- Quetiapine offers some benefits over other dopamine blocking medications. It has a much lower risk for EPS and a broad spectrum of effects. The main limitations are weight gain, sedation, and orthostasis. The extended-release formulation offers a once nightly dosing that can reduce daytime sedation.
- It has a number of FDA approved indications including use in schizophrenia, bipolar disorder, bipolar depression, and major depression as an adjunct
- It’s mechanism of action is blocking dopamine D2 receptors which targets positive symptoms of psychosis and serotonin 2A receptors which enhance dopamine release in certain regions of the brain reducing motor side effects and possibly improving cognitive side effects. It’s effects on depression and bipolar depression may be related to 5HT1A partial agonist activity, norepinephrine reuptake blockade, and 5HT2C and 5HT7 antagonist properties.
- Clinically quetiapine is often underdosed and stopped or switched before an adequate trial is completed. Higher doses generally achieve greater response for manic or psychotic symptoms.
- For schizophrenia start with 25 mg BID or 300 mg XR QHS. Target doses 400-800 mg/day
- For bipolar start with 50 mg BID or 300 XR QHS. With a target dose of 400-800 mg daily for mania and 300 mg/day for depression (studies indicate that 600 mg was not better for depression than 300 mg)
- For depression start at 50-100 mg/day in divided doses with a target of 150-300 mg/day (data indicates that 150 mg and 300 mg do equally well so either dose is appropriate depending on patient response)
- You can increase the dose 50-100 mg/day every 1-4 days to a target dose
- The max daily dose in adults is 800 mg/day, occasionally patients may require 800-1,200 mg/day for psychosis or mania
- Monitoring is similar to other dopamine blocking medications, specifically fasting blood glucose and lipid profile, BMI, blood pressure
- Side effects include sedation, hypotension, dry mouth, dizziness, constipation, weight gain and fatigue. Watch for orthostatic hypotension at high doses or with rapid titration. There is essentially no motor side effects or prolactin elevation.
- For XR formulations do not crush or chew them, if a patient has been off the medication for more than 1 week you want to restart as if initial therapy. Quetiapine has some abuse potential reported in the literature particularly in incarcerated populations
- In the initial studies with beagle dogs cataracts developed but human studies have not shown this association