Buspar
Buspar
Generic Name
Buspar
Mechanism
- Selective partial agonist at presynaptic α2‑adrenergic and postsynaptic 5‑HT1A serotonergic receptors, producing anxiolytic effects.
- Modulates dopaminergic tone centrally, reducing catecholamine overactivity linked to anxiety.
- Lacks significant affinity for GABA‑A, benzodiazepine, or adrenergic β‑receptors, which accounts for minimal sedative‑hypnotic profile.
Pharmacokinetics
- Absorption: 50–60 % oral bioavailability; peak plasma levels in 1–4 h.
- Distribution: High systemic protein binding (~65 %); crosses blood‑brain barrier.
- Metabolism: Hepatic CYP3A4‑mediated to active metabolites (buspirone‑N‑oxide, β‑hydroxybuspirone).
- Elimination: Half‑life ≈ 2.5 h (active metabolites 4–5 h); renal excretion (~20 % unchanged).
> *Clinical tip:* CYP3A4 inhibitors (e.g., ketoconazole) raise plasma buspirone; consider dose adjustments.
Indications
- Generalized Anxiety Disorder (GAD) – first‑line therapy for moderate‑to‑severe cases.
- Anxiety disorders with comorbid mood disorders – safe adjunct to antidepressants.
- Pre‑operative anxiety – used in elective settings to reduce acute peri‑operative stress.
Buspar is not indicated for panic attacks, social anxiety without GAD, or short‑term situational anxiety.
Contraindications
| Category | Key Points |
| Contraindications | Known hypersensitivity to buspirone or tolbutamide; severe hepatic impairment (eGFR *Rule of thumb:* Use cautiously in patients on CYP3A4 inhibitors and those with impaired liver function.
Dosing
| Form | Typical Schedule | Titration Notes |
| PO Tablets (12.5 mg) | 2–3 mg TID → 30–45 mg/d | Begin 2.5 mg QID → titrate 5 mg every 5–7 days to 3–4 mg TID; hold if GI upset. |
| PO Oral Solution (3 mg/mL) | 2–3 mL 3× daily | Helpful for pediatric/geriatric patients with swallowing difficulties. |
| Intravenous | No established IV formulation | Not commonly used. |
• Maximum: 90 mg/day (12.5 mg PO TID + 30 mg PO QID), rarely needed.
• Onset: 1–2 weeks for anxiolytic effect; therapeutic response may take up to 12 weeks.
Adverse Effects
Common (≥ 5 %)
• Nausea, headache, dizziness, insomnia, palpitations, abdominal pain.
Serious (≤ 1 %)
• Seizures, syncope, severe hypotension, angioedema, QT prolongation (rare).
> *Monitoring tip:* Watch for dizziness and orthostatic hypotension in the first weeks of therapy.
Monitoring
- Baseline: CBC, LFTs, serum electrolytes, ECG if cardiac risk.
- During treatment:
- Assess anxiety scale (e.g., GAD‑7) every 2–4 weeks.
- Monitor weight, sleep quality, medication adherence.
- Optional: QTc interval if patient on other QT‑prolonging drugs.
Clinical Pearls
1. Avoid abrupt withdrawal – taper buspirone over 2–3 weeks to prevent rebound anxiety.
2. No rapid anxiolysis – patient should be counseled that effect builds over weeks; not suitable for acute panic episodes.
3. Combination therapy – synergistic with SSRIs; buspirone may counteract SSRI‑induced anxiety.
4. Older adults – start at the lowest dose (2.5 mg QID) because of reduced hepatic clearance.
5. Pediatric use – dosing based on weight (≤ 3 mg/m² QID) with close monitoring for growth and developmental effects.
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• *For more detailed clinical guidance, consult the latest FDA labeling and peer‑reviewed pharmacology reviews.*