Butea superba (red kwao krua)

Also called red kwao krua, red kwao khruea, red gwow kreur, Butea superba Roxb..

Best grade D across 2 graded outcomes Botanical Last checked

The short answer

From 11 sources

Butea superba (red kwao krua) is a Thai tuber marketed as a male potency herb. There is no reliable placebo-controlled evidence that it improves erections: the one placebo trial lost its whole placebo group, and a product that matched sildenafil turned out to contain a sildenafil-type drug. FDA warns that sexual-enhancement products often hide prescription drugs.

Every graded outcome on this page

2 rows · line = participants
  1. Grade DErectile function (IIEF-5) with a lost placebo groupSexual functionn 39
  2. No effectErectile function (IIEF-5) vs sildenafil, then vs starchSexual functionn 32

Key facts

Placebo arm collapsed
In the only randomized placebo trial, every placebo participant dropped out by week 3, leaving only a before-and-after comparison in the 17 men given Butea111
Adulterated batch
A Butea product that matched sildenafil was most likely blended with a sildenafil-type drug; a second batch showed no effect versus starch2
FDA warning
FDA says many products sold for sexual enhancement are likely contaminated with dangerous hidden ingredients9
Hormone effects
A 35-year-old man had raised dihydrotestosterone after a few weeks of Butea capsules; it normalised a week after stopping3
Animal toxicity
90 days of high-dose tuber powder lowered testosterone and raised liver enzymes in male rats4

What it is

Butea superba is a plant of Thailand and India whose tuberous roots, known in Thailand as red kwao krua, are sold as a male potency supplement.

How it works

Proposed

Butea superba tubers contain flavonoids reported to inhibit cAMP phosphodiesterase, which the 2003 trial authors proposed could relax erectile tissue. In rats the tuber shows androgenic activity and can lower luteinising hormone or testosterone. None of this is confirmed in people.11674

Forms, side by side

2 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.

Butea superba (red kwao krua) forms compared

2 forms
Butea superba (red kwao krua) forms compared: 2 forms by 3 attributes. Empty cells are labelled No data yet, or Not graded in the evidence row.
2 formsDried tuber powder capsulesCommercial Butea superba products
Absorption in peopleNot studied.11Not studied.29
GI toleranceNo changes in blood counts, chemistry or testosterone in 17 men over 3 months (small and uncontrolled).11Batches can be adulterated with prescription PDE5 inhibitors; FDA warns this category often hides drugs.29
Studied forErectile dysfunctionSexual enhancement marketing
  1. Dried tuber powder capsules
    Absorption in people
    Not studied.11
    GI tolerance
    No changes in blood counts, chemistry or testosterone in 17 men over 3 months (small and uncontrolled).11
    Studied for
    Erectile dysfunction
  2. Commercial Butea superba products
    Absorption in people
    Not studied.29
    GI tolerance
    Batches can be adulterated with prescription PDE5 inhibitors; FDA warns this category often hides drugs.29
    Studied for
    Sexual enhancement marketing
Every cell holds data from a cited page; citation numbers link to the page that holds them.Scroll the table for every column

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

2 graded outcomes, largest study first

2 graded outcomes: 1 mixed, 1 no effect. The largest, a 2003 randomized trial of 39 people on erectile function (IIEF-5) with a lost placebo group, found mixed results.

1. Erectile function (IIEF-5) with a lost placebo group: mixed, 39 people1
2. Erectile function (IIEF-5) vs sildenafil, then vs starch: no effect, 32 people2

1Erectile function (IIEF-5) with a lost placebo group

Mixed · Grade D · RCT, 39 people, 2003

Thai men aged 30 to 70 with erectile dysfunction for at least 6 months

Dose, result and source
Every graded outcome on this page, largest study first
OutcomeFoundPeopleStudyWho was studied
Erectile function (IIEF-5) with a lost placebo groupMixed39Grade D · RCT, 2003Thai men aged 30 to 70 with erectile dysfunction for at least 6 months
Erectile function (IIEF-5) vs sildenafil, then vs starchNo effect32No-effect grade · Open-label trial, 2010Men with organic erectile dysfunction
Each circle is one graded outcome on this page, numbered from the largest study down, and placed by how many people it studied (log scale). It shows who was studied and what was found, not advice about your dose.

Every graded row

2 rows
Grade DErectile function (IIEF-5) with a lost placebo groupSexual functionUnreliable: no placebo comparisonRCT
n 39 · 2003

Mixed Among men given Butea, 4 of 5 IIEF-5 items improved from baseline and 14 of the 17 men who finished (82.4%) reported some improvement. All placebo participants had dropped out by week 3, so no comparison with placebo was possible. Blood counts, blood chemistry and testosterone did not change.

Design
RCT, n = 39, 2003
Population
Thai men aged 30 to 70 with erectile dysfunction for at least 6 months
Form
Dried Butea superba tuber powder capsules (250 mg) vs tapioca-starch placebo
Dose
1,000 mg/day (500 mg/day for the first 4 days)
Duration
3 months
Source
Reference 1 · PubMed 12937809 (opens PubMed)
No effectErectile function (IIEF-5) vs sildenafil, then vs starchSexual functionNo effect once adulteration excludedOpen-label trial
n 32 · 2010

No effect In the open phase, 84% responded to the first Butea batch vs 81% to sildenafil. In the double-blind phase the second batch had no effect. The authors concluded the first batch was most likely blended with a PDE5 inhibitor, which the supplier later confirmed.

Design
Open-label trial, n = 32, 2010
Population
Men with organic erectile dysfunction
Form
Butea superba 'natural health' product vs sildenafil 50 mg; responders then received a second Butea batch or starch (double-blind)
Dose
100 mg Butea superba product
Duration
Short-term, with a 1-week washout
Source
Reference 2 · PubMed 19624593 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

No reliable human efficacy data

The 2003 trial lost its entire placebo group and the 2010 study found no effect from a clean batch, so there is no valid placebo-controlled evidence that Butea superba improves erections. A 2011 review called the human trials not robust.12811

How we got this: Evidence table on this page

Testosterone claims are not supported in people

Testosterone did not change in the 17 men who finished the 2003 trial; in rats, high doses lowered it.114

How we got this: 2003 trial full text and rat study

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 100 mg of an extract product (open-label study; schedule not given in the abstract) to 1,000 mg/day of dried tuber powder for 3 months. These are research doses, not recommendations.211

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

What Butea superba meets

2 cited rows

Medicines 2

Butea superba2 medicines · 0 supplements

Supplements and foods 0

No supplement rows in our sources.

  • Drug label or FDA notice
  • Case reports
Rows as our evidence profiles cite them; links stay on this site. Line weight shows what backs a row, not how serious an interaction is. No line means none was found in our sources, not that a combination is safe. Not medical advice: ask your pharmacist.

Interactions

2 agents
Published interactions, grouped by kind
AgentWhat the source saysEvidence
Medicines2
Nitrates (for example nitroglycerin)Sexual-enhancement products have contained undeclared sildenafil, which FDA warns may interact with nitrates and lower blood pressure to dangerous levels; one Butea batch tested in a study was adulterated with a PDE5 inhibitor.102FDA safety communication
Hormone therapies (testosterone, anti-androgens)Butea superba showed androgenic activity in rats and was linked to raised dihydrotestosterone in one man; use with hormone drugs has not been studied.36Case report

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Butea superba and your picks, and between your picks.

Most cited:

Add a supplement or medicine you take to check it against Butea superba.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Not medical advice, and no dosing advice. An empty result means no row we cite names that pair, by name or through a drug class we can link the medicine to, not that a combination is safe. Where our sources name only a group of medicines we cannot match, the cabinet says so. Ask your pharmacist before you combine supplements and medicines.

Who should be careful

4 groups
People who use nitrates or have heart disease
Products sold for sexual enhancement can hide sildenafil-type drugs that FDA warns may drop blood pressure dangerously with nitrates, which people with diabetes, high blood pressure, high cholesterol or heart disease often use.1092
Women, including during pregnancy and breastfeeding
Butea superba had androgenic effects on the uterus of female rats, and there are no human safety data in women, in pregnancy or during breastfeeding (LactMed has no entry).6
People with hormone-sensitive conditions
One man had raised dihydrotestosterone while using Butea capsules, and high-dose rat studies showed testosterone and luteinising hormone changes.347
People with liver concerns
High doses raised the liver enzymes ALP and AST in male rats over 90 days.4
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.

Hidden drugs and hormone effects

4 notes

Products in this category are often adulterated.

FDA warning
FDA states that many products claiming sexual enhancement are likely contaminated with dangerous hidden ingredients, and that its notification list covers only a small fraction of them.9
Adulterated study batch
In a 2010 study, the Butea batch that matched sildenafil was most likely blended with a PDE5 inhibitor, as its supplier later confirmed; a second batch showed no effect.2
Raised androgen levels
A man using locally made Butea capsules for hair loss had dihydrotestosterone of 1,512 pg/mL (reference 250 to 990), which returned to normal one week after stopping.3
Rat toxicology
High doses lowered testosterone and raised liver enzymes over 90 days, and 1,000 mg/kg/day increased micronuclei, a marker of chromosome damage, in rat blood cells.45

How to read the label

What to check on the Supplement Facts panel.

How to read the label

2 checks
Red vs white kwao krua

Red kwao krua (Butea superba) is a different plant from white kwao krua (Pueraria mirifica), a phytoestrogen herb.11

A dramatic effect is a warning sign

In the 2010 study, the batch that worked like sildenafil contained a sildenafil-type drug; FDA says this product category is often contaminated.29

Have the bottle? Photograph its Supplement Facts panel and see each line, butea superba (red kwao krua) included, beside the doses and forms the trials used in Label X-Ray.

Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

7 answers
Does Butea superba work for erectile dysfunction?

There is no reliable evidence. The only placebo trial lost all its placebo participants, and a later study found no effect once an adulterated batch was replaced.1211

Does it raise testosterone?

Testosterone did not change in the 2003 trial; one case report described raised dihydrotestosterone, and in rats high doses lowered testosterone.1134

Does Butea superba help hair loss?

No trial has tested it. The one published case of a man using Butea capsules for hair loss reported dihydrotestosterone of 1,512 pg/mL, above the reference range, which returned to normal a week after stopping.3

Can women take Butea superba?

There are no human safety data in women. In female rats it had androgenic (male-hormone-like) effects on the uterus.6

Is it safe?

Safety in people is unstudied. Products in this category may hide prescription drugs, and high doses caused hormone and liver-enzyme changes in rats.924

Is Butea superba the same as white kwao krua (Pueraria mirifica)?

No. Red kwao krua is Butea superba, sold for male potency; white kwao krua is Pueraria mirifica, a different plant used as a phytoestrogen herb.11

Why did one study find it as strong as sildenafil?

The batch used was most likely blended with a PDE5 inhibitor, the drug class that includes sildenafil, which the supplier later confirmed.2

Sources

11 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

11 sources
  1. 1Clinical trial of Butea superba, an alternative herbal treatment for erectile dysfunction.RCT Asian J Androl, 2003 · PMID 12937809
  2. 2The use of Butea superba (Roxb.) compared to sildenafil for treating erectile dysfunction.Open-label trial BJU Int, 2010 · PMID 19624593
  3. 3Hyperandrogenemia due to ingestion of Butea superba.Observational Indian J Endocrinol Metab, 2012 · PMID 22629537
  4. 4Androgen disruption and toxicity tests of Butea superba Roxb., a traditional herb used for treatment of erectile dysfunction, in male rats.Animal study Maturitas, 2008 · PMID 18554827
  5. 5The toxicology of Butea superba, Roxb.Animal study Southeast Asian J Trop Med Public Health, 2002 · PMID 12971499
  6. 6Androgenic activity of the Thai traditional male potency herb, Butea superba Roxb., in female rats.Animal study J Ethnopharmacol, 2009 · PMID 19010408
  7. 7Luteinizing hormone reduction by the male potency herb, Butea superba Roxb.Animal study Braz J Med Biol Res, 2010 · PMID 20721473
  8. 8Rise of herbal and traditional medicine in erectile dysfunction management.Review Curr Urol Rep, 2011 · PMID 21948222
  9. 9Sexual Enhancement and Energy Product NotificationsSafety communication US Food and Drug Administration, 2026 · fda.gov
  10. 10Public Notification: JACK’D Sexual Enhancement Liquid contains hidden drug ingredientSafety communication US Food and Drug Administration, 2022 · fda.gov
  11. 11Clinical trial of Butea superba, an alternative herbal treatment for erectile dysfunction (full text)RCT Asian Journal of Andrology, 2003 · asiaandro.com

What changed

Every dated change to this page: what changed, who made it and why.

Change log

2 entries
Dated changes to this page
DateChangeWho and why
who should avoid, FAQ, questions, relatedPregnancy note now covers breastfeeding (no human data; no LactMed entry). Replaced the FAQ item that repeated the page's own "What is" question with red vs white kwao krua, and added FAQ items on hair loss and use by women, page questions and a goal-hub link. PubMed search (all years) found no human trial since 2010 and no meta-analysis; no LiverTox, LactMed, NCCIH or MedlinePlus entry exists, so the interaction list (FDA hidden-drug and hormone cautions) is unchanged.Writer: Kymata Health EditorialTrigger: A–Z audit against docs/supplements/AUDIT-STANDARD.md
allInitial editorial evidence review (first draft). Every PMID checked against NCBI E-utilities esummary (titles and years taken from the record, none retracted) and the abstract read for each cited row. Studied doses are reported as research doses, not dosing advice.Writer: Kymata Health EditorialTrigger: new page

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