From the FDA Drug Label
The no-effect dose in female rats was 1 mg/kg, or 0.01 times the MRHD of 800 mg/day on mg/m2 body surface area. Quetiapine decreased mating and fertility in male Sprague-Dawley rats at oral doses of 50 and 150 mg/kg or approximately 1 and 3 times the maximum human dose (MRHD) of 800 mg/day on mg/m2 body surface area.
The maximum recommended human dose (MRHD) of quetiapine is 800 mg/day 1.
From the Research
The maximum recommended dose of quetiapine is 800 mg per day for schizophrenia and acute mania in bipolar disorder, 600 mg daily for bipolar depression, and 300 mg daily for adjunctive treatment of major depressive disorder. This dosing is based on the most recent and highest quality studies, including a study published in 2011 2, which evaluated the effect of quetiapine on corrected QT intervals. The study found that quetiapine 800 mg/day was comparable to paliperidone ER 12 mg/day and 18 mg/day in terms of its effect on the QTc interval. Another study published in 2008 3 examined the dose-response relationship of quetiapine in schizophrenia and found that dosages of 150-450 mg/day were more effective than placebo and no less effective than dosages of 600 or 750 mg/day.
Some key points to consider when prescribing quetiapine include:
- Starting doses should be much lower (25-50 mg) with gradual increases over days to weeks to reduce side effects like sedation, orthostatic hypotension, and metabolic changes.
- Patients should be monitored for adverse effects including metabolic changes, QT prolongation, and extrapyramidal symptoms.
- Quetiapine works primarily by blocking dopamine and serotonin receptors, with its efficacy balanced against potential side effects to determine appropriate dosing for each individual.
- Elderly patients and those with hepatic impairment typically require lower maximum doses, often 50% of standard dosing.
- The doses are usually divided and taken twice daily.
It's also important to note that the use of high-dose quetiapine (>800 mg/day) is not well supported by robust controlled data, as stated in the 2008 study 3. Therefore, the maximum recommended dose of 800 mg per day should not be exceeded.