Antihistamines as a common cause of new-onset seizures: a single-center observational study

Scarce data are available regarding the proportion of drugs that have provoked new-onset seizures. The aim of this study was to investigate the types of causative drugs of drug-induced new-onset seizures in a relatively large population of patients who were admitted to our epilepsy monitoring unit.

Using a hospital-based database, patients with new-onset seizures were selected and the underlying etiology of new-onset seizures was reviewed. Based on the etiologic conditions, acute symptomatic seizure was classified into 7 groups of provocation factors: drug, alcohol, encephalitis, stroke, hypoxic injury, metabolic, and unclassified. Causative drugs for new-onset seizures were further investigated.

Altogether, 363 patients with new-onset seizures were reviewed in this study. The most common cause of new-onset seizures was epilepsy, followed by syncope, acute symptomatic seizure, and others. Drugs were found to be the most common provocation factor for acute symptomatic seizures. The most common causative drug was antihistamine, followed by stimulants, antibiotics, and other drugs. Most patients with antihistamine-induced seizures had normal renal function and were under treatment at the therapeutic dose.

In our population, antihistamine accounted for the highest proportion of drug-induced seizures. Considering that antihistamines are widely used as over-the-counter drugs around the world, they should be considered a possible cause of new-onset seizures.