BUSPAR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BUSPAR (BUSPAR).
Partial agonist at serotonin 5-HT1A receptors, leading to reduced serotonergic activity; also has antagonist activity at D2 and 5-HT2 receptors.
| Metabolism | Hepatic, primarily via CYP3A4 |
| Excretion | Renal: 29–63% (primarily as metabolites, <1% unchanged); Fecal: 34–38%; Biliary: minimal |
| Half-life | 2–3 hours (terminal); clinical context: requires multiple daily dosing; steady-state achieved in ~2 days |
| Protein binding | 86–95% bound (primarily to albumin and alpha-1-acid glycoprotein) |
| Volume of Distribution | 5–6 L/kg (suggests extensive tissue distribution, not limited to plasma) |
| Bioavailability | Oral: ~90% (but subject to extensive first-pass metabolism; absolute bioavailability ~4% due to high presystemic clearance) |
| Onset of Action | Oral: 1–2 weeks for initial anxiolytic effect; full effect at 4–6 weeks |
| Duration of Action | 3–6 hours (due to short half-life); clinical note: immediate-release formulations require 2–3 times daily dosing |
Initial: 7.5 mg orally twice daily; may increase by 5 mg/day every 2-3 days. Usual: 20-30 mg/day in divided doses; max 60 mg/day.
| Dosage form | TABLET |
| Renal impairment | No specific GFR-based adjustments recommended; use with caution in severe renal impairment (CrCl < 30 mL/min) due to limited data. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated. |
| Pediatric use | Not FDA-approved for pediatric use. Limited data: initial 5 mg/day, titrate up to 0.6 mg/kg/day, maximum 60 mg/day. |
| Geriatric use | Initial: 5 mg twice daily; titrate slowly due to increased sensitivity and reduced clearance. Maximum 30 mg/day recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BUSPAR (BUSPAR).
| Breastfeeding | Buspirone is excreted into human breast milk with an estimated infant dose of 0.1-0.5% of maternal weight-adjusted dose. M/P ratio is approximately 0.5-0.9 based on limited data. No adverse effects reported in breastfed infants. Caution recommended due to limited safety data. |
| Teratogenic Risk | Buspirone (BUSPAR) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects, but adequate and well-controlled studies in pregnant women are lacking. First trimester: No increased risk of major congenital malformations reported in limited human data. Second and third trimesters: No known specific fetal risks; however, potential for neonatal adverse effects (e.g., poor adaptation) if used near term, though data are insufficient. Use only if clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to buspirone","Concurrent use of MAOIs (including linezolid and IV methylene blue)"]
| Precautions | ["Concomitant use with MAOIs may cause serotonin syndrome","Risk of CNS depression with alcohol or other depressants","May cause dizziness, drowsiness","Tapering not required but abrupt discontinuation may cause withdrawal symptoms","Not effective for PRN use due to delayed onset"] |
| Food/Dietary | Grapefruit juice significantly increases buspirone serum concentrations; avoid concurrent consumption. High-fat meals may decrease absorption but no specific restriction; take consistently with or without food. |
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| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor maternal blood pressure and heart rate due to buspirone's potential cardiovascular effects. Assess for signs of serotonin syndrome if co-administered with other serotonergic drugs. Fetal monitoring not routinely indicated. |
| Fertility Effects | No known significant effects on fertility in humans. Animal studies at high doses showed some effects on estrous cycles and spermatogenesis; clinical relevance unknown. Limited data suggest no major impact on reproductive function. |
| Clinical Pearls |
| Buspirone has a slow onset of action (2-4 weeks); not effective for acute anxiety or panic attacks. No significant abuse potential or sedation, making it suitable for patients with substance abuse history or those requiring alertness. Avoid concurrent use with MAOIs due to risk of serotonin syndrome. Dose adjustment needed in hepatic impairment; no adjustment in renal impairment. |
| Patient Advice | Take buspirone consistently at the same times each day, with or without food. · Do not expect immediate relief; it may take 2-4 weeks to feel full effects. · Avoid grapefruit juice as it can increase buspirone levels and side effects. · Do not consume alcohol while taking buspirone. · Do not stop abruptly; follow doctor's instructions for discontinuation to avoid withdrawal symptoms such as nervousness or insomnia. |