buspirone
Brand: Buspar
Prototype Drug
Drug Class: non-benzodiazepine anxiolytic
Drug Family: anxiolytic
Subclass: azapirone serotonin partial agonist
Organ Systems: cns
Mechanism of Action
Partial agonist at 5-HT1A receptors (both pre- and post-synaptic); presynaptic 5-HT1A autoreceptor activation reduces serotonin release initially, while postsynaptic effects develop over 2–4 weeks (explaining delayed onset). Also acts as a presynaptic D2 dopamine receptor agonist.
5-HT1A serotonin receptor (partial agonist)D2 dopamine receptor (presynaptic)
Indications
- generalized anxiety disorder (GAD)
Contraindications
- concurrent MAOI use (serotonin syndrome risk)
- severe hepatic or renal impairment
Adverse Effects
Common
- dizziness
- headache
- nausea
- nervousness
- paresthesias
Serious
- serotonin syndrome (with MAOIs or other serotonergic drugs)
- dizziness and falls (in elderly)
Pharmacokinetics (ADME)
| Absorption | oral; bioavailability ~4% (extensive first-pass); food increases bioavailability |
| Distribution | 86–95% protein bound |
| Metabolism | hepatic via CYP3A4 to active metabolite (1-PP — contributes to efficacy and alpha2 antagonism) |
| Excretion | renal (29–63%) and fecal (18–38%) |
| Half-life | 2–3 hours |
| Onset | 2–4 weeks (significant delay) |
| Peak | 0.7–1.5 hours |
| Duration | ongoing with daily dosing |
| Protein Binding | 86–95% |
| Vd | 5.3 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| MAOIs | risk of serotonin syndrome; contraindicated | contraindicated |
| CYP3A4 inhibitors (diltiazem, verapamil) | increase buspirone levels significantly; reduce dose | major |
| rifampin | CYP3A4 induction reduces buspirone levels by 90% | major |
Nursing Considerations
- Counsel patients that buspirone requires 2–4 weeks for full anxiolytic effect; unlike benzodiazepines, immediate relief is NOT expected.
- Patients switched from benzodiazepines to buspirone must be tapered off benzodiazepines gradually; buspirone does NOT cross-react with benzodiazepine receptors.
- Take consistently with or without food (food increases bioavailability 2-fold; consistency reduces variability).
- Buspirone does not cause sedation, respiratory depression, or dependence — major advantages over benzodiazepines for long-term anxiety management.
Clinical Pearls
- Buspirone's most important clinical characteristic is that it has NO cross-tolerance with benzodiazepines — patients switching from benzodiazepines to buspirone will not be protected from benzodiazepine withdrawal and will not experience immediate anxiolysis.
- Unlike SSRIs and SNRIs, buspirone's efficacy appears limited to GAD; it is not effective for panic disorder, social anxiety, PTSD, or OCD — a limitation that restricts its use to a narrower anxiety profile.
Safety Profile
Pregnancy avoid
Lactation insufficient-data
Renal Adjustment Required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.