| Indication | For the management of anxiety disorders or the short-term relief of the symptoms of anxiety, and also as an augmention of SSRI-treatment against depression. |
| Pharmacodynamics | Buspirone is used in the treatment of generalized anxiety where it has advantages over other antianxiety drugs because it does not cause sedation (drowsiness) and does not cause tolerance or physical dependence. Buspirone differs from typical benzodiazepine anxiolytics in that it does not exert anticonvulsant or muscle relaxant effects. It also lacks the prominent sedative effect that is associated with more typical anxiolytics. in vitro preclinical studies have shown that buspirone has a high affinity for serotonin (5-HT1A) receptors. Buspirone has no significant affinity for benzodiazepine receptors and does not affect GABA binding in vitro or in vivo when tested in preclinical models. Buspirone has moderate affinity for brain D2-dopamine receptors. Some studies do suggest that buspirone may have indirect effects on other neurotransmitter systems. |
| Mechanism of action | Buspirone binds to 5-HT type 1A serotonin receptors on presynaptic neurons in the dorsal raphe and on postsynaptic neurons in the hippocampus, thus inhibiting the firing rate of 5-HT-containing neurons in the dorsal raphe. Buspirone also binds at dopamine type 2 (DA2) receptors, blocking presynaptic dopamine receptors. Buspirone increases firing in the locus ceruleus, an area of brain where norepinephrine cell bodies are found in high concentration. The net result of buspirone actions is that serotonergic activity is suppressed while noradrenergic and dopaminergic cell firing is enhanced. |
| Absorption | Rapidly absorbed in man. Bioavailability is low and variable (approximately 5%) due to extensive first pass metabolism. |
| Volume of distribution | Not Available |
| Protein binding | 95% (approximately 70% bound to albumin, 30% bound to alpha 1 -acid glycoprotein) |
| Metabolism | Metabolized hepatically, primarily by oxidation by cytochrome P450 3A4 producing several hydroxylated derivatives and a pharmacologically active metabolite, 1-pyrimidinylpiperazine (1-PP) |
| Route of elimination | In a single-dose study using 14C-labeled buspirone, 29% to 63% of the dose was excreted in the urine within 24 hours, primarily as metabolites; fecal excretion accounted for 18% to 38% of the dose. |
| Half life | 2-3 hours (although the action of a single dose is much longer than the short halflife indicates). |
| Clearance | Not Available |
| Toxicity | Oral, rat LD50 = 136 mg/kg. Symptoms of overdose include dizziness, drowsiness, nausea or vomiting, severe stomach upset, and unusually small pupils. |