What is the starting dose of Buspar (buspirone) for an adult patient with anxiety?

Starting Dose of Buspar for Adult Anxiety

Start buspirone at 5 mg twice daily (BID) for most adult patients with generalized anxiety disorder, then titrate upward by 5 mg every 2-3 days to reach the therapeutic range of 15-30 mg/day. 1, 2

Initial Dosing Strategy

• The standard starting dose is 5 mg twice daily (10 mg/day total), which is the most commonly recommended approach by the American Academy of Family Physicians 1, 2
• An alternative starting approach of 7.5 mg twice daily exists, though the lower 5 mg BID dose is preferred to minimize initial side effects 1
• Increase the dose gradually by 5 mg/day increments every 2-3 days based on patient response and tolerability 1, 2

Target Therapeutic Dosing

• The target therapeutic dose range is 15-30 mg/day in divided doses, which is where most patients achieve optimal anxiety control 1, 2, 3
• The maximum recommended dose is 60 mg/day (20 mg three times daily), though this is rarely needed 1, 2
• Most patients in long-term studies were successfully managed on 15-30 mg/day 3

Special Population Adjustments

• Elderly or debilitated patients should start at lower doses of 2.5-5 mg twice daily and titrate more gradually, as this population demonstrates increased sensitivity to medication effects 1
• The American Geriatrics Society specifically recommends buspirone for elderly patients due to its lack of sedation, cognitive impairment, and fall risk compared to benzodiazepines, with a mean effective dose of 18 mg/day (range 5-30 mg/day) 2
• Patients with hepatic impairment require dose reduction, as buspirone concentrations can be 15-fold higher in this population 4
• Patients with renal impairment may need dose adjustments, as concentrations can be 2-fold higher after a single dose 4

Critical Timing Expectations

• Buspirone requires 2-4 weeks for full therapeutic effect, making it inappropriate for acute anxiety requiring immediate relief 2
• Some studies note a "lagtime" of 1-2 weeks to onset of anxiolytic effect, so patient motivation and compliance counseling is essential 5
• Assess treatment response at 2-4 weeks minimum, not earlier, to ensure adequate treatment duration before determining efficacy 2
• Full therapeutic trials may require 4-8 weeks before making definitive efficacy determinations 1

Common Prescribing Pitfalls to Avoid

• Do not start at too high a dose, as this increases side effects without providing faster benefit 2
• Do not discontinue prematurely before the 2-4 week therapeutic window, as this is the most common reason for treatment failure 2
• Schedule the second daily dose earlier in the day rather than late evening to minimize insomnia risk 2
• Buspirone is only useful for mild-to-moderate anxiety and is not effective for severe agitation or acute panic 2

Important Drug Interactions Affecting Dosing

• Coadministration with verapamil, diltiazem, erythromycin, or itraconazole substantially increases buspirone plasma concentrations, requiring dose reduction 4
• Rifampin decreases buspirone concentrations almost 10-fold, potentially requiring dose increases 4
• Cimetidine and alprazolam have negligible effects on buspirone pharmacokinetics 4

Administration Considerations

• Food increases buspirone absorption 2-fold (both Cmax and AUC), so consistent administration timing relative to meals is important for stable dosing 4
• The drug has a short elimination half-life of approximately 2.5 hours, supporting the divided dosing schedule 4, 6
• When discontinuing after prolonged use (>6 months), abrupt cessation does not produce withdrawal syndrome or unusual events 3