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Quetiapine (Seroquel)

Antipsychoticprescriptionoral · predicted

Atypical antipsychotic with dose-dependent pharmacology: at low doses (25-100 mg) primarily an H1/alpha-1 antagonist (sedation/sleep), at moderate doses (150-300 mg) significant 5-HT2A antagonism and norepinephrine reuptake inhibition via norquetiapine (antidepressant), and at higher doses (400-800 mg) D2 antagonism (antipsychotic). Active metabolite norquetiapine has potent NET inhibition. Used for schizophrenia, bipolar disorder, and adjunctive depression treatment.

Projected serum levels — 100 mg, twice daily

Quetiapine (Seroquel)
Quetiapine (Seroquel) modeled serum levels, 100 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1
Quetiapine (Seroquel) modeled serum levels with a loading dose of 151 mg, then 100 mg twice daily The first dose is larger so levels approach steady state faster. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 100 mg twice daily (oral).

Loading schedule: 151 mg on day 1, then 100 mg twice daily — reaching therapeutic levels sooner.

Modeled steady state after ~1 days: peak ≈ 110 mg, trough ≈ 44.9 mg body load. Population-based estimate over 15 days for a 100 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Antipsychotic
Route modeled
Oral
Model confidence
predicted
Half-life
6 h
Common dose
100 mg
Suggested maximum
800 mg/day
Reference dose range
50–800 mg (single dose)
Suggested cadence
twice daily
Validated against
100 mg oral — Cmax 0.25 mg/L at 1.5 h

Documented interactions

  • contraindicated
    Clarithromycin (Biaxin) + Quetiapine (Seroquel) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~5.00x

  • contraindicated
    Diltiazem + Quetiapine (Seroquel) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~5.00x

  • contraindicated
    Efavirenz (Sustiva) + Quetiapine (Seroquel) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~0.14x

  • contraindicated
    Grapefruit (whole fruit) + Quetiapine (Seroquel) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~5.00x

  • contraindicated
    Grapefruit Juice + Quetiapine (Seroquel) CYP inhibition

    Grapefruit Juice mechanism_based of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~5.00x

  • contraindicated
    Paxlovid (Nirmatrelvir/Ritonavir) + Quetiapine (Seroquel) CYP inhibition

    Paxlovid (Nirmatrelvir/Ritonavir) mechanism_based of CYP3A4 predicted to change Quetiapine (Seroquel) AUC by ~5.00x

Serum checks 193 modeled interaction pairings for quetiapine (seroquel) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Quetiapine monotherapy for bipolar II depression: a double-blind, placebo-controlled study (EMBOLDEN II) McElroy SL et al. · Journal of Clinical Psychiatry, 2010 DOI

    Large RCT (740 patients) demonstrating quetiapine 300-600 mg/day monotherapy significantly improved bipolar depression versus placebo, with response rates of 57-58% versus 46%.

  2. A randomized, placebo-controlled trial of quetiapine augmentation for treatment-resistant major depressive disorder El-Khalili N et al. · Journal of Clinical Psychiatry, 2010 DOI

    Pivotal trial establishing quetiapine XR 150-300 mg/day as effective augmentation for treatment-resistant MDD, significantly reducing MADRS scores versus antidepressant monotherapy.

  3. Clinical pharmacokinetics of quetiapine and its active metabolite norquetiapine DeVane CL, Nemeroff CB · Clinical Pharmacokinetics, 2001 DOI

    Comprehensive PK review establishing quetiapine half-life of 6-7 hours, active metabolite norquetiapine with half-life of 12 hours, CYP3A4-dependent metabolism, and dose-proportional pharmacokinetics.

3 published studies referenced in the app, each with a plain-language summary.