Quetiapine Immediate-Release Can Be Dosed BID for Methamphetamine-Induced Psychosis
Yes, you can divide the total daily dose of immediate-release quetiapine into two equal doses (BID) for methamphetamine-induced psychosis, as this is the standard FDA-approved dosing schedule for schizophrenia and psychotic disorders. 1
Standard BID Dosing Schedule
The FDA label explicitly recommends BID dosing for immediate-release quetiapine in schizophrenia:
- Day 1: 25 mg twice daily (total 50 mg/day) 1
- Day 2: Increase to 50 mg twice daily (total 100 mg/day) 1
- Day 3: Increase to 100 mg twice daily (total 200 mg/day) 1
- Day 4: Increase to 150 mg twice daily (total 300-400 mg/day target) 1
The recommended therapeutic dose range is 150-750 mg/day, divided into 2-3 doses daily. 1
Why BID Dosing Is Preferred for Immediate-Release
Immediate-release quetiapine has a relatively short half-life, making twice-daily or three-times-daily dosing pharmacologically appropriate to maintain stable plasma levels throughout the day. 2 The standard titration schedule uses divided doses specifically to optimize tolerability during dose escalation and maintain therapeutic drug levels. 2
Clinical Evidence Supporting BID Dosing
Multiple clinical trials have demonstrated efficacy using BID dosing schedules:
- Fixed-dose studies showed that quetiapine 150-450 mg/day in divided doses was effective for acute schizophrenia, with no additional benefit at 600-750 mg/day. 3
- Comparative effectiveness studies used average daily doses of 254-525 mg/day in divided doses, showing equivalence to other antipsychotics. 3
- The BID schedule allows for individualized titration in increments of 25-50 mg twice daily at intervals of at least 2 days. 1
Important Dosing Considerations
Do not exceed 750 mg/day total dose as this is the FDA-approved maximum for immediate-release quetiapine. 1 While some case reports suggest higher doses, robust controlled data support the standard dosage range as appropriate for full therapeutic effect. 3
For methamphetamine-induced psychosis specifically, start conservatively and titrate based on symptom control and tolerability, as these patients may be particularly sensitive to sedation and other side effects. 1
Common Pitfalls to Avoid
- Avoid once-daily dosing with immediate-release formulation – this is only appropriate for the extended-release (XR) formulation, not the IR version. 4, 5
- Do not rush titration – the recommended 4-day titration schedule minimizes orthostatic hypotension and excessive sedation. 1
- Monitor for excessive sedation when using BID dosing, particularly in elderly or debilitated patients who should start at 50 mg/day total with slower titration. 1