels are not well established.
Conclusion: Assessment of seizure risk in individuals involves consideration of predisposing factors, the antidepressant selected, and the bioavailability of the drug. Future studies of seizure risk would benefit from the use of specified criteria for determination of probable seizure events, a priori definition of predisposing exclusions, samples sufficiently large to provide adequate power, blood level monitoring, and inclusion of duration of drug treatment in the calculation of risk.