Buspirone (BuSpar) is the first example of a class
of anxiolytic agents that can relieve some symptoms of anxiety in doses that do
not cause sedation. Buspirone is structurally unrelated to existing
Although buspirone has been
shown to interact with a number of neurotransmitter systems in the brain, it
ap-pears that its clinically relevant effects are mediated through interactions
at the serotonin (5-hydroxytrypta-mine, 5-HT) 5-HT1A receptor, where
it acts as a partial agonist.
Buspirone is well absorbed
from the gastrointestinal tract, and peak blood levels are achieved in 1 to 1.5
hours; the drug is more than 95% bound to plasma pro-teins. Buspirone is
extensively metabolized, with less than 1% of the parent drug excreted into the
urine un-changed. At least one of the metabolic products of bus-pirone is
biologically active. The parent drug has an elimination half-life of 4 to 6
Buspirone is as effective as the benzodiazepines in the treatment
of general anxiety. However, the full anxiolytic effect
of buspirone takes several weeks to develop, whereas the anxiolytic effect of
the benzodiazepines is maximal after a few days of therapy. In therapeutic
doses, buspirone has little or no sedative effect and lacks the muscle relaxant
and anticonvulsant properties of the benzodiazepines. In addition, buspirone
does not potentiate the central nervous system depression caused by
sedativeâ€“hypnotic drugs or by alcohol, and it does not prevent the symptoms
associated with benzo-diazepine withdrawal.
Buspirone is effective in
general anxiety and in anxiety with depression.
Like the benzodiazepines,
buspirone appears to be safe even when given in very high doses. The most
common side effects are dizziness, light-headedness, and head-ache. Abuse,
dependence, and withdrawal have not been reported, and buspirone administration
does not pro-duce any cross-tolerance to the benzodiazepines. Bus-pirone has
been reported to increase blood pressure in patients taking monoamine oxidase
inhibitors, and it may increase plasma levels of haloperidol if coadminis-tered
with that agent.