Alcohol and other CNS depressants (sedatives, benzodiazepines, opioids) increase drowsiness, QT-prolonging medicines (e.g., amiodarone, sotalol, some antipsychotics, macrolide/fluoroquinolone antibiotics), anticholinergics (may increase dry mouth/constipation/urinary retention), MAO inhibitors (additive anticholinergic/CNS effects)