ModerateCaution
Both quetiapine and melatonin have sedative properties, and their combination produces additive CNS depression. Quetiapine is particularly sedating among antipsychotics due to potent histamine H1 receptor antagonism. Adding melatonin may cause excessive drowsiness, impaired cognitive function, and motor coordination problems, especially in elderly patients. However, in some clinical contexts (e.g., managing sundowning in delirium), the combination may be therapeutically beneficial.
Recommendation: If using melatonin with quetiapine, start with the lowest melatonin dose (0.5-1 mg) and take both at bedtime. Avoid driving or operating machinery. Be especially cautious if elderly or taking other CNS depressants. Report excessive daytime drowsiness, confusion, or coordination problems to your prescriber.
DangerousContraindicated
St. John's Wort is a potent CYP3A4 inducer that can reduce quetiapine plasma concentrations by up to 80%, essentially rendering the medication ineffective. The FDA-approved labeling for quetiapine states that doses may need to be increased up to 5-fold when co-administered with strong CYP3A4 inducers. Loss of quetiapine efficacy can lead to psychiatric decompensation, psychotic relapse, or manic episodes with potentially dangerous consequences.
Recommendation: Do NOT take St. John's Wort with quetiapine. This combination is contraindicated due to the risk of complete loss of antipsychotic efficacy. If you are currently taking both, contact your prescriber immediately. Do not abruptly stop St. John's Wort as quetiapine levels will rise over 7-14 days.
ModerateCaution
Valerian root has GABAergic and sedative properties that can produce additive CNS depression when combined with quetiapine. The combination may cause excessive drowsiness, dizziness, confusion, impaired motor coordination, and difficulty concentrating. Elderly patients are at increased risk for falls and respiratory depression. The interaction is pharmacodynamic rather than pharmacokinetic.
Recommendation: Avoid combining valerian root with quetiapine unless approved by your prescriber. If using both, avoid hazardous activities requiring alertness. Start valerian at the lowest dose and monitor for excessive sedation. Elderly patients should be especially cautious. Report excessive drowsiness or confusion to your prescriber.
SeriousConflict
THC-dominant cannabis can conflict with quetiapine's use for psychosis or bipolar mood stabilization. Continued cannabis use after psychosis onset is associated with higher relapse risk and poorer antipsychotic outcomes, and quetiapine's sedating effects can compound cannabis-related impairment. This is especially concerning with high-potency THC, daily use, driving, or other sedatives.
Recommendation: Avoid THC-dominant cannabis while taking quetiapine for psychosis or bipolar disorder. Tell your prescriber if you continue cannabis so they can monitor symptoms, adherence, and oversedation. Do not rely on spacing the doses to make the combination safe.
SeriousCaution
Alcohol can markedly increase quetiapine-related sleepiness, dizziness, slowed reactions, and poor coordination. Quetiapine's antihistamine and alpha-1 blocking effects already make sedation and orthostatic hypotension common, and alcohol can push this into falls, blackouts, or unsafe driving. Risk is highest at night, after dose increases, or with other sedatives.
Recommendation: Avoid alcohol while taking quetiapine. If alcohol was used, do not drive, take extra sleep aids, or take more quetiapine than prescribed. Get urgent help for extreme drowsiness, slow breathing, fainting, or inability to wake.
NutriStack