Buspirone generally is well tolerated. A causal relationship between many adverse reactions and the drug has not been established but cannot be excluded.
In controlled studies, the incidence of some adverse effects was similar in patients receiving Buspirone or placebo.
Nervous system effects (e.g., dizziness, headache, drowsiness, light-headedness) are the most common adverse effects of Buspirone,but those secondary to CNS depression (e.g., sedation, psychomotor dysfunction) generally occur less frequently than with other currently available anxiolytics (e.g., benzodiazepines).

In clinical studies, adverse reactions requiring discontinuance of Buspirone therapy occurred in about 10% of patients and included nervous system effects (e.g., dizziness, insomnia, nervousness, drowsiness, light-headedness, headache, fatigue) and GI effects (e.g., nausea).

There is some evidence that tolerance of Buspirone‘s adverse effects (e.g., dizziness) may be slightly less in geriatric patients than in younger adults.
The incidence and severity of adverse reactions to Buspirone relative to dosage and duration of therapy have not been fully characterized; however, adverse effects appear to occur more frequently at increasing dosagesbut generally appear to diminish with time during continued therapy. Because Buspirone can bind to central dopamine receptors,the possibility exists that chronic therapy could result in adverse effects secondary to changes in dopamine-mediated neurologic function.(See Cautions: Nervous System Effects.) Although clinical experience to date has failed to reveal substantial evidence of such long-term effects at usual dosages,the possibility of risk cannot be ruled out and additional experience is needed to determine Buspirone‘s potential for long-term sequelae.

Nervous System Effects

The most frequent adverse effects associated with Buspirone therapy are nervous system effects.

The most frequent adverse effects associated with Buspirone therapy are nervous system effects.In controlled studies, dizziness,drowsiness,and headacheoccurred in about 10% of patients; fatigue, nervousness,insomnia, and light-headednessoccurred in about 5%; and excitement, depression, decreased concentration, nightmares/vivid dreams, anger/hostility, confusion, weakness, incoordination, paresthesia, numbness, and tremoroccurred less frequently.

In these studies, dizziness, headache, nervousness, light-headedness, paresthesia, and excitement occurred appreciably more frequently in patients receiving Buspirone than in those receiving placebo. Insomnia and nervousness may become particularly evident at high dosages (e.g., 100 mg daily), and may be secondary to a dose-dependent stimulation of α-adrenergic (noradrenergic) cells of the locus ceruleus.

Buspirone is relatively nonsedating compared with other currently available anxiolytics (e.g., benzodiazepines),although sedative effects (e.g., drowsiness, lethargy, sedation) may become more prominent as dosage is increased (e.g., at dosages exceeding 20 mg daily).
In addition, Buspirone‘s sedative effects often are most apparent during initiation of therapy or upward titration of dosage and tend to decrease with time. However, the drug’s CNS effects show interindividual variation and the potential for their development may not be predictable in a given patient. Adverse effects resulting from CNS and psychomotor depression (e.g., drowsiness, fatigue, mental depression, confusion, decreased concentration, incoordination, weakness) generally occur less frequently with Buspirone than with benzodiazepines (e.g., clorazepate, diazepam, lorazepam),while dizziness, headache, nervousness, and paresthesia generally occur more frequently with Buspirone.

Dream disturbances occur in at least 1% of patients receiving Buspirone, but a causal relationship to the drug has not been established.

Other adverse nervous system effects not directly attributed to the drug but occurring less frequently include depersonalization, dysphoria, noise intolerance, euphoria, fearfulness, loss of interest, dissociative reaction, hallucinations, suicidal ideation, and seizures. Claustrophobic feelings, cold intolerance, stupor, slurred speech, and psychosisoccur rarely.
Depressionand increased appetiteoccasionally have emerged during chronic (i.e., 6 months or longer) therapy with the drug. Buspirone‘s potential for causing acute and chronic changes in dopamine-mediated neurologic function (e.g., dystonia, parkinsonian-like manifestations, akathisia, tardive dyskinesia) has not been fully elucidated.

Clinical experience to date suggests that the risk for such effects during Buspirone therapy at usual anxiolytic dosages is minimal,and such experience has not revealed evidence of definitive extrapyramidal reactions directly attributable to the drug. However, akathisia, hypertonia, dystonia, tremor, involuntary movements, slowed reaction time, and rigid/stiff musclesreportedly have been associated with anxiolytic dosages of Buspirone in a few patients. In addition, a syndrome of restlessness, appearing shortly after initiation of therapy with the drug, has been reported occasionally. This syndrome may have resulted from increased central α-adrenergic activity or from dopaminergic or other effects.

In addition, extrapyramidal manifestations (e.g., akathisia, tremor, rigidity) also have occurred in at least one patient receiving a Buspirone hydrochloride dosage substantially exceeding usual anxiolytic dosages. In a limited number of patients with parkinsonian syndrome, dosages of 10-70 mg daily caused no clinically important deterioration in manifestations of the syndrome, although some deterioration (e.g., in functional ability) was apparent at relatively high dosages (e.g., 90-100 mg daily).

Myoclonus, which may have been serotonergically mediated, also has been reported in at least one patient shortly after initiation of usual anxiolytic dosages of Buspirone; the myoclonus resolved following discontinuance of the drug and administration of clonazepam.Increased anxiety, agitation, and restlessness accompanied by pressured speech and racing thoughts occurred in several patients with panic disorder or generalized anxiety disorder who were receiving Buspirone with tricyclic antidepressants and/or alprazolam; these manifestations resolved within 1-5 days following discontinuance of Buspirone therapy.

Hypomania also has been reported in a patient with bipolar disorder and symptoms of anxiety concurrently receiving Buspirone, lithium, tranylcypromine, and alprazolam; symptoms of hypomania resolved within 3 days following discontinuance of Buspirone therapy in this patient. Although the mechanism is unclear, it has been suggested that these reactions may have been caused by a Buspirone-induced increase in dopaminergic or α-adrenergic activity, effects of the drug on 5-HT1 receptors, and/or a possible drug interaction between Buspirone and alprazolam.

More Frequent:

DIZZINESS
HEADACHE
NAUSEA
NERVOUSNESS

Rare or Very Rare:

BLURRED VISION
CHEST PAIN
CONCENTRATION DIFFICULTY
CONFUSION
DEPRESSION
DREAMS OR NIGHTMARES
DROWSINESS
DRY MOUTH
FATIGUE
FEVER
INSOMNIA
MUSCLE SPASM WITH PAIN
MUSCLE WEAKNESS
PARESTHESIA
POUNDING PULSE
SORE THROAT
TACHYCARDIA
TINNITIS