Buspar (Buspirone) Dosing Schedule
Buspar should be administered at 9am and 9pm (every 12 hours) rather than 9am and 5pm, as the drug's short elimination half-life of approximately 2.5 hours necessitates consistent twice-daily dosing intervals to maintain therapeutic plasma levels throughout the day. 1, 2
Pharmacokinetic Rationale for 12-Hour Dosing Intervals
- Buspirone has an elimination half-life of only 2.1-2.5 hours after oral administration, meaning the drug is rapidly cleared from the body 3, 2
- The active metabolite 1-pyrimidinylpiperazine (1-PP) has a longer half-life of 6.1 hours, but this still requires consistent dosing intervals 3, 2
- After a single 20mg dose, peak plasma concentrations occur within 1 hour, followed by rapid decline 2
- No drug accumulation occurs with multiple-dose administration, confirming the need for regular dosing intervals 2
Standard Dosing Regimen
- The typical therapeutic dose is 15-30 mg/day divided into 2-3 doses 4, 5
- When used as an anti-shivering agent during targeted temperature management, buspirone is administered at 30mg every 8 hours 1
- For anxiety disorders, the standard approach is twice-daily dosing to maintain consistent anxiolytic effects 4, 6
Clinical Considerations for Timing
- Unlike bupropion (which has activating properties requiring morning and early afternoon dosing to avoid insomnia), buspirone causes minimal sedation and does not require specific timing to prevent sleep disturbances 7, 4
- The 9am and 9pm schedule provides optimal 12-hour intervals that align with most patients' wake-sleep cycles while maintaining therapeutic drug levels 2
- A 9am and 5pm schedule (8-hour interval followed by 16-hour gap overnight) would result in subtherapeutic levels during the extended overnight period 2
Important Caveats
- Buspirone requires 1-2 weeks to achieve full anxiolytic effect, so patient compliance and motivation are essential during the initial treatment period 4, 5
- Food increases buspirone bioavailability 2-fold, so consistent administration with or without food is recommended to maintain stable plasma levels 2
- Patients with hepatic impairment require dose reduction, as the half-life doubles and plasma concentrations increase 15-fold in this population 2