Medication approval journey

buspirone (BuSpar)

Approved for Generalized anxiety disorder

FDA approvedOther anti-anxiety medicationTaper risk: low

Before changing anything

Low risk from stopping, but still worth planning

Withdrawal risk in this group is generally low, but dose changes are still worth discussing rather than improvising.

How long the trials actually ran

We could not establish a longest trial length for buspirone. That is a gap in what we can show you — not evidence that the trials ran long.

This application has been through the modern labelling rules, and the marketed labels still carry no clinical studies section at all.

The gap between how long the trials ran and how long people actually take these medications is the single most important thing on this page. It is not evidence that longer use is unsafe or ineffective. It is evidence that longer use was not what got tested.

How many Americans take buspirone

Survey-based federal estimates, published with a lag of about two years. They count prescriptions filled, not outcomes.

16,706,971
prescriptions in the United States (2024)
3,719,958
people filling them (2024)

Prescriptions are up 121% since 2014. Whatever you decide about buspirone, you are deciding alongside about 3,719,958 other people this year.

Source: ClinCalc DrugStats (Medical Expenditure Panel Survey (MEPS), Agency for Healthcare Research and Quality), CC BY-SA 4.0, release 2026.08.

What people report to the FDA about buspirone

Read this before the numbers.

Anyone can file an adverse event report — patients, doctors, manufacturers — and nobody verifies that the drug caused what was reported. There is no denominator: tens of millions of prescriptions generate reports at an unknowable rate, and reporting rises with news coverage, not necessarily with harm. Counts below are report volumes, not rates, and cannot be compared between drugs. The FDA itself says not to use this data to make medical decisions — we show it because you deserve to see what is in the public record, with its limits stated plainly.

10,969
reports mentioning buspirone, all time
6,088
filed as serious (a report-level flag covering every drug and outcome in the report)

Most-reported reactions

  • Fatigue800
  • Nausea798
  • Headache731
  • Drug ineffective670
  • Anxiety668
  • Dyspnoea583
  • Pain578
  • Diarrhoea511
  • Depression503
  • Dizziness500

“Drug ineffective” ranking this high is worth noticing: a report of not being helped counts as an adverse event too, and people file them in large numbers.

Source: FDA Adverse Event Reporting System (FAERS), via openFDA, data through 2026-07-30.

Known interactions, from the label

The FDA label’s interactions section, verbatim. A pharmacist checking your actual medication list beats any published list — including this one.

Read the label’s interactions section

Drug Interactions Psychotropic Agents MAO inhibitors The use of monoamine oxidase inhibitors (MAOIs) intended to treat depression with buspirone or within 14 days of stopping treatment with buspirone is contraindicated because of an increased risk of serotonin syndrome and/or elevated blood pressure. The use of buspirone within 14 days of stopping an MAOI intended to treat depression is also contraindicated. Starting buspirone in a patient who is being treated with reversible MAOIs such as linezolid or intravenous methylene blue is also contraindicated because of an increased risk of serotonin syndrome (see WARNINGS , DOSAGE AND ADMINISTRATION AND CONCOMITANT DRUG ). Amitriptyline After addition of buspirone to the amitriptyline dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (C max , AUC, and C min ) of amitriptyline or its metabolite nortriptyline were observed. Diazepam After addition of buspirone to the diazepam dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (C max , AUC, and C min ) were observed for diazepam, but increases of about 15% were seen for nordiazepam, and minor adverse clinical effects (dizziness, headache, and nausea) were observed. Haloperidol In a study in normal volunteers, concomitant administration of buspirone and haloperidol resulted in increased serum haloperidol concentrations. The clinical significance of this finding is not clear. Nefazodone (See Inhibitors and Inducers of Cytochrome P450 3A4 (CYP3A4) ) Trazodone There is one report suggesting that the concomitant use of trazodone hydrochloride and buspirone may have caused 3 to 6-fold elevations on SGPT (ALT) in a few patients. In a similar study attempting to replicate this finding, no interactive effect on hepatic transaminases was identified. Triazolam/Flurazepam Coadministration of buspirone with either triazolam or flurazepam did not appear to prolong or intensify the sedative effects of either benzodiazepine. Other Psychotropics Because the effects of concomitant administration of buspirone with most other psychotropic drugs have not been studied, the concomitant use of buspirone with other CNS-active drugs should be approached with caution. Inhibitors and Inducers of Cytochrome P450 3A4 (CYP3A4) Buspirone has been shown in vitro to be metabolized by CYP3A4. This finding is consistent with the in vivo interactions observed between buspirone and the following: Diltiazem and Verapamil In a study of nine healthy volunteers, coadministration of buspirone (10 mg as a single dose) with verapamil (80 mg t.i.d.) or diltiazem (60 mg t.i.d.) increased plasma buspirone concentrations (verapamil increased AUC and C max of buspirone 3.4-fold while diltiazem increased AUC and C max 5.5-fold and 4-fold, respectively). Adverse events attributable to buspirone may be more likely during concomitant administration with either diltiazem or verapamil. Subsequent dose adjustment may be necessary and should be based on clinical assessment. Erythromycin In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with erythromycin (1.5 g/day for 4 days) increased plasma buspirone concentrations (5-fold increase in C max and 6-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to buspirone. If the two drugs are to be used in combination, a low dose of buspirone (e.g., 2.5 mg b.i.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment. Grapefruit Juice In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with grapefruit juice (200 mL double-strength t.i.d. for 2 days) increased plasma buspirone concentrations (4.3-fold increase in C max ; 9.2-fold increase in AUC). Patients receiving buspirone should be advised to avoid drinking such large amounts of grapefruit juice. Itraconazole In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with itraconazole (200 mg/day for 4 days) increased plasma buspirone concentrations (13-fold increase in C max and 19-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to buspirone. If the two drugs are to be used in combination, a low dose of buspirone (e.g., 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment. Nefazodone In a study of steady-state pharmacokinetics in healthy volunteers, coadministration of buspirone (2.5 or 5 mg b.i.d.) with nefazodone (250 mg b.i.d.) resulted in marked increases in plasma buspirone concentrations (increases up to 20-fold in C max and up to 50-fold in AUC) and statistically significant decreases (about 50%) in plasma concentrations of the buspirone metabolite 1-PP. With 5 mg b.i.d. doses of buspirone, slight increases in AUC were observed for nefazodone (23%) and its metabolites hydroxynefazodone (HO-NEF) (17%) and meta-chlorophenylpiperazine (9%). Slight increases in C max were observed for nefazodone (8%) and its metabolite HO-NEF (11%). Subjects receiving buspirone 5 mg b.i.d. and nefazodone 250 mg b.i.d. experienced lightheadedness, asthenia, dizziness, and somnolence, adverse events also observed with either drug alone. If the two drugs are to be used in combination, a low dose of buspirone (e.g., 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment. Rifampin In a study in healthy volunteers, coadministration of buspirone (30 mg as a single dose) with rifampin (600 mg/day for 5 days) decreased the plasma concentrations (83.7% decrease in C max ; 89.6% decrease in AUC) and pharmacodynamic effects of buspirone. If the two drugs are to be used in combination, the dosage of buspirone may need adjusting to maintain anxiolytic effect. Other Inhibitors and Inducers of CYP3A4 Substances that inhibit CYP3A4, such as ketoconazole or ritonavir, may inhibit buspirone metabolism and increase plasma concentrations of buspirone while substances that induce CYP3A4, such as dexamethasone or certain anticonvulsants (phenytoin, phenobarbital, carbamazepine), may increase the rate of buspirone metabolism. If a patient has been titrated to a stable dosage on buspirone, a dose adjustment of buspirone may be necessary to avoid adverse events attributable to buspirone or diminished anxiolytic activity. Consequently, when administered with a potent inhibitor of CYP3A4, a low dose of buspirone used cautiously is recommended. When used in combination with a potent inducer of CYP3A4 the dosage of buspirone may need adjusting to maintain anxiolytic effect. Other Drugs Cimetidine Coadministration of buspirone with cimetidine was found to increase C max (40%) and T max (2 fold), but had minimal effects on the AUC of buspirone.

FDA label for buspirone, effective August 27, 2026 — DailyMed.

Who pays for buspirone

Two claims datasets and one survey, covering different populations with different instruments — they cannot be reconciled by arithmetic, and where their sum crowds the all-payer estimate, that is a finding about the estimates rather than a percentage.

Medicare Part D · claims · 2024Medicaid · claims floor · 2024All-payer · survey · 2024Commercially insured adults · not publishedChildren · no per-drug data
Medicare Part D
Read the under-65 group correctly before the numbers: Medicare before 65 means the disabled and dual-eligible population — among the sickest, highest-need people in the program — and reading their utilization as typical adult use would be a category error. The beneficiary total sums brand-level rows, so treat it as an upper bound on distinct people. 1,553,798 beneficiaries filled 7,844,181 claims in 2024 — 1,138,520 aged 65 and over, and 415,278 under 65.
Medicaid
At least 5,245,157 prescriptions in 2024 — a floor, because 198 of 1,144 national data rows are suppressed for privacy and contribute zero. Medicaid covers more children than any insurer in the country and publishes no age split — how much of this number is pediatric use is not knowable from public data.
All payers (survey estimate)
The MEPS-based estimate above puts the whole country at 16,706,971 prescriptions and 3,719,958 people in 2024. Subtracting the public programs from it would produce a number for everyone else — and we do not print that number, because subtracting a survey from claims counts manufactures precision that does not exist.
The population nobody counts
The commercially insured working-age adult — statistically, the likeliest person to be reading this page — is the one population with no public per-drug count anywhere. Private claims data exists and is sold, but nothing a patient can check is published. For children the record is thinner still: no public source counts pediatric use of buspirone specifically; the closest the public record comes is condition-level treatment rates for children, which we have traced for one condition in how childhood ADHD got counted.

Sources: Medicare Part D Prescribers — by Geography and Drug, data.cms.gov, National rows, data year 2024 (published with ~17-month lag). Medicaid State Drug Utilization Data 2024, data.medicaid.gov, national aggregate rows. Retrieved 2026-09-01.

The approval, step by step

  1. Step 1

    What the approval was actually based on

    Which studies did the FDA rely on, how long did they run, and who was in them?

    read the label on DailyMed

    Our reading

    There is no clinical studies section on this label. Not a short one — none. Buspirone is the harder case of the three, because it cannot be waved away as an old label: an efficacy supplement was filed against this application in 2001, after the Physician Labeling Rule took effect, and the marketed labels still carry no section 14. Buspirone is widely prescribed precisely because it is not a benzodiazepine — no dependence, no sedation, no controlled-substance schedule. That is a genuine and important advantage. It is also an argument about what buspirone does not do, and it is the argument you will hear instead of an efficacy figure.

  2. Step 2

    The approval

    When was it approved, under what application, and by whose review?

    Approved
    September 29, 1986
    Application
    NDA018731
    Review
    PRIORITY
    Original sponsor
    Bristol-Myers Squibb
    Holds it now
    Bristol-Myers Squibb
    Label submissions since
    39

    Source: openFDA Drugs@FDA, original application ORIG-1

  3. Step 3

    What was added after it was on the market

    Which warnings arrived only after millions of people were already taking it?

    We have not recorded a post-approval change to the buspirone label. That is the state of our record, not a finding that nothing was ever added.

  4. Step 4

    What independent research has found since

    What has been learned by people who were not selling it?

  5. Step 5

    What still is not known

    Which questions you might reasonably have has nobody answered yet?

    • A priority review in 1986 and still no trial section on the label forty years later. What would it take to find out how well it works?
    • Most of what makes buspirone attractive is what it lacks — dependence, sedation, abuse potential. Is it being compared against alternatives on benefit, or only on harm?
    • It is often described as taking weeks to work. Over what period was that established, and by whom?

Deciding about buspirone?

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