Name: Limbrel



OA as a Metabolic Deficiency Disease

Metabolic processes are important in the progression of OA. After initial damage to the joint due to trauma, overuse, or genetic factors, a cascade of inflammation, triggered by the release of cytokines (e.g., TNFα, IL-β, IL-6), begins the development of OA. These cytokines up-regulate the expression of COX-2 (cyclooxygenase-2) and 5-LOX (5-lipoxygenase) enzymes, which metabolize fatty acids in the joint. This process is both enzymatic as well as oxidative, and occurs at a cellular level where the essential fatty acid, arachidonic acid (AA), is converted into various inflammatory products. With age, elevated levels of AA accumulate both from the diet and increased conversion of phospholipids produced by further damage to cells in the joint. Therefore, OA is sustained by imbalanced AA metabolism. Managing AA metabolism benefits OA patients by decreasing the damaging, metabolic inflammatory processes in the joint to improve functional mobility, reduce stiffness, and decrease joint discomfort.

When joint damage occurs, phospholipids released from damaged cell membranes are converted to AA. Enzymatic breakdown of AA then generates fatty acid metabolites that are involved in platelet aggregation, maintenance of stomach mucosa, organ function, proper blood flow, urine production, blood pressure, viral immunity, bone turnover and tissue repair. AA is metabolized via the COX (COX-1 & COX-2) and LOX (5-LOX) pathways to thromboxanes, prostaglandins, prostacyclins, and leukotrienes. Balanced AA metabolism by COX-1 and COX-2 is essential to sustain proper levels of critical regulators for renal and cardiovascular function maintained by thromboxanes (vasoconstrictors) and prostacyclins (vasodilators). An imbalance of these metabolites can result in high blood pressure, peripheral edema and, in severe cases, myocardial infarction. AA, metabolized by 5-LOX, produces leukotrienes (particularly LTB4), that are strong chemoattractant molecules responsible for the migration of white blood cells (WBCs) to the site of injury. WBCs attracted to the joint by leukotrienes release histamines, produce reactive oxygen species (ROS) and cytokines, triggering additional inflammatory processes not treated by traditional non-steroidal anti-inflammatory drugs (NSAIDs) or selective COX-2 inhibitors. Inhibition of either or both COX-1 and COX-2 has been shown to shunt AA metabolism down the 5-LOX pathway, thereby potentially increasing, rather than reducing, inflammation in cartilage. In addition, AA is converted via an oxidative mechanism mediated by reactive oxygen species (ROS) to the oxidized lipids F2-isoprostanes, malondialdehyde, and 4-hydroxynonenal that directly degrade cartilage and induce production of other inflammatory proteins.

Primary Ingredients

LIMBREL (flavocoxid) consists of a proprietary blend of two types of flavonoids, Free-B-Ring flavonoids and flavans, from Scutellaria baicalensis and Acacia catechu, respectively. These ingredients in LIMBREL (flavocoxid) are Generally Recognized As Safe (GRAS). For an ingredient to be recognized as GRAS, it requires technical demonstration of non-toxicity and safety, general recognition of safety through widespread usage, and agreement of that safety by experts in the field. Many ingredients have been determined by the U.S. Food and Drug Administration (FDA) to be GRAS, and are listed as such by regulation, in Volume 21 Code of Federal Regulations (CFR) Sections 182, 184, and 186. Other ingredients may achieve “self-affirmed” GRAS status via a panel of experts in the pertinent field who co-author a GRAS Report. Finally, the FDA has specifically permitted a few ingredients as safe medical foods ingredients in Volume 21 CFR Section 172.345(f).


Flavonoids are a group of phytochemical compounds found in all vascular plants, including fruits and vegetables. They are a part of a larger class of compounds known as polyphenols. Many of the therapeutic or health benefits of colored fruits and vegetables, red wine, and green tea are directly related to their flavonoid content.

The specially formulated flavonoids found in LIMBREL (flavocoxid) , or their related compounds (i.e., other flavonoids, anthocyanins), cannot be obtained from conventional foods in the normal American diet at the same level as found in LIMBREL (flavocoxid) . This quantity of daily flavonoid intake generally would need to be significantly greater for patients with hypochlorhydria or low intrinsic factor, both of which occur most often in the elderly population. OA may not be managed simply by a change to the normal diet due to the high volume of vegetable and fruit matter that would need to be consumed.


The primary Free-B-Ring flavonoid is baicalin (5,6,7-trihydroxyflavone,7-O-β-D-glucuronopyranoside), derived from the phytochemical food source material Scutellaria baicalensis, with a molecular weight of 446.37. Its molecular formula is C21H18O11, with the following chemical structure:

The primary flavan is composed of catechin (3,3',4',5,7-pentahydroxyflavan (2R,3S form)), and its stereo-isomer, epicatechin (3,3',4',5,7-pentahydroxyflavan (2R,3R form)) from the phytochemical food source material Acacia catechu with a molecular weight of 290.27. Its molecular formula is C15H14O6, with the following chemical structure:

Other Ingredients

LIMBREL (flavocoxid) contains the following “inactive” or other ingredients as fillers, excipients, and colorings: magnesium stearate, microcrystalline cellulose, Maltodextrin NF, gelatin (as the capsule material), titanium dioxide, FD&C Blue #1, and FD&C Green #3. Capsules do not contain fructose, glucose, sucrose, lactose, gluten or flavors.

Medical Foods

Medical food products are often used in hospitals (e.g., for burn victims or kidney dialysis patients) and outside of a hospital setting under a physician's care (e.g., for PKU, AIDS patients, cardiovascular disease, osteoporosis) for the dietary management of diseases in patients with particular medical or metabolic needs due to their disease or condition. Congress defined "medical food" in the Orphan Drug Act and Amendments of 1988 as "a food which is formulated to be consumed or administered enterally [or orally] under the supervision of a physician, and which is intended for the specific dietary management of a disease or condition for which distinctive nutritional requirements, based on recognized scientific principles, are established by medical evaluation.“ LIMBREL (flavocoxid) has been developed, manufactured, and labeled in accordance with both the statutory and the FDA regulatory definition of a medical food. LIMBREL (flavocoxid) is to be used under a physician's supervision.

Physical Description

LIMBREL (flavocoxid) is a yellow to light brown powder. It is partially soluble in water and glycerol, soluble in ethanol, methanol, and acetonitrile. It is practically insoluble in hexane. Each capsule of LIMBREL contains 250 mg or 500 mg of flavocoxid, as noted in the Primary Ingredients Section.


Recommended Use

LIMBREL (flavocoxid) is intended for the clinical dietary management of the metabolic processes of osteoarthritis (OA).

Disclaimed Use

LIMBREL (flavocoxid) has not been investigated for use in the clinical dietary management of rheumatoid arthritis (RA), acute pain or primary dysmenorrhea.


There are no known cases of LIMBREL (flavocoxid) over usage. Animal studies have shown that consuming the equivalent of at least 10 times the recommended human usage of 500 to 1,000 mg/day did not produce adverse events. However, as in most over usage situations, symptoms following an over usage of LIMBREL (flavocoxid) could vary according to the patient. If an over usage were to occur, patients should be managed by systematic and supportive care as soon as possible following product consumption.

Clinical pharmacology

Mechanism of Action

LIMBREL (flavocoxid) acts on COX-1, COX-2 and 5-LOX pathways. LIMBREL (flavocoxid) is NOT selective for either COX-1 or COX-2 enzymes. LIMBREL (flavocoxid) acts by restoring and maintaining the balance of fatty acids in OA. LIMBREL (flavocoxid) dampens AA metabolism at relatively equal levels in the COX pathway (mediated by conversion of AA via the COX-1 & COX-2 enzymes), as well as inhibiting the metabolism of AA by the 5-LOX enzyme. This balanced inhibition of metabolism in the COX pathway yields relatively equal levels of thromboxanes, prostaglandins, and prostacyclins that are key mediators of systemic organ function. Inhibition of these mediators in the COX pathway, in conjunction with inhibition of leukotrienes in the LOX pathway, results in a ”dual inhibition“ mechanism that manages inflammation with minimal effects on organ function. Inhibition of 5-LOX has been shown in cell-based assays to reduce the production of LTB4, an agent that fosters WBC chemotaxis and the subsequent release of histamines, ROS, and pro-inflammatory cytokines. In addition, direct inhibition of the 5-LOX enzyme has been observed in enzymatic assays. This balanced down-regulation of these enzymatic pathways is relatively weak when compared to the effects of traditional NSAIDs and selective COX-2 inhibitors, thus allowing the body to produce AA metabolites at relatively equal levels to maintain physiologic function.

LIMBREL (flavocoxid) also acts as a strong antioxidant to limit the oxidative conversion of AA by ROS to other damaging fatty acid products including hydroxyl radicals, superoxide anion radicals and hydrogen peroxide. LIMBREL (flavocoxid) has demonstrated an oxygen radical absorbance capacity (ORAC) of 5,517 μmolTE/g, as compared to Vitamin E (1,100 μmolTE/g) and Vitamin C (5,000 μmolTE/g).

Through these enzyme inhibition and antioxidant mechanisms, LIMBREL (flavocoxid) is beneficial for the clinical dietary management of the metabolic aspects of osteoarthritis. Inflammation, joint discomfort, and reduced flexibility are shown in published studies to be clinical manifestations of OA. At a biochemical and metabolic level, inflammation is not simply a marker of the disease process, but also plays an important role in OA progression. Chronic inflammation with elevated metabolic production of inflammatory metabolites has an etiological role in the progression of OA. Thus, successful dietary management of the metabolic processes ofOA, results in a reduction of its characteristic inflammation by correcting OA's distinctive imbalance in AA metabolism.

Hepatic, Renal, and Gastrointestinal Histology

LIMBREL (flavocoxid) 's effect on hepatic, renal, gastric, and duodenal tissue histology was tested in four animal toxicity studies; two for acute use and two for sub- chronic use.

In the acute use studies, healthy juvenile male and female mice received a 2,000 mg/kg oral dose (10,000 mg per day human equivalent, or at least 10 times the recommended human use of 500 - 1,000 mg per day) or placebo daily for 14 days. In two different sub-chronic use studies, three groups of healthy adult male and female mice consumed either 50 mg, 250 mg or 500 mg/kg doses (250 mg, 1,250 mg and 2,500 mg per day human equivalent) for 28 and 91 days respectively.

In all studies, the test subjects were evaluated relative to placebo control groups of healthy subjects with similar ages and sexes. Observations across all groups revealed no organ or behavioral abnormalities, nor differences in weight gain. Neither study showed changes in hepatic, renal, gastric, or duodenal histology. Blood electrolytes were unchanged, and liver enzyme levels and markers of renal function were all within normal limits.

Food Effects

LIMBREL (flavocoxid) is safe taken with or without other foods. Taking LIMBREL (flavocoxid) one hour before or after meals may help to increase the absorption of LIMBREL (flavocoxid) 's key ingredients. This observation is based upon a pharmacokinetic study in humans, as well as in-market clinical experience in analyzing physician and patient product reports. Food does not affect the metabolism of LIMBREL (flavocoxid) and may buffer effects of slight indigestion.


LIMBREL (flavocoxid) is primarily carried bound to albumin in the blood and only a minor amount ( < 10%) is metabolized via glucuronidation and sulfation by hepatic metabolism involving cytochrome P450 isoenzymes (CYP). A primary ingredient constituent, baicalin, undergoes hydrolysis of the glucuronide moiety in the upper intestine via the action of intestinal flora and is absorbed as the aglycone, baicalein. Glucuronidation and sulfation of baicalein occurs intra-hepatically. In vitro CYP assays using a microsomal enzyme system demonstrated minimal CYP inhibition (see below).

Drug Interactions

In vitro studies indicated that LIMBREL (flavocoxid) is not a significant inhibitor of cytochrome P450 1A2, 2C9, 2C19, 2D6, or 3A4. These isoenzymes are principally responsible for 95% of all detoxification of drugs, with CYP3A4 being responsible for detoxification of approximately 50% of drugs. Based on the results of this assay, LIMBREL (flavocoxid) does not appear to have a pronounced effect on drug metabolizing enzymes.

LIMBREL (flavocoxid) was tested at a 10 μM concentration in human recombinant (sf9 cells) using spectrophotometric quantization of 7-benzyloxy-4-(trifluoromethyl)-coumarin as substrate. In this test model, if inhibition does not reach at least 50% at 10 μM, CYP inhibition is considered to be insignificant and no further development of titration curves is deemed necessary. Inhibition by LIMBREL (flavocoxid) ranged from 11% inhibition to 23% inhibition of selected isozymes when studied at a 10 μM concentration.

LIMBREL (flavocoxid) , therefore, does not appear to have a pronounced effect on the inhibition of hepatic drug metabolizing enzymes based on this 10 μM concentration. The data for CYP inhibition is shown below:

Table 1. Cytochrome P450 Assay

CYP Isoenzyme % Inhibition by LIMBREL
1A2 23%
2C9 11%
2C19 16%
2D6 15%
3A4 11%

Clinical Experience

LIMBREL (flavocoxid) has demonstrated significant functional improvements when used for the clinical dietary management of the metabolic processes of OA.

Double-blind, Randomized Clinical Study vs. Naproxen

LIMBREL (flavocoxid) was evaluated in a double-blind, randomized, active comparator (naproxen) controlled clinical study that enrolled 103 subjects with moderate or moderate-severe OA of the knee. Subjects were randomly assigned to receive either LIMBREL (flavocoxid) (500 mg BID) or naproxen (500 mg BID) for 4 weeks. Primary endpoints were the short WOMAC composite index (Western Ontario and McMaster Universities Osteoarthritis Index), investigator VAS for global response, subject VAS scales for global response and discomfort. Subjects were sex-matched and recruited from ages 35 to 85 years with an average age of 57-60 years per arm. There were no differences in demographic characteristics or in baseline WOMAC or VAS scores between the two arms. Subjects taking NSAIDs and/or gastroprotective medication underwent a 2-week washout period before beginning the trial. Subject activity was not restricted, and subjects were free to withdraw from the trial at any time for any reason. Dropouts were minimal in both arms. Two subjects, one from each arm, failed to complete the trial for personal reasons unrelated to the study.

In thisstudy, both LIMBREL (flavocoxid) and naproxen arms noted significant reduction in the signs and symptoms of knee OA. All within-arm improvements in efficacy endpoints were statistically significant (p 0.001). The LIMBREL (flavocoxid) and naproxen arms performed nearly identically, and the between group differences were not statistically significant for any efficacy endpoint. See Figures 1-4 below for efficacy results of LIMBREL (flavocoxid) vs. naproxen in this study.

Figure 1. Improvement in WOMAC*

Figure 2. Improvement in Physician VAS (Global Disease Assessment)**

Figure 3. Improvement in Subject VAS (Global Disease Assessment)†

Figure 4. Improvement in Subject VAS (Discomfort Assessment) ††

Fisher's exact test was computed for improved vs. not improved (sum of unchanged and worsened) for all parameters (see Table 2). Both arms had a large percentage of subjects with significant improvement (75% to 88%). Differences were not significant between arms for percent of patients with improvement. There was a slight, non-significant trend toward greater improvement in physician global disease assessment VAS in the LIMBREL (flavocoxid) arm and WOMAC in the naproxen arm.

Table 2. Percent of OA Patients with Improvement

  LIMBREL (flavocoxid)
500 mg BID
500 mg BID
WOMAC 79% 88% < 0.001
Physician VAS (global disease assessment) 83% 75% < 0.001
Subject VAS (global disease assessment) 87% 88% < 0.001
Subject VAS (discomfort assessment) 87% 88% ≤ 0.001

Double-blind, Randomized Clinical Study vs. Placebo

LIMBREL (flavocoxid) was evaluated in a 90-day randomized, double blind, placebo-controlled clinical trial of 60 subjects. Subjects were sex-matched and recruited from ages 40 to 75 years with an average age of 55-57 years per arm. Subjects taking NSAIDs engaged in a two-week washout period before beginning the trial. Subject activity was not restricted, and subjects were free to withdraw from the trial at any time for any reason. Three subjects withdrew from the study for personal reasons unrelated to study procedures or products.

In patients with OA, use of LIMBREL (flavocoxid) at 125 mg and 250 mg BID resulted in significant improvements in WOMAC functional endpoints of stiffness and mobility over those scores of placebo users. In this study, patients using LIMBREL (flavocoxid) 250 mg twice daily experienced greater improvements in functional stiffness and functional mobility at 90 days than did patients using 125 mg twice daily. See Tables 3 and 4 below for a comparison of LIMBREL (flavocoxid) results to placebo for each noted measure.

Table 3. 90-day Functional Stiffness WOMAC Scores

  Mean % Change* p-value Conclusion
LIMBREL 250 mg/day -27.2% p=0.005 Significant improvement
LIMBREL 500 mg/day -38.0% p=0.002 Significant improvement
Placebo +3.1% p=0.324 No significant improvement
* Negative values indicated improvement in functional stiffness.

Table 4. 90-day Functional Mobility WOMAC Scores

  Mean % Change* p-value Conclusion
LIMBREL 250 mg/day +19.2% p=0.018 Significant improvement
LIMBREL 500 mg/day +28.4% p=0.001 Significant improvement
Placebo +2.3% p=0.895 No significant improvement
* Positive values indicated improvement in functional mobility.

Open Label Study

LIMBREL (flavocoxid) has been shown to be effective in an open label human trial with a mean duration of use of 6.5 months. This trial consisted of 24 subjects: 13 males and 11 females ranging from 26 to 60 years of age. The primary endpoints were WOMAC functional mobility (65% improvement; p=0.002) and functional stiffness (62% improvement; p=.001) scores before vs. after taking LIMBREL (flavocoxid) .

What is the most important information i should know about bioflavonoids?

Not all uses for bioflavonoids have been approved by the FDA. Bioflavonoids should not be used in place of medication prescribed for you by your doctor.

Bioflavonoids is often sold as an herbal supplement. There are no regulated manufacturing standards in place for many herbal compounds and some marketed supplements have been found to be contaminated with toxic metals or other drugs. Herbal/health supplements should be purchased from a reliable source to minimize the risk of contamination.

Use bioflavonoids as directed on the label, or as your healthcare provider has prescribed. Do not use this product in larger amounts or for longer than recommended.

What should I discuss with my healthcare provider before taking Limbrel (bioflavonoids)?

Do not use this product if you are allergic to bioflavonoids or if you have:

Before using bioflavonoids, talk to your doctor, pharmacist, herbalist, or other healthcare provider. You may not be able to use bioflavonoids if you have certain medical conditions.

Do not take bioflavonoids without first talking to your doctor if you are pregnant or planning a pregnancy. It is not known whether bioflavonoids will be harmful to an unborn baby.

Do not take bioflavonoids without first talking to your doctor if you are breast-feeding a baby. It is not known whether bioflavonoids will be harmful to a nursing infant.

Do not give any herbal/health supplement to a child without the advice of a doctor.

What should I avoid while taking Limbrel (bioflavonoids)?

There are no known restrictions on food, beverages, or activities while you are taking bioflavonoids unless otherwise directed by your health care provider.

What other drugs will affect Limbrel (bioflavonoids)?

There may be other drugs that can interact with bioflavonoids. Tell your healthcare provider about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your healthcare provider.

Commonly used brand name(s)

In the U.S.

  • Limbrel

Available Dosage Forms:

  • Capsule

Therapeutic Class: Nutriceutical

What are some things I need to know or do while I take Limbrel?

  • Tell all of your health care providers that you take Limbrel. This includes your doctors, nurses, pharmacists, and dentists.
  • This medicine is not approved for use in children younger than 18 years of age. Talk with the doctor.
  • Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using this medicine while you are pregnant.
  • Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.