How Long Until It Works

• Onset of therapeutic actions may be sooner than with other SSRIs due to vilazodone’s actions at serotonin 1A receptors, with current data suggesting onset of efficacy as early as week 1, despite the fact that standard titration does not arrive at full therapeutic dose of 40 mg until the third week

• If it is not working within 6 or 8 weeks, it may require a dosage increase (off label) or it may not work at all

• May continue to work for many years to prevent relapse of symptoms

If It Works

• The goal of treatment is complete remission of current symptoms as well as prevention of future relapses

• Treatment most often reduces or even eliminates symptoms, but not a cure since symptoms can recur after medicine stopped

• Continue treatment until all symptoms are gone (remission) or significantly reduced

• Once symptoms gone, continue treating for 1 year for the first episode of depression

• For second and subsequent episodes of depression, treatment may need to be indefinite

• Use in anxiety disorders may also need to be indefinite

If It Doesn’t Work

• Many patients have only a partial response where some symptoms are improved but others persist (especially insomnia, fatigue, and problems concentrating)

• Other patients may be nonresponders, sometimes called treatment-resistant or treatment-refractory

• Some patients who have an initial response may relapse even though they continue treatment, sometimes called “poop-out”

• Consider increasing dose to 50–80 mg/day “off label” over several weeks if tolerated

• Consider switching to another agent or adding an appropriate augmenting agent

• Consider psychotherapy

• Consider evaluation for another diagnosis or for a comorbid condition (e.g., medical illness, substance abuse, etc.)

• Some patients may experience apparent lack of consistent efficacy due to activation of latent or underlying bipolar disorder, and require antidepressant discontinuation and switch to a mood stabilizer

Best Augmenting Combos for Partial Response or Treatment Resistance

• Trazodone, especially for insomnia

• Bupropion, mirtazapine, reboxetine, or atomoxetine (use combinations of antidepressants with caution as this may activate bipolar disorder and suicidal ideation)

• Modafinil, especially for fatigue, sleepiness, and lack of concentration

• Mood stabilizers or atypical antipsychotics for bipolar depression, psychotic depression, treatment-resistant depression, or treatment-resistant anxiety disorders

• Benzodiazepines

• If all else fails for anxiety disorders, consider gabapentin, pregabalin, or tiagabine

• Hypnotics for insomnia

• Classically, lithium, buspirone, or thyroid hormone

Tests

• None for healthy individuals

Vilazodone: side effects How Drug Causes Side Effects

• Theoretically due to increases in serotonin concentrations at serotonin receptors in parts of the brain and body other than those that cause therapeutic actions (e.g., unwanted actions of serotonin in sleep centers causing insomnia, unwanted actions of serotonin in the gut causing diarrhea, etc.)

• Increasing serotonin can cause diminished dopamine release and might contribute to emotional flattening, cognitive slowing, and apathy in some patients

• Most side effects are immediate but often go away with time, in contrast to most therapeutic effects, which are delayed and are enhanced over time