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Buspirone chemical structure

IUPAC name
CAS number
ATC code


Chemical formula {{{chemical_formula}}}
Molecular weight 385.50314 g/mol
Bioavailability low and variable (approx. 5%), due to high first pass metabolism
Metabolism mainly hepatic, active metabolite 1-Pyrimidylpiperazin (1-PP)
Elimination half-life 2-3h
Excretion urine (29-63%) and feces (18-38%) in the form of metabolites
Pregnancy category B, only use when clearly needed
Legal status Rx-only, not a controlled substance
Routes of administration oral

Buspirone (brand-names Ansial, Ansiced, Anxiron, Axoren, Bespar, BuSpar, Buspimen, Buspinol, Buspisal, Narol, Spitomin, Sorbon) is an anxiolytic agent and a serotonin receptor agonist belonging to the azaspirodecanedione class of compounds. Its structure is unrelated to those of the benzodiazepines, but it has an efficacy comparable to diazepam in treating generalized anxiety disorder.[1][2]

It shows no potential for addiction compared to other drugs commonly prescribed for anxiety, especially benzodiazepine medications [How to reference and link to summary or text]. The development of tolerance has not been noticed. Cross-tolerance to benzodiazepines, barbiturates and alcohol does not exist. Furthermore, it is non-sedating.

It is thought to act by interfering with the function of the neurotransmitter serotonin in the brain, particularly by serving as a 5-HT1A presynaptic receptor partial agonist. Additionally, it acts as a mixed agonist/antagonist on postsynaptic dopamine receptors. GABA-mediated effects are lacking. Buspirone may also have indirect effects on other neurotransmitters in the brain.

The action of a single dose is much longer than the short halflife of 2-3 hours indicates. The bioavailability of buspirone is very low and variable due to extensive first pass metabolism. The drug is quickly resorbed. Taking the drug together with food may increase the bioavailability. The drug is highly (95%) plasma-bound. The active metabolite 1-PP is also a 5-HT1A partial agonist with anxiolytic properties, but weaker so than the mother-drug.

It is also useful as an augmenting agent, for the treatment of depression, when added to SSRIs.

The main disadvantage is that 1 to 3 weeks elapse before the anxiolytic activity becomes evident. Often patients have to be initially cotreated with a benzodiazepine for immediate anxiolysis. Generally, buspirone works less well than benzodiazepines. Therefore, benzodiazepines are often the first approach in immediately treating panic attacks and social phobias. It is also particularly difficult to treat patients pretreated with benzodiazepines knowing the immediate effects of these tranquilizers.

Bristol-Myers Squibb gained FDA approval for Buspirone in 1986. The drug went generic in 2001.




Rarely, side-effects have a dangerous nature or intensity. Some tend to disappear with continued therapy, or are less frequent if the initial dose is low and increased gradually (vertigo, agitation, insomnia).

There are no dyscognitive side-effects like those seen in benzodiazepines.

Other side-effects have been seen, but are not more frequent than those encountered with placebo. An unusual side effect reported by patients has been an enhanced sense of smell.

Drug abuse and dependence

Buspirone has no known potential for abuse, psychological and physical dependence[How to reference and link to summary or text]


  • Haloperidol : increased plasma-levels of haloperidol
  • Rifampicin : decreased plasma-levels of buspirone
  • MAO-Inhibitors : severe hypertensive crises are possible.
  • Alcohol : The sedative properties of alcohol are increased slightly.
  • Grapefruit, Grapefruit juice, Grapefruit extract : drastically increased plasma-levels of Buspirone [3]


Initially, 10-15mg in 2-3 single doses per day. The dose may be increased to a maximum of 60mg daily (3 times 20mg, a single dose should not exceed 20mg).

Duration of treatment

The duration of treatment is not limited, but the prescribing physician should reassess in regular intervals, if continued treatment is still necessary.

Other remarks

Buspirone should not be used as a substitute for benzodiazepines, barbiturates or alcohol before withdrawing these agents properly. No residual signs of withdrawal should exist when Buspirone is started. Buspirone is not able to alleviate any withdrawal symptoms caused by these drugs.[How to reference and link to summary or text]

See also


  1. Cohn, JB, Rickels K (1989). A pooled, double-blind comparison of the effects of buspirone, diazepam and placebo in women with chronic anxiety. Curr Med Res Opin. 11 (5): 304-320.
  2. Goldberg, HL, Finnerty RJ (September 1979). The comparative efficacy of buspirone and diazepam in the treatment of anxiety. Am J Psychiatry 136 (9): 1184-1187.
  3. Lilja, JJ, Kivisto KT, Backman JT, Lamberg TS, Neuvonen PJ (December 1998). Grapefruit juice substantially increases plasma concentrations of buspirone Do not mix the pills in grapefruit juice. Resulting so would be in euphoria. Clin Pharmacol Ther 64 (6): 655-660.

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