Ipriflavone

Also called 7-isopropoxyisoflavone, synthetic isoflavone, Ostivone, Osten.

Best grade C across 3 graded outcomes Other Last checked Oct 25, 2026

The short answer

From 10 sources

A 2020 meta-analysis of 11 trials (1,605 women) found a small lumbar-spine bone density gain, but a 474-woman trial (600 mg a day for 36 months) found none and recorded low lymphocyte counts in 13.2% of users. The evidence is conflicting and limited to postmenopausal women.

Every graded outcome on this page

3 rows · line = participants

Grade CLumbar spine bone mineral densityBone densityn 1,605
Grade CLymphocyte count (safety)Safety: lymphocytesn 474
No effectBone density, bone markers and vertebral fracturesBone densityn 474

Key facts

What it is: A synthetic isoflavone made from the soy isoflavone daidzein; a 1999 review describes it as having no intrinsic estrogenic activity³
Pooled bone-density result: Lumbar spine standardized mean difference 0.36 (95% CI 0.09 to 0.62) across 11 trials, 1,605 postmenopausal women¹
Long multicenter trial: 474 women, 200 mg three times a day for 36 months: no difference in spine, hip or forearm bone density, bone markers or new vertebral fractures²
Immune safety signal: Subclinical lymphocytopenia in 31 of 234 women (13.2%) on ipriflavone; 22 of 29 who developed it during treatment had recovered by 2 years²
Dose tested: 200 mg three times a day (600 mg a day) with calcium, for 2 to 3 years^2,4

What it is

Ipriflavone is a synthetic isoflavone made from daidzein and sold for bone health; the largest trial found no bone-density benefit.

How it works

Proposed

Described as an isoflavone that appears to enhance estrogen's effect without being estrogenic itself, and to inhibit bone resorption while supporting bone formation. These actions are proposed; a 474-woman randomized trial found no change in bone-resorption markers.^3,2

Forms

Form

The form on this page
Form	Elemental %	Absorption (human data)	GI tolerance	Studied for
Ipriflavone (7-isopropoxyisoflavone) tablets or capsules	Varies³Not applicable (a synthetic compound, not a mineral)	In humans it is rapidly absorbed and quickly metabolized; about 57% of a dose is excreted in urine as metabolites and about 40% in feces, mostly as unchanged ipriflavone. In blood it is 94 to 99% bound to albumin.⁸	In 60 studies (2,769 patients) adverse reactions were 14.5% vs 16.1% on placebo, mainly gastrointestinal; the 4-year trial found lymphocytopenia in 13.2%.^4,2	Postmenopausal bone loss

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

3 graded outcomes, largest study first

3 graded outcomes: 1 improved, 1 no effect, 1 worsened. The largest, a 2020 meta-analysis of 1,605 people on lumbar spine bone mineral density, found an improvement. One outcome found a worsening: lymphocyte count (safety) (474 people).

By ageBy sizeTable

AgeAll ages

Bar: the ages a study enrolled (running to the edge when it states no upper or lower limit). Dot: only a mean age, counted as near your age within 5 years. Tick: the mean age inside a range.

2Lymphocyte count (safety): worsened, 45–75

3Bone density, bone markers and vertebral fractures: no effect, 45–75

1Lumbar spine bone mineral density: improved, ages not stated

1Lumbar spine bone mineral density

Improved · Grade C · Meta-analysis, 1,605 people, 2020

Postmenopausal women with osteopenia or osteoporosis

Dose, result and source

Every graded outcome on this page, largest study first
Outcome	Found	People	Study	Who was studied
Lumbar spine bone mineral density	Improved	1,605	Grade C · Meta-analysis, 2020	Postmenopausal women with osteopenia or osteoporosis
Lymphocyte count (safety)	Worsened	474	Grade C · RCT, 2001	Postmenopausal white women aged 45 to 75 with low bone density
Bone density, bone markers and vertebral fractures	No effect	474	No-effect grade · RCT, 2001	Postmenopausal white women aged 45 to 75 with low bone density

Every graded row

3 rows

Grade CLumbar spine bone mineral densityBone densitySmall spine gainMeta-analysis · 11 studies
n 1,605 · 2020

Improved Lumbar spine bone density rose more with ipriflavone than placebo (standardized mean difference 0.36, 95% CI 0.09 to 0.62); bone-resorption markers fell. Withdrawals due to adverse reactions were similar to placebo; stomach and gut symptoms were the most common reactions.

Design: Meta-analysis, 11 studies, n = 1,605, 2020
Population: Postmenopausal women with osteopenia or osteoporosis
Form: Ipriflavone (regimens varied by trial)
Dose: Doses not stated in the abstract
Duration: Varied by trial
Source: Reference 1 · PubMed 32407952 (opens PubMed)

Grade CLymphocyte count (safety)Safety: lymphocytesLower lymphocyte countsRCT
n 474 · 2001

Worsened Lymphocyte concentrations fell by about 500 per microliter; 31 women (13.2%) on ipriflavone developed subclinical lymphocytopenia. Of 29 who developed it during treatment, 15 (52%) had recovered by 1 year and 22 (81%) by 2 years.

Design: RCT, n = 474, 2001
Population: Postmenopausal white women aged 45 to 75 with low bone density
Form: Ipriflavone tablets
Dose: 200 mg three times a day (600 mg a day)
Duration: Up to 36 months analysed
Source: Reference 2 · PubMed 11255425 (opens PubMed)

No effectBone density, bone markers and vertebral fracturesBone densityNo bone-density benefitRCT
n 474 · 2001

No effect Annual change in lumbar spine bone density did not differ from placebo (0.1% vs 0.8%, P = .14), nor did hip, forearm, bone markers or new vertebral fractures.

Design: RCT, n = 474, 2001
Population: Postmenopausal white women aged 45 to 75 with low bone density
Form: Ipriflavone tablets
Dose: 200 mg three times a day (600 mg a day), all with 500 mg calcium a day
Duration: 36 months analysed (4-year study)
Source: Reference 2 · PubMed 11255425 (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.

A 474-woman trial is null; the pooled result is positive

The 474-woman trial found no bone-density difference at 36 months, while a pool of 11 trials (1,605 women) found a small spine gain, so the answer depends on which evidence you weigh.^2,1

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 600 mg a day (200 mg three times a day, the regimen in the trials cited here) for 2 to 3 years; other regimens pooled in the 2020 meta-analysis are not stated in its abstract.^2,4,1

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 Ipriflavone meets

2 cited rows

Medicines 2

Ipriflavone2 medicines · 0 supplements

Supplements and foods 0

No supplement rows in our sources.

Measured in a human study
Case reports

Interactions

2 agents

Published interactions, grouped by kind
Agent	What the source says	Evidence
Medicines2
Theophyllinee.g. Theophylline for asthma or COPD	Serum theophylline rose in a patient with COPD during ipriflavone use and fell after ipriflavone was stopped. In human liver microsomes, ipriflavone and its metabolites blocked theophylline's main breakdown pathway, so the interaction is plausible.^7,5,6	Case report
Drugs cleared by the same liver enzymese.g. Tolbutamide; substrates of phenacetin O-deethylase (CYP1A2)	In human liver microsomes ipriflavone and its 7-hydroxy metabolite competitively inhibited phenacetin O-deethylase and tolbutamide hydroxylase activity (Ki about 10 to 20 micromolar). Patients on 600 mg a day had steady-state blood levels of 0.33 and 1.44 micromolar for the two compounds. Other drugs were not tested.⁵	PK study

Check with what you take

Kept on this device only

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

Add a supplement or medicine

Most cited:

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

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.

Who should be careful

4 groups

Low lymphocyte counts or immune suppression: Ipriflavone lowered lymphocyte counts in the 474-woman trial. No study tested it with immune-suppressing medicines or in people with existing low counts; avoiding that combination is an inference from the lymphocyte finding.²
Kidney disease: In patients with renal failure, steady-state blood levels of ipriflavone and its metabolites were higher than in healthy volunteers, and renal elimination fell as kidney disease worsened.⁹
People on theophylline: Serum theophylline rose during ipriflavone use in a reported case; see the interactions table.^7,6
Men, pregnancy and breastfeeding: The trials cited here enrolled postmenopausal women; none of the cited abstracts studied men, pregnancy or breastfeeding.^1,2

How to read the label

What to check on the Supplement Facts panel.

How to read the label

2 checks

Label dose vs studied dose

The trials used 200 mg three times a day (600 mg a day) alongside 500 mg to 1 g of calcium a day. Add up the label's daily total across servings and compare it with 600 mg; a smaller amount was not what these trials tested.^2,4

Regulatory status

The 2020 meta-analysis authors describe ipriflavone as an over-the-counter drug for osteoporosis in more than 22 countries since 1989. None of the sources cited here reports an FDA approval; the FDA does not approve dietary supplements for safety or effectiveness before sale, and a product marketed with disease claims is regulated as a drug.^1,10

Label X-RayPhotograph a bottle's Supplement Facts panel and see each line, ipriflavone included, beside the doses and forms the trials used

Frequently asked questions

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

Common questions

5 answers

Does ipriflavone build bone?

Results conflict. A 2020 pooled analysis of 11 trials found a small lumbar-spine gain, but a 474-woman, 36-month trial found no bone-density change.^1,2

Does ipriflavone lower fracture risk?

In the 474-woman trial the number of women with new vertebral fractures was identical or nearly so in both groups at every time point.²

Is ipriflavone safe?

In 60 studies adverse reactions were similar to placebo (14.5% vs 16.1%), mostly gastrointestinal, but a 4-year trial found low lymphocyte counts in 13.2% of users.^4,2

Does ipriflavone interact with medicines?

It raised serum theophylline in a reported COPD patient, and lab work shows it inhibits liver enzymes that handle theophylline and tolbutamide.^7,5

What dose was studied?

200 mg three times a day (600 mg a day) with calcium, for 2 to 3 years. That is the research regimen, not a recommendation.^2,4

Sources

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

Sources cited on this page

10 sources

1The efficacy and safety of ipriflavone in postmenopausal women with osteopenia or osteoporosis: A systematic review and meta-analysis.Meta-analysis Pharmacol Res, 2020 · PMID 32407952
2Ipriflavone in the treatment of postmenopausal osteoporosis: a randomized controlled trial.RCT JAMA, 2001 · PMID 11255425
3Ipriflavone: an important bone-building isoflavone.Review Altern Med Rev, 1999 · PMID 9988779
4Efficacy of ipriflavone in established osteoporosis and long-term safety.Review Calcif Tissue Int, 1997 · PMID 9263613
5Ipriflavone as an inhibitor of human cytochrome P450 enzymes.PK study Br J Pharmacol, 1998 · PMID 9517377
6The effect of ipriflavone and its main metabolites on theophylline biotransformation.PK study Eur J Drug Metab Pharmacokinet, 1996 · PMID 8839679
7Elevation of serum theophylline levels by ipriflavone in a patient with chronic obstructive pulmonary disease.Observational Eur J Clin Pharmacol, 1992 · PMID 1425881
8[Pharmacokinetics of ipriflavone].Review Acta Pharm Hung, 1995 · PMID 8742629
9Steady-state pharmacokinetics of ipriflavone and its metabolites in patients with renal failure.PK study Int J Clin Pharmacol Res, 1991 · PMID 1813437
10FDA 101: Dietary SupplementsFact sheet U.S. Food and Drug Administration, 2022 · fda.gov

What changed

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

Change log

2 entries

Dated changes to this page
Date	Change	Who and why
Oct 25, 2026evidence	Adversarial review: rows, key facts, interactions and safety notes re-read against the abstracts (numbers match). The "no intrinsic estrogenic activity" key fact is now attributed to the 1999 review it comes from rather than stated as established.	Writer: Kymata Health EditorialTrigger: adversarial review
Oct 17, 2026all	Initial editorial evidence review. Every PMID checked against NCBI E-utilities esummary (title, year, journal) and each cited abstract read; numbers taken from the abstracts only. The 2001 JAMA RCT and 2020 meta-analysis are shown side by side because they disagree. Funding is not stated in the abstracts.	Writer: Kymata Health EditorialTrigger: new page

Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.

Ipriflavone

Medicines 2

Supplements and foods 0

Drugs cleared by the same liver enzymes

Theophylline