Quetiapine (Seroquel)

Second generation antipsychotic (25-100mg: histamine antagonist; 150-300 mg: norepinephrine reuptake inhibitor and presynaptic receptor antagonist; Over 300mg: dopamine, serotonin, norepinephrine receptor antagonist (D2, 5-HT2) and metabolite is a norepinephrine reuptake inhibitor)

Dosing

BP depression (300 mg qhs, might raise 30% if on lamotrigine), unipolar depression (150-300 mg qhs), manix/mixed (400-800 mg qhs), schizophrenia (600-800 mg qhs), OCD (100-300 mg qhs), sleep (25-100 mg qhs, but only use for sleep if patient has another condition it is indicated in as risk is too high).

Prefer XR form if going over 300 mg or patient is elderly as this reduces risk of orthostasis (give XR 1 hr away from food and 12 hr before they plan to wake up because it takes a few hours to release, food causes it to release all at once).

INTERACTIONS: Metabolized by 3A4 into an active metabolite with SNRI qualities. Avoid with carbamazepine as it will speed its metabolism into an antidepressant). Lower 2x with nefazodone and grapefruit juice. May need to lower a little with non-pram SSRIs (fluoxetine, fluvoxamine, paroxetine, sertraline ≥ 150 mg/day).

Management

Consider starting it on a weekend if sedation could interfere with work. Like mirtazapine, nefazodone, zyprexa and trazodone, it induces sedative effects through 5HT2-antagonism. Interactions: Avoid with carbamazepine as it will speed its metabolism into norquetiapine, which is basically an antidepressant (would also need to raise by 3-5x if using with carbamazepine, but can’t truly adjust it because of this active metabolite).

TOLERABILITY: Weight gain, sedation, akathisia, EPS (dystonia, stiffness), anticholinergic.

RISKS: Tardive dyskinesia (25% over 10 years, higher in elderly), metabolic, prolactinemia (can lead to breast cancer, osteopenia, sexual dysfunction), orthostasis (falls), QTc prolongation, temperature imbalance in elderly, NMS (muscle rigidity, fever, tachycardia).

EMR Text