Buspirone: Independent Evidence on Anxiety (GAD), Side Effects & Interactions

Table of contents

• Evidence summary
• What buspirone is
• How it works
• What it is prescribed for
• What works and what does not
• Benefits by claim
• Risks and all side effects
• All interactions
• Who should avoid buspirone
• Dosage and how to take it
• Follow the money: who makes it and who funded the evidence
• Related research
• Frequently asked questions
• Sources and funding notes

Evidence summary

Independent evidence and credibility scorecard

Independence tiers: 1 = regulator or government body; 2 = academic or Cochrane team with no declared commercial funding for the work; 3 = independent authors analysing mostly manufacturer-run trials, or minor declared industry ties; 4 = manufacturer-funded or manufacturer-authored. Credibility runs from A (highest) to D.

What buspirone is

Buspirone hydrochloride is an anxiolytic from the azaspirodecanedione (azapirone) class, ATC code N05BE01 (UK SmPC 5.1). It is chemically and pharmacologically unrelated to the benzodiazepines.

• Brand name: BuSpar. The US brand is no longer marketed: all four BuSpar products are listed as "Discontinued" (Drugs@FDA). MedlinePlus notes, "This branded product is no longer on the market. Generic alternatives may be available" (MedlinePlus).
• US approval: NDA 018731, sponsor Bristol-Myers Squibb, approved on 29 September 1986 (Drugs@FDA).
• Originator company: Bristol-Myers Squibb, whose SEC-registered business address is Princeton, New Jersey, US (SEC EDGAR). In 2003 the FTC described Bristol as "based in New York" (FTC).
• Generics: Generic-only today. openFDA lists 16 generic (ANDA) applications (openFDA query). US labels include Teva, Aurobindo, Epic and Advagen. In the UK, 5 mg, 7.5 mg and 10 mg generic tablets are listed from several licence holders (emc listing).
• Prescription status: Prescription-only in the US and UK. "Buspirone is not a controlled substance" (UK SmPC; FDA label).
• NHS information: At the time of writing, the NHS website had no buspirone medicines page (the expected address returned "page not found"), unlike most anxiety medicines.

How it works

"The mechanism of action of buspirone is unknown," says the US label. What is known is that it has a high affinity for serotonin 5-HT_1A receptors and moderate affinity for dopamine D₂ receptors. It "has no significant affinity for benzodiazepine receptors and does not affect GABA binding" (FDA label). The Cochrane review describes azapirones as "a group of drugs that work at the 5-HT1A receptor" (Chessick 2006). The UK SmPC adds that, from animal studies, it affects serotonin, noradrenaline, acetylcholine and dopamine systems (UK SmPC 5.1).

This explains its main differences from benzodiazepines:

• Less sedation: It "lacks the prominent sedative effect that is associated with more typical anxiolytics", and studies indicate it "does not produce significant functional impairment" (FDA label).
• No cross-tolerance: Because it does not act on the benzodiazepine receptor, "it will not block the withdrawal syndrome" from benzodiazepines or other sedatives. People coming off those drugs need a gradual taper before buspirone is started.
• Serotonin effects: Its serotonin activity is why it can contribute to serotonin syndrome with other serotonergic drugs.

Pharmacokinetics that matter in practice

Buspirone is absorbed quickly but undergoes "extensive first-pass metabolism" in the liver. Unchanged buspirone makes up only about 1% of drug-related material in the blood. Its average elimination half-life is about 2 to 3 hours after single doses, which is why it is taken two or three times a day (FDA label). The UK SmPC gives a range of 2 to 11 hours (UK SmPC 5.2).

• Food: Taking a dose with food raised the AUC of unchanged buspirone by 84% and peak levels by 116%. That is why labels ask people to take it consistently, always with or always without food.
• Metabolism: It is broken down mainly by CYP3A4. This one fact drives most of its interaction risks.
• Liver and kidney disease: Steady-state exposure rose 13-fold in hepatic impairment and 4-fold in renal impairment (FDA label).

What it is prescribed for

Licensed uses

Where guidelines place it

• NICE (UK), GAD: If a person chooses drug treatment, offer an SSRI, with sertraline considered first as "the most cost-effective drug". Then another SSRI or an SNRI, then pregabalin if SSRIs and SNRIs are not tolerated (NICE CG113 1.2.23–1.2.25). Buspirone does not appear in the recommendations. NICE also says there is "no evidence that either mode of treatment (individual high-intensity psychological intervention or drug treatment) is better", so the choice should follow the person's preference.
• WHO: The 2023 mhGAP guideline's anxiety recommendations address SSRIs, psychological therapy and benzodiazepines. We found no mention of buspirone in it (WHO mhGAP 2023).
• PTSD (US VA/DoD): "There is insufficient evidence to recommend for or against" buspirone, along with a list of other drugs (VA/DoD 2023, recommendation 16).
• Depression: Buspirone is not licensed for depression. The UK SmPC says it "should not be used alone to treat depression, and may potentially mask the clinical signs of depression" (UK SmPC 4.4). It has been tested as an add-on to antidepressants; see below.

In practice, buspirone tends to be considered when someone with GAD cannot take or does not want an SSRI or SNRI, or when dependence-forming drugs need to be avoided. This is a description of where it fits, not a recommendation.

What works and what does not

Benefits by claim

Generalised anxiety disorder

The only Cochrane review dedicated to azapirones for GAD included 36 randomised trials and 5,908 participants. Participants were allocated to azapirones, placebo, benzodiazepines, antidepressants, psychotherapy or kava. Its main findings (Chessick et al., Cochrane 2006; full text):

• Against placebo: Azapirones were superior. The number needed to treat on the Clinical Global Impression scale was 4.4 (95% CI 2.16 to 15.4). On the Hamilton Anxiety scale, the pooled mean difference was −4.48 points (95% CI −6.86 to −2.10), from 4 studies with 135 people. Fewer people dropped out on azapirones than on placebo (RR 0.64, 95% CI 0.47 to 0.87).
• Against benzodiazepines: "Azapirones may be less effective than benzodiazepines." More people dropped out on azapirones than on benzodiazepines (RR 1.30, 95% CI 1.01 to 1.79). In one trial (Cohn 1986), lorazepam and alprazolam each beat buspirone on HAM-A by a WMD of 1.1 points. A comparison with diazepam was inconclusive.
• Against antidepressants, kava or psychotherapy: The reviewers were "unable to conclude" whether azapirones were better.
• Who benefits: Azapirones appeared useful "particularly for those participants who had not been on a benzodiazepine".
• Duration: Studies lasted four to nine weeks, with one lasting 14 weeks. The authors said "longer term studies are needed".

How big is the effect? A 4.5-point HAM-A difference sounds meaningful, but it comes from only 135 people. The confidence interval around the NNT runs from about 2 to about 15. In other words, the true benefit could be large or quite small. The FDA label says the long-term effectiveness beyond 3 to 4 weeks "has not been demonstrated in controlled trials".

The larger and more recent 2019 Lancet network meta-analysis (89 trials, 25,441 patients) placed buspirone among drugs "found to be efficacious and well tolerated", alongside mirtazapine, sertraline, fluoxetine and agomelatine. It added that "these findings were limited by small sample sizes" (Slee et al. 2019). Duloxetine, pregabalin, venlafaxine and escitalopram had the most robust evidence. That review received no funding.

Panic disorder

A Cochrane review found only three trials (170 people), all of buspirone. None provided enough usable information on response. Buspirone had lower acceptability than placebo: more people dropped out (RR 2.13, 95% CI 1.11 to 4.07; moderate-quality evidence). Effects on agoraphobia, general anxiety and depression were uncertain (Imai et al., Cochrane 2014). Buspirone is not licensed for panic disorder in the US or UK sources we checked.

Depression (as an add-on)

The NIMH-funded STAR*D trial took 565 people with depression that had not remitted on citalopram and randomised them to add bupropion SR, and 286 to add buspirone (up to 60 mg a day). Remission rates on the Hamilton scale were similar (29.7% bupropion, 30.1% buspirone). But bupropion produced a greater reduction in self-rated symptoms (25.3% vs 17.1%), and fewer bupropion patients stopped due to intolerance (12.5% vs 20.6%) (Trivedi et al., NEJM 2006). STAR*D had no placebo arm, so it cannot say how much buspirone itself added.

A later Cochrane review of placebo-controlled trials in treatment-resistant depression found "no evidence of a benefit" from buspirone augmentation (MADRS MD −0.30, 95% CI −9.48 to 8.88; low-quality evidence). It concluded the evidence was "currently insufficient" (Davies et al., Cochrane 2019).

The placebo question

Placebo response in anxiety trials is substantial. In the 4-week US registration trials, 9% of placebo patients reported drowsiness and 3% reported dizziness (FDA label), which shows how much symptom reporting happens without an active drug. The Cochrane CGI response analysis in two studies (187 people) gave an RR of 2.35 with a confidence interval of 0.72 to 7.72, which crosses 1 (Chessick 2006). The honest summary is that buspirone probably helps some people with GAD more than placebo over a few weeks, but the size of that benefit is uncertain.

Risks and all side effects

Buspirone has no FDA boxed warning on the label we reviewed. Its main safety issues are in the warnings, contraindications and interaction sections.

Common side effects (licensing trials)

From 17 pooled 4-week placebo-controlled trials: 477 people on buspirone, 464 on placebo (FDA label). About 10% of the 2,200 people in the premarketing efficacy trials stopped because of an adverse event, most often dizziness, insomnia, nervousness, drowsiness, lightheadedness or nausea.

Cochrane side-effect ratios are from Chessick 2006, which concluded that side effects "appeared mild and non serious". The UK SmPC lists dizziness, headache and somnolence as very common, and notes that side effects "are generally observed at the beginning of drug therapy and usually subside" with continued use or a lower dose (UK SmPC 4.8).

Serious and rare risks

Dependence, withdrawal and misuse

This is buspirone's main advantage over benzodiazepines. The US label states: "In human and animal studies, buspirone has shown no potential for abuse or diversion and there is no evidence that it causes tolerance, or either physical or psychological dependence." In two double-blind studies of volunteers with a history of recreational drug or alcohol use, none could distinguish buspirone from placebo, while they showed "a statistically significant preference for methaqualone and diazepam" (FDA label). The label still asks doctors to watch people with a history of drug misuse, because it is "difficult to predict from experiments" how any CNS-active drug will be used once marketed.

Two cautions follow from this. First, buspirone "will not block the withdrawal syndrome" of benzodiazepines or other sedatives, so switching directly can unmask withdrawal (UK SmPC 4.4). Second, the UK SmPC notes that because its mechanism is not fully understood, "long-term toxicity in the CNS or other organ systems cannot be predicted".

Overdose

In volunteers, doses up to 375 mg a day produced nausea, vomiting, dizziness, drowsiness, small pupils and stomach upset. "No deaths have been reported following overdosage with buspirone hydrochloride tablets alone." Rare fatal overdoses "were invariably associated with ingestion of multiple drugs and/or alcohol" (FDA label). Any suspected overdose still needs urgent medical assessment.

All interactions

Most buspirone interactions come from CYP3A4, the liver enzyme that clears it. Figures below are from healthy-volunteer studies in the US label and UK SmPC.

Who should avoid buspirone

Contraindications

• US: hypersensitivity to buspirone; use with, or within 14 days of, an MAOI intended to treat depression; starting buspirone during treatment with linezolid or intravenous methylene blue (FDA label).
• UK: hypersensitivity; epilepsy; acute intoxication with alcohol, hypnotics, analgesics or antipsychotics; severe renal impairment (creatinine clearance of 20 ml/min or below) or severe hepatic impairment (UK SmPC 4.3).

Use with care

The UK SmPC advises care in acute narrow-angle glaucoma, myasthenia gravis, drug dependence, and a history of renal or hepatic impairment. The tablets contain lactose (UK SmPC 4.4).

Children and adolescents

Not recommended under 18. Trials did not show benefit in young people with GAD, and blood levels of buspirone and its active metabolite were higher in children than adults at the same dose (FDA label; UK SmPC).

Older adults

In one study of 6,632 patients treated for anxiety, 605 were aged 65 or over. Their safety and efficacy profiles "were similar to those in the younger population", and age did not change buspirone's pharmacokinetics. Still, "greater sensitivity of some older patients cannot be ruled out" (FDA label). Buspirone does not appear in the tables of the 2023 AGS Beers Criteria, which list benzodiazepines as drugs to avoid in older adults (AGS Beers 2023). Absence from Beers is not proof of safety; it means the panel did not flag it. Dizziness, the most common side effect, still matters for falls.

Pregnancy and breastfeeding

• Pregnancy: Human data are limited. Animal studies at about 30 times the maximum human dose showed no fetal harm. The US label says it should be used in pregnancy "only if clearly needed" (FDA). The UK SmPC says, "As a precautionary measure, it is preferable to avoid the use of buspirone during pregnancy" (UK SmPC 4.6).
• Breastfeeding: It is not known whether buspirone passes into human milk, although it does in rats. The US label says use while nursing "should be avoided if clinically possible".

Liver and kidney disease

Blood exposure rose 13-fold in hepatic impairment and 4-fold in renal impairment (FDA). The UK SmPC advises caution and low, twice-daily dosing in mild to moderate renal impairment, careful titration in cirrhosis, and no use at creatinine clearance below 20 ml/min (UK SmPC 4.2).

Dosage and how to take it

Your prescriber sets the dose. The ranges below are the official licensed adult ranges, provided for context only. They are not a guide to self-dosing.

Note that the US maximum (60 mg) is higher than the UK maximum (45 mg). Lower starting doses are advised with strong CYP3A4 inhibitors and in kidney or liver impairment.

How to take it

Take buspirone at the same times each day and consistently either with or without food, because food changes how much is absorbed (UK SmPC). Avoid large amounts of grapefruit or grapefruit juice (MedlinePlus).

How long before it works

Buspirone is not a rescue medicine. The dose is increased no more often than every 2 to 3 days, and "it may take several weeks before you reach a dose that works for you" (MedlinePlus). Its efficacy trials measured results over 3 to 4 weeks or more (FDA label). This slower onset is one reason people used to the rapid effect of a benzodiazepine may feel it is not working. That may be why Cochrane found it appeared more useful in people who had not taken benzodiazepines (Chessick 2006).

How long to take it

The UK licence is for "short-term management". The US label says the doctor using it for extended periods "should periodically reassess the usefulness of the drug for the individual patient".

How to stop

Neither the US label nor the UK SmPC we reviewed describes a withdrawal syndrome for buspirone itself, and neither sets out a taper schedule. Stopping should still be planned with your prescriber, both to watch for returning anxiety and to manage any other medicines. The opposite situation is more important: if you are coming off a benzodiazepine, that drug must be tapered separately, because buspirone will not cover its withdrawal.

Driving

The UK SmPC says buspirone has "moderate influence on the ability to drive and use machines" because of drowsiness or dizziness, and includes the standard UK drug-driving statutory-defence wording (UK SmPC 4.7). Do not drive until you know how it affects you.

Follow the money: who makes it and who funded the evidence

Who made it, and who sells it now

• Originator: Bristol-Myers Squibb (US). Its original application was approved on 29 September 1986 (Drugs@FDA). Its current SEC business address is Princeton, New Jersey (SEC EDGAR).
• Sales at peak: "In 2000, the last full year before generic entry, Bristol's U.S. sales of BuSpar were over $600 million" (FTC 2003).
• Today: The brand is discontinued in the US, and buspirone is sold only as generics by many manufacturers, including Teva Pharmaceuticals USA, Aurobindo (whose UK arm Milpharm holds the SmPC we used), Epic and Advagen (openFDA; UK SmPC). No company has a strong commercial incentive to promote buspirone today. That also means no company is funding new trials of it.

Documented integrity event: the BuSpar generic-delay case

In March 2003 the US Federal Trade Commission announced that Bristol-Myers Squibb had settled charges that it engaged in "a series of anticompetitive acts over the past decade to obstruct the entry of low-price generic competition" for three products: Taxol, Platinol and BuSpar (FTC 2003). For BuSpar, the FTC complaint alleged that:

• Bristol submitted a patent for listing in the FDA's Orange Book "literally hours before generic rivals were set to enter the market", which triggered automatic delays to generic approval.
• Bristol "paid its potential buspirone rival over $70 million to withhold competition until patent expiration".

The consent order barred Bristol from re-listing the patent at issue and restricted similar conduct. Separately, New York, Texas and Maryland led a coalition of 35 other states, the District of Columbia and Puerto Rico in an antitrust suit charging that Bristol "illegally maintained its monopoly over BuSpar". Bristol had agreed in principle to pay the states up to $100 million, and the settlement created a $41 million nationwide consumer fund (which also included money from private class actions) for people who bought BuSpar from 1 January 1998 to 31 January 2003 (New York Attorney General, March 2003). These were settlements of allegations, not court findings after trial. They concern pricing and competition, not the drug's safety or the accuracy of its trials.

Who funded the evidence

• Original trials: The US label's efficacy and safety data come from the premarketing programme of more than 3,500 subjects submitted by the original sponsor. The Cochrane review records that several included trials were "Supported by Bristol-Meyers Squibb" [sic], and one comparison with venlafaxine was "Supported by Wyeth-Ayerst Research" (Chessick 2006, characteristics of included studies).
• The main GAD review: Supported internally by CNPq (Brazil's national research council) and the University of Colorado, with no external sources and author declarations of "None". However, the current Cochrane record carries a notice that "the current version of this review contravenes Cochrane's commercial sponsorship policy (revised 2014)", and says an update by a compliant team was scheduled for 2016 (Chessick 2006). We did not find a published update in PubMed. That means the main systematic review of buspirone for GAD is now 20 years old.
• Newer independent work: Slee 2019 had no funding. The panic and treatment-resistant depression Cochrane reviews were academic. STAR*D was funded by the US National Institute of Mental Health (Trivedi 2006).
• Cochrane's rule: Reviews "cannot be funded or conducted by commercial sponsors or commercial sources with a real or potential vested interest in the findings" (Cochrane policy).

What this means: Buspirone's benefit for GAD was established mainly by its maker's trials in the 1980s and 1990s. Independent reviewers who pooled those trials, and a later unfunded network meta-analysis, broadly confirmed a modest short-term benefit. Its reputation for low dependence risk rests on the manufacturer's abuse-liability studies, as summarised by regulators, and we found no independent evidence contradicting it. Because buspirone is now a cheap generic, the evidence gap (no modern, long, independent trials) is unlikely to be filled by industry.

Related research

For wider, evidence-graded context, see these Pure City Research guides:

• Stress, anxiety and depression: prevention and management guide
• Supplements for stress, anxiety and depression: the evidence
• L-theanine
• Magnesium
• Ashwagandha: evidence and safety
• St John's wort (interacts with buspirone)
• Saffron for depression: the evidence

Sibling medicine reviews:

• Sertraline
• Escitalopram
• Venlafaxine
• Duloxetine
• Pregabalin
• Hydroxyzine
• Clonazepam
• Diazepam
• Bupropion

Frequently asked questions

Sources and funding notes

• FDA-approved prescribing information, buspirone hydrochloride tablets (Teva; DailyMed, effective July 2023): US regulator-approved generic label. Efficacy and abuse-liability data derive from the original BuSpar programme.
• Drugs@FDA, NDA 018731 (BuSpar): US FDA database. Approved 29 September 1986; sponsor Bristol-Myers Squibb; all products discontinued.
• openFDA Drugs@FDA query (generic applications): US government data (16 ANDAs at time of checking).
• Buspirone Hydrochloride 10 mg Tablets, UK SmPC: MHRA-approved; licence holder Milpharm Ltd (Aurobindo group). Text revised 24 July 2026.
• MedlinePlus: Buspirone: US National Library of Medicine; content from ASHP (AHFS). Last revised 15 March 2026.
• NICE CG113: Generalised anxiety disorder and panic disorder in adults: UK government-funded guideline. Accessed via archived copy (September 2026) because the live page blocked automated access.
• WHO mhGAP guideline, 3rd edition (2023): World Health Organization.
• VA/DoD PTSD guideline, Provider Summary (June 2023): US government.
• Chessick CA et al. Azapirones for generalized anxiety disorder. Cochrane 2006 (full text): US/Brazil. Internal support from CNPq and the University of Colorado; declarations "None"; flagged by Cochrane as contravening its 2014 commercial sponsorship policy. Several included trials were supported by Bristol-Myers Squibb.
• Slee A et al. Pharmacological treatments for generalised anxiety disorder. Lancet 2019: UCL (UK). "No funding was received."
• Imai H et al. Azapirones versus placebo for panic disorder in adults. Cochrane 2014: Japan/Italy. Most authors no conflicts; two declared lecture fees from Eli Lilly and others.
• Trivedi MH et al. Medication augmentation after the failure of SSRIs for depression (STAR*D). NEJM 2006: US. Funded by NIMH contract N01MH90003.
• Davies P et al. Pharmacological interventions for treatment-resistant depression in adults. Cochrane 2019: University of Bristol (UK). One author declared pharma lecture payments.
• Ipser JC et al. Pharmacotherapy for anxiety and comorbid alcohol use disorders. Cochrane 2015: South Africa. Later found by Cochrane's Funding Arbiters to be non-compliant with its conflict-of-interest policy.
• American Geriatrics Society 2023 Beers Criteria: US professional society; "There was no sponsor for this paper." Buspirone is not listed.
• US Federal Trade Commission press release, March 2003: US government enforcement record (settled charges).
• New York Attorney General: Settlement in BuSpar case submitted to the court (7 March 2003): US state government.
• SEC EDGAR: Bristol-Myers Squibb company record: US government filing data (business address).
• Cochrane commercial sponsorship policy: Cochrane (UK/international).
• electronic medicines compendium (emc) buspirone listing: UK product information database. Used to identify UK licence holders.

Last reviewed: 26 September 2026. Educational information from Pure City Research, not medical advice. Medicine decisions belong with a qualified prescriber.