What are the considerations when prescribing Buspar (buspirone)?

Key Considerations When Prescribing Buspirone (BuSpar)

Buspirone is most effective for generalized anxiety disorder but requires 2-4 weeks to achieve therapeutic effect, with an initial dosage of 5 mg twice daily, gradually titrated to a maximum of 60 mg daily. 1

Indications and Mechanism of Action

• Primarily indicated for generalized anxiety disorder (GAD), not effective for other anxiety disorders like panic disorder 2
• Acts as a serotonin 5-HT1A receptor agonist with some affinity for dopamine D2 receptors 3
• Lacks the sedative, muscle relaxant, and anticonvulsant properties of benzodiazepines 3
• May be used as an adjunct for depression treatment or for managing sexual side effects of other medications 2

Dosing Considerations

• Initial dose: 5 mg twice daily 1
• Titration: Increase by 5 mg every 2-3 days as needed and tolerated
• Typical therapeutic dose: 20-30 mg daily in divided doses
• Maximum dose: 60 mg daily (20 mg three times daily) 1
• Onset of action: 2-4 weeks for full therapeutic effect (unlike benzodiazepines which work immediately) 1
• For elderly patients: Start with lower doses (e.g., 5 mg once or twice daily)

Pharmacokinetics

• Rapid absorption with peak plasma concentration under 1 hour 4
• Low bioavailability (approximately 4%) due to extensive first-pass metabolism 4
• Short half-life of approximately 2.5 hours 4
• Metabolized to active metabolite 1-pyrimidinylpiperazine (1-PP) 3
• Food increases plasma concentration approximately 2-fold 4

Advantages Over Benzodiazepines

• No risk of physical dependence or withdrawal symptoms 3
• No abuse potential 3
• Does not impair psychomotor performance 3
• No potentiation of alcohol effects 3
• No development of tolerance to anxiolytic effects 3

Adverse Effects

Common (>1%)

• Dizziness (12% vs 3% with placebo) 5
• Headache (6% vs 3% with placebo) 5
• Nausea (8% vs 5% with placebo) 5
• Nervousness (5% vs 1% with placebo) 5
• Lightheadedness (3%) 5
• Drowsiness (10% vs 9% with placebo) 5
• Dry mouth (3% vs 4% with placebo) 5

Less Common

• Insomnia, decreased concentration, excitement 5
• Blurred vision, gastrointestinal disturbances 5
• Paresthesia, incoordination, tremor 5

Contraindications and Precautions

• Absolute contraindications:

  • Hypersensitivity to buspirone 5
  • Concomitant use with MAOIs or within 14 days of stopping MAOIs 5
  • Starting buspirone in patients on linezolid or methylene blue 5

• Use with caution in:

  • Hepatic impairment: Plasma concentrations can be 15-fold higher; reduce dose by 50% 4
  • Renal impairment: 2-fold increase in plasma concentration; reduce dose 4
  • Elderly patients: Start with lower doses

Drug Interactions

• Significant interactions:

  • MAOIs: Contraindicated due to risk of serotonin syndrome and hypertension 5
  • CYP3A4 inhibitors (verapamil, diltiazem, erythromycin, itraconazole): Substantially increase buspirone levels 4
  • CYP3A4 inducers (rifampin): Can decrease buspirone levels by up to 10-fold 4
  • Other serotonergic drugs (SSRIs, SNRIs, triptans): Increased risk of serotonin syndrome 5

• Monitor for serotonin syndrome symptoms:

  • Mental status changes (agitation, hallucinations, delirium)
  • Autonomic instability (tachycardia, labile blood pressure, hyperthermia)
  • Neuromuscular changes (tremor, rigidity, hyperreflexia)
  • Gastrointestinal symptoms (nausea, vomiting, diarrhea) 5

Patient Education Points

• Emphasize that therapeutic effect takes 2-4 weeks to develop
• Explain the importance of consistent dosing
• Advise that it does not cause sedation or impair functioning like benzodiazepines
• Inform about potential side effects and when to report them
• Warn about potential drug interactions, especially with over-the-counter medications
• Explain that it should not be abruptly discontinued after long-term use

Monitoring Parameters

• Assess anxiety symptoms at baseline and follow-up visits
• Monitor for adverse effects, particularly dizziness and headache
• Evaluate for signs of serotonin syndrome if combined with other serotonergic medications
• No specific laboratory monitoring required

Clinical Pearls

• Unlike benzodiazepines, buspirone is not effective for "as needed" anxiety management due to delayed onset
• Patients previously treated with benzodiazepines may perceive buspirone as less effective due to lack of immediate sedative effects
• Taking with food increases absorption but may also increase side effects
• Buspirone may be particularly useful for elderly patients or those with substance use concerns due to lack of abuse potential