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Buspirone
Buspirone hydrochloride tablets are indicated for managing anxiety disorders, with efficacy demonstrated in controlled trials of outpatients whose diagnosis roughly corresponded to generalized anxiety disorder1. It lacks the prominent sedation associated with more typical anxiolytics1. In human and animal studies, there is no evidence that buspirone causes physical or psychological dependence1. It is also described as lacking prominent sedative; it also does not exert anticonvulsant or muscle-relaxant effects1. Commonly observed adverse events reported more often than with placebo include nausea, headache, and dizziness1; rare voluntary postmarketing reports have included movement-related events, with no established causal relationship to buspirone treatment1. Potentially life-threatening serotonin syndrome has been reported with buspirone alone, particularly with concomitant use of other serotonergic drugs; seizures may be a symptom of this syndrome1.
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
Duration
Subjective Effects
Pharmacology
Pharmacodynamics
Buspirone primarily modulates serotonin signaling through 5-HT1A receptors, acting as a full agonist at presynaptic autoreceptors in the dorsal raphe and a partial agonist at postsynaptic receptors in forebrain regions.2 Presynaptic activation initially reduces serotonergic neuron firing and serotonin release, while subsequent autoreceptor desensitization may increase serotonergic activity over time.2 Buspirone also has weak antagonistic activity at dopamine D2, D3, and D4 receptors and lower-affinity antagonistic activity at several serotonin receptors, including 5-HT2A, 5-HT2B, 5-HT2C, 5-HT6, and 5-HT7. It does not affect GABA binding in vitro or in vivo when tested in preclinical models1.
Pharmacokinetics
Buspirone is rapidly absorbed orally1 but undergoes extensive first-pass metabolism, with very low plasma concentrations of unchanged buspirone that vary between subjects after oral administration1. Food decreases absorption while also reducing first-pass metabolism, resulting in increased bioavailability, Cmax, and AUC. Peak plasma concentrations have been observed 40 to 90 minutes after single oral doses of 20 mg1. Buspirone is metabolized primarily through oxidation, shown in vitro to be mediated by CYP3A41. About 29% to 63% of a dose is excreted in urine within 24 hours, mainly as metabolites, and 18% to 38% is eliminated in feces.1 The elimination half-life of unchanged buspirone is about 2 to 3 hours.1
Interactions
An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.
Tolerance
Harm Potential
Toxicity
Buspirone appears relatively benign in single-drug overdose, although definitive data are unavailable. Deliberate doses of 250–300 mg caused drowsiness in about half of individuals, while doses up to 2,400 mg/day in clinical trials were associated with akathisia, tremor, and muscle rigidity.
LD50 Data
| Species | Route | Value |
|---|---|---|
| rat | oral | 196 mg/kg |
| mouse | oral | 655 mg/kg |
| dog | oral | 586 mg/kg |
| monkey | oral | 356 mg/kg |
Seizure Risk
Seizures are reported as a serious possible side effect of buspirone.4
History & Culture
Buspirone was first synthesized by a team at Mead Johnson in 1968. It was initially developed as a dopamine D2–acting antipsychotic but proved ineffective for psychosis before being redirected for use as an anxiolytic.5 Bristol-Myers Squibb received U.S. Food and Drug…
Legality
By Country
United StatesPrescription only
CanadaPrescription onlyReferences
Citations
Further Reading
Article Status
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