Viibryd - Drug Monograph

Introduction

Viibryd (vilazodone hydrochloride) is an antidepressant medication approved by the U.S. Food and Drug Administration (FDA) for the treatment of major depressive disorder (MDD) in adults. It represents a unique pharmacological class as both a selective serotonin reuptake inhibitor (SSRI) and a partial agonist at serotonin 5-HT1A receptors. This dual mechanism distinguishes it from other antidepressants and may offer particular benefits in clinical practice.

Mechanism of Action

Viibryd exerts its therapeutic effects through two primary mechanisms: 1. Serotonin Reuptake Inhibition: Potently inhibits the serotonin transporter (SERT), increasing synaptic serotonin concentrations 2. 5-HT1A Receptor Partial Agonism: Acts as a partial agonist at serotonin 5-HT1A receptors, which may contribute to its antidepressant and anxiolytic effects while potentially reducing side effects associated with pure SSRIs

This dual activity is thought to provide a more rapid onset of antidepressant action and potentially improved tolerability compared to conventional SSRIs.

Indications

• FDA-approved: Treatment of major depressive disorder (MDD) in adults
• Off-label uses: While not FDA-approved for these conditions, some clinical evidence supports use in:

- Generalized anxiety disorder - Panic disorder - Social anxiety disorder

Dosage and Administration

• Renal impairment: No dosage adjustment necessary for mild to moderate impairment; use caution in severe impairment
• Hepatic impairment: No dosage adjustment necessary for mild to moderate impairment; not recommended in severe impairment
• Elderly: No dosage adjustment necessary based on age alone
• Pediatric: Safety and effectiveness not established in children

Pharmacokinetics

Contraindications

• Concomitant use with monoamine oxidase inhibitors (MAOIs) or within 14 days of MAOI discontinuation
• Known hypersensitivity to vilazodone or any component of the formulation
• Concomitant use with pimozide

Warnings and Precautions

• Increased risk of suicidal thoughts and behaviors in children, adolescents, and young adults
• All patients should be monitored for clinical worsening and emergence of suicidal thoughts

• Serotonin syndrome: Risk especially when used with other serotonergic drugs
• Activation of mania/hypomania: Screen for bipolar disorder
• Discontinuation syndrome: Taper gradually when discontinuing
• Abnormal bleeding: Increased risk of bleeding events
• Angle-closure glaucoma
• Hyponatremia: Monitor sodium levels in elderly patients and those on diuretics
• QT prolongation: Use with caution in patients with risk factors for QT prolongation

Drug Interactions

• MAOIs: Risk of serotonin syndrome (contraindicated)
• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): Increase vilazodone levels; reduce Viibryd dose to 20 mg
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): Decrease vilazodone levels; consider dose adjustment
• Serotonergic drugs (e.g., tramadol, triptans, other antidepressants): Increased serotonin syndrome risk
• Anticoagulants/antiplatelets (e.g., warfarin, NSAIDs): Increased bleeding risk
• Drugs that prolong QT interval: Additive effects possible

Adverse Effects

• Diarrhea (28% vs 9% placebo)
• Nausea (23% vs 5% placebo)
• Insomnia (6% vs 2% placebo)
• Vomiting (5% vs 1% placebo)

• Suicidal thoughts and behaviors
• Serotonin syndrome
• Mania/hypomania
• Seizures
• Abnormal bleeding
• Angle-closure glaucoma
• Hyponatremia

Monitoring Parameters

• Mental status: Monitor for emergence of suicidal thoughts, especially during initiation and dose changes
• Clinical response: Assess depressive symptoms using standardized scales (e.g., PHQ-9)
• Adverse effects: Monitor for GI symptoms, insomnia, activation symptoms
• Laboratory: Consider sodium monitoring in elderly patients and those on diuretics
• Drug interactions: Review medication regimen regularly
• Discontinuation symptoms: Monitor during taper and after discontinuation

Patient Education

• Take medication exactly as prescribed, with food
• Do not abruptly discontinue without medical supervision
• Be aware of potential side effects and report concerning symptoms
• Inform all healthcare providers about Viibryd use
• Avoid alcohol during treatment
• Use caution when driving or operating machinery until effects are known
• Report any worsening depression or suicidal thoughts immediately
• Use effective contraception if sexually active and of reproductive potential
• Allow several weeks for full therapeutic effect

References

1. FDA Prescribing Information: Viibryd (vilazodone hydrochloride) tablets. Revised 2021. 2. Khan A, Cutler AJ, Kajdasz DK, et al. A randomized, double-blind, placebo-controlled, 8-week study of vilazodone, a serotonergic agent for the treatment of major depressive disorder. J Clin Psychiatry. 2011;72(4):441-447. 3. Rickels K, Athanasiou M, Robinson DS, et al. Evidence for efficacy and tolerability of vilazodone in the treatment of major depressive disorder: a randomized, double-blind, placebo-controlled trial. J Clin Psychiatry. 2009;70(3):326-333. 4. Stahl SM. Mechanism of action of vilazodone: a novel antidepressant for the treatment of major depressive disorder. J Clin Psychiatry. 2011;72(9):1166-1173. 5. Citrome L. Vilazodone for major depressive disorder: a systematic review of the efficacy and safety profile for this newly approved antidepressant. Int J Clin Pract. 2012;66(4):356-368. 6. American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder. 3rd ed. 2010.