Suspected Serotonin Syndrome Following Addition of ADHD Medication

Case at a Glance

A 26-year-old female presented with acute onset of tremors, muscle rigidity, tachycardia, and hyperthermia after starting viloxazine (Qelbree) while on a complex psychiatric medication regimen including bupropion, venlafaxine, and aripiprazole.

Patient's Story

The patient was prescribed viloxazine for ADHD management by her psychiatrist as an addition to her existing psychiatric medications. Her current regimen included bupropion XL, venlafaxine (Effexor), aripiprazole (Abilify), and butalbital/acetaminophen/caffeine for migraine management. Within 48 hours of initiating viloxazine, she developed acute symptoms including tremors, muscle stiffness, tachycardia (heart rate 134 bpm at rest), fever, chills, and severe myalgia. The patient discontinued viloxazine independently and contacted poison control for guidance.

Initial Assessment

Patient presented with constellation of symptoms suggestive of serotonin syndrome: tremor, rigidity, tachycardia, hyperthermia, and myalgia. Symptoms developed acutely following addition of viloxazine to existing serotonergic medications. Poison control recommended emergency department evaluation due to concern for potentially life-threatening drug interaction.

The Diagnostic Journey

Clinical presentation was consistent with serotonin syndrome given the temporal relationship with medication addition and characteristic symptom complex. The combination of venlafaxine (SNRI) and viloxazine (norepinephrine reuptake inhibitor with some serotonergic activity) likely precipitated the syndrome. Differential diagnosis included neuroleptic malignant syndrome, anticholinergic toxicity, and infectious etiology.

Final Diagnosis

Suspected serotonin syndrome secondary to drug-drug interaction between venlafaxine and newly initiated viloxazine

Treatment Plan

Immediate discontinuation of viloxazine (already completed by patient). Emergency department evaluation as recommended by poison control to assess severity and provide supportive care. Consideration of serotonin antagonists if symptoms persist or worsen. Gradual resumption of baseline psychiatric medications under medical supervision to avoid withdrawal complications.

Outcome and Follow-up

Patient reported improvement in tremors and tachycardia following viloxazine discontinuation, though constitutional symptoms persisted initially. Emergency department evaluation was recommended for comprehensive assessment and monitoring. Follow-up with psychiatrist planned for medication regimen adjustment and alternative ADHD treatment options.