Sialorrhea possibly associated with bupropion: a case report and review of potential mechanisms

Background Bupropion is typically associated with xerostomia (dry mouth) rather than increased salivation. However, its prescribing information lists “increased salivation” as an infrequent adverse reaction. Case presentation We report the case of a 59-year-old female patient with the diagnosis of comorbid anxiety and depressive disorders. The patient experienced no sialorrhea while on a combination of venlafaxine and low-dose quetiapine. However, after switching venlafaxine to bupropion, she developed significant sialorrhea. The sialorrhea was severe: she had to carry tissues and a plastic bag during the day, and at night the pillow was frequently soaked. Gradual discontinuation of quetiapine did not resolve the symptom. The sialorrhea completely remitted only after bupropion was discontinued and replaced with escitalopram. The Naranjo Adverse Drug Reaction Probability Scale score was 6, indicating a “probable” relationship. Conclusion This case suggests that bupropion may induce sialorrhea, potentially through a synergistic mechanism involving noradrenergic pathways when combined with quetiapine. Clinicians should be aware of this rare adverse effect when prescribing bupropion, particularly in combination therapies. Therapeutic drug monitoring and clinical pharmacist collaboration may help prevent such adverse events.