Quetiapine (Seroquel)

Quetiapine (Tradename: Seroquel) is an atypical antipsychotic.

  • Tmax = 1-3 hours
  • Half-life = 6-12 hours

Quetiapine is an antagonist at serotonin 5-HT1A and 5HT2, dopamine D1 and D2, histamine H1, and adrenergic alpha 1 and alpha 2 receptors.

Quetiapine has two formulations with different pharmacokinetic properties: immediate release (IR) and extended release (XR)

Quetiapine Immediate Release (IR) vs. Extended Release (XR)

Generic name Quetiapine Immediate Release (IR) Quetiapine Extended Release (XR)
Tradename Seroquel IR Seroquel XR
Dosage Strengths 25 mg, 50 mg, 100 mg, 150 mg, 200 mg, 300 mg, 400 mg tablets 50 mg, 150mg, 200mg, 300mg, 400mg tablets
Half-life Shorter Longer
Dosing BID dosing Once daily dosing
Starting Dose (Bipolar Mania) 50 mg BID (increase by 100-200 mg/day) 300 mg PO daily (can increase by 300 mg/day)
Target Dose (Bipolar Mania) 400-800 mg PO daily[1] 400-800 mg PO daily
Advantages May be more beneficial in acute mania and psychosis due to more sedating features Faster dose titration and less sedating
Disadvantages More sedating Lower side effect profile

Sedation and weight gain could be dose limiting factors. In his case, if one were to use this approach, one should start at a low dose of 25 mg po qhs and increase as indicated and tolerated in 25 mg increments every 2-3 weeks. Maximum dose can go up to 1200mg.

Increases by 100-200mg/day as rapid titration in an inpatient is possible.[3]

There does not appear to be a bleeding risk, however, there are other possible haematological side effects. i.e., leucopenia and neutropenia. CBC should be monitored. QTc prolongation is also possible.