Prostate Power Rx has several key Ingredients for support of normal prostate size and is carefully formulated with important herbs and nutrients to provide optimal prostate health.
Saw Palmetto extract standardized to contain 45% fatty acids - serenoa repens fruit
Stinging-Nettle 4:1 extract (urtica diocia root)
Quercetin
Rosemary 4:1 extract
Beta Sitosterol
Pygeum afrcianum extract
Daidzein, Genistein, and Lycopene.

Q. I am a researcher in Australia. I note that quercetin interacts with finasteride, which may affect that product's effect in reducing hair loss: "Finasteride alone caused a significant decrease in serum DHT level and prostate weight. Co-administration of quercetin with finasteride prevented the finasteride-induced decrease in serum DHT levels." My question is; in your opinion, will this impact on the benefit of finasteride's reduction in hair loss by reducing serum DHT?
  A.  I have a summary of the study below. The amount of quercetin given the rats per body weight is much higher than what a person would normally ingest. I think rodent studies are helpful but I do not rely on them much since over the years I have seen very different or even completely opposite results in humans. The 100 mg per kg of body weight given to a rat would be about 7000 mg in humans. Even if 3 capsules of quercetin are taken, this would amount to 1000 mg, seven times less than in the rodent. This could make a significant difference. Add to this the different hormonal status in humans compared to rodents, different diets, sleep patterns, liver metabolism, etc. All this gives too many variables to make heads or tails (excuse the pun) from the results of this study. If I interpret the results of this study further, you can see that the different dosage of quercetin led to different levels of DHT, one dose let to a 125% increase, while another dosage led to a decrease to 73 percent of the control.

Reduction of rat prostate weight by combined quercetin - finasteride treatment is associated with cell cycle deregulation.
J Endocrinol. 2004.
Benign prostate hyperplasia and prostate cancer are major public health problems. We report herein that daily treatment of male rats with 50, 100 or 150 mg quercetin per kg body weight. Concomitantly, serum testosterone levels were increased by 1.79-, 1.83- and 3.48-fold, while serum dihydrotestosterone (DHT) levels were 125%, 92% and 73% of the control. A slight increase in prostate weight coupled with dilated prostate lumens full of secretory materials were observed. Finasteride alone caused a significant decrease in serum DHT level and prostate weight. Co-administration of quercetin with finasteride prevented the finasteride-induced decrease in serum DHT levels but significantly enhanced the reduction in wet prostate weight, which was reduced by 26.9% in finasteride-treated animals to 31.8%, 40.0% and 48.2% after finasteride given together with the three doses of quercetin. The combined treatment altered cell cycle-regulated proteins in a wide spectrum. In conclusion, quercetin - finasteride treatments caused wide cell cycle deregulation in rat prostates, which, in turn, decreased the proliferation rate, changed the secretion activities of epithelial cells and resulted in a marked reduction in wet prostate weight. The results suggest that quercetin synergizes with finasteride to reduce the wet prostate weight through a cell cycle-related pathway, which may be androgen independent.

Kidney disease
Quercetin reduces damage to kidneys in rats given a toxin or a chemotherapy drug such as cisplatin.

Protective Effect of Quercetin on the Evolution of Cisplatin-Induced Acute Tubular Necrosis.
Kidney Blood Press Res. 2004.
The bioflavonoid quercetin may be a potential alternative to reduce cisplatin-induced nephrotoxicity.

Drug Chem Toxicol. 2004. Quercetin, a bioflavonoid, attenuates ferric nitrilotriacetate-induced oxidative renal injury in rats.

Liver health
The liver of rats given toxins was much better protected when they were pre-treated with quercetin.

Phytomedicine. 2004. Studies on the protective effects of caffeic acid and quercetin on chemical-induced hepatotoxicity in rodents. Our results indicate that caffeic acid and quercetin exhibited hepatoprotective activity possibly through multiple mechanisms.

Prostatitis
I was made aware of this study by Dr. David C. Leopold, MD  who is at Scripps Center for Integrative Medicine in La Jolla, California.

Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial.
Urology. 1999. Shoskes DA, Zeitlin SI, Shahed A. Institute for Male Urology, Encino, California, USA.
The National Institutes of Health (NIH) category III chronic prostatitis syndromes (nonbacterial chronic prostatitis and prostatodynia) are common disorders with few effective therapies. Thirty men with category IIIa and IIIb chronic pelvic pain syndrome were randomized in a double-blind fashion to receive either placebo or the bioflavonoid quercetin 500 mg twice daily for 1 month. The NIH chronic prostatitis symptom score was used to grade symptoms and the quality-of-life impact at the start and conclusion of the study. In a follow-up unblind, open-label study, 17 additional men received 1 month of a supplement containing quercetin, as well as bromelain and papain (Prosta-O), which enhance bioflavonoid absorption. Patients taking placebo had a mean improvement in NIH symptom score from 20 to 18 (not significant), while those taking the bioflavonoid had a mean improvement from 21 to 13. Twenty percent of patients taking placebo and 67% of patients taking the bioflavonoid had an improvement of symptoms of at least 25%. In the 17 patients who received Prosta-Q in the open-label study, 82% had at least a 25% improvement in symptom score. Therapy with the bioflavonoid quercetin is well tolerated and provides significant symptomatic improvement in most men with chronic pelvic pain syndrome.

Is quercetin effective for prostatitis?
   One study shows it helps prostatitis, a prostate infection or inflammation. Quercetin has potential as one nutrient out of many to be helpful in prostate enlargement. The dose of quercetin used in the prostatitis study was 500 mg twice daily. We will need a few more studies regarding the role of quercetin in the treatment of prostatitis to have a clearer idea of the benefits of this supplement for this condition.

Schizophrenia and brain tissue
Quercetin has potential for the treatment of neuroleptic-induced extrapyramidal side effects, such as from the drug haloperidol. Quercetin is a powerful antioxidant that may protect brain cells from damage.

Quercetin, a bioflavonoid, reverses haloperidol-induced catalepsy.
Methods Find Exp Clin Pharmacol. 2004.
Neuroleptics are extensively used in the treatment of schizophrenia and other affective disorders. Unfortunately their use is often associated with distressing side effects involving the extrapyramidal tract, such as Parkinsonism and tardive dyskinesia. Neuroleptic-induced catalepsy has long been used as a model for extrapyramidal side effects such as Parkinsonian-like bradykinesia associated with antipsychotic use in humans. In the present study, haloperidol was administered to mice to induce catalepsy. Pretreatment with quercetin dose-dependently reduced the catalepsy score in haloperidol-treated animals. The findings of the present study strongly suggest that quercetin can be screened as a potential drug candidate or as an adjuvant for the treatment of neuroleptic-induced extrapyramidal side effects.

Skin health and radiation damage
Radiat Res. 2013. Quercetin inhibits radiation-induced skin fibrosis in mice.

Statin drug use
In an article from 2011, 'Quercetin is a potential rationale therapeutic choice in order to treat statin myotoxicity' Joffrey Zoll, PhD, Jamal Bouitbir, Anne-Laure Charles, Bernard geny say, "We fully believe that quercetin or more largely some efficient natural antioxidant molecules targeting mitochondria should be beneficial for patients with statin-induced myalgias or myopathy."

Chronic ingestion of high doses of quercetin will decrease the bioavailability of simvastatin to a significant extent. Eur J Pharm Sci. 2009. Effects of the flavonol quercetin on the bioavailability of simvastatin in pigs.

Tylenol toxicity
Pathophysiology. 2014. Quercetin protects against acetaminophen-induced hepatorenal toxicity by reducing reactive oxygen and nitrogen species. Results suggest that the protective role of quercetin in the prevention of APAP-induced hepatorenal toxicity in rats was associated with the decrease of oxidative and nitrosative stress in hepatic and renal tissues as well as its capacity to improve the mitochondrial energy production. However, clinical studies are warranted to investigate such an effect in human subjects.

Quercetin side effects, is the supplement safe?
At this time quercetin side effects have been reported in the medical literature. I have personally taken 3 capsules of quercetin and bromelain for 3 days in a row without side effects. Adverse reacations with long term supplementation over several years is not known. Thyroid function could be influenced.

Food Chem Toxicol. 2014. The flavonoid quercetin inhibits thyroid-restricted genes expression and thyroid function. Quercetin is the most abundant flavonoid present in a broad range of fruit and vegetables. Furthermore, quercetin is available as dietary supplements that are based on its antioxidant, antiproliferative and anti-inflammatory properties. However, concerns have been raised about the potential toxic effects of excessive intake, and several studies have demonstrated that flavonoids can interfere with thyroid function. In a previous report, we showed that quercetin inhibits thyroid-cell growth and iodide uptake. The latter effect was associated with down-regulation of sodium/iodide symporter gene expression. In the present study, we have evaluated the effects of quercetin on the expression of other thyroid-restricted genes, and we show that quercetin decreases the expression of the thyrotropin receptor, thyroid peroxidase and thyroglobulin genes. We further investigated the inhibitory effects of quercetin on thyroid function in vivo through evaluation of radioiodine uptake in the Sprague-Dawley rat, which was significantly decreased after 14days of quercetin treatment. These data confirm that quercetin can act as a thyroid disruptor, and they suggest that caution is needed in its supplemental and therapeutic use.

Absorption
Quercetin is readily absorbed from the intestinal tract and blood levels rise as the dosage of the quercetin supplement increases. Quercetin is commonly present as a glycoside and is converted to glucuronide / sulfate conjugates during intestinal absorption and conjugated metabolites are found in circulating blood.

Quercetin and drug, medication interactions
Quercetin influences activities of several drug metabolizing enzymes including CYP1A2, CYP2A6, NAT2 and XO.

Short-term effect of quercetin on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein, in healthy volunteers.
Eur J Clin Pharmacol. 2009. Department of Clinical Pharmacology and Toxicology, Anam Hospital, Korea University College of Medicine, Sungbuk-gu, Seoul, Korea.
The aim of the present study was to assess whether quercetin exhibited any inhibitory effect on P-glycoprotein (P-gp)-mediated drug disposition in humans using fexofenadine as a P-gp substrate. Twelve healthy subjects were enrolled in the study and treated daily for 7 days with 500 mg quercetin or placebo 3 times a day. On day 7, a single dose of 60 mg fexofenadine was administered orally. Plasma and urinary fexofenadine concentrations were measured, and pharmacokinetic differences between placebo and quercetin phases were assessed. The mean plasma concentrations of fexofenadine were significantly increased after quercetin treatment compared to those of the placebo phase. The results of the present study showed that short-term use of quercetin elevated the plasma concentrations of fexofenadine, probably by the inhibition of P-gp-mediated efflux in humans.

Q. Can you comment on the interaction of quercetin and clopidogrel? Am I correct in understanding that it significantly increases the platelet inhibition of clopidogrel.

Arch Pharm Res. 2012. Pharmacokinetic interactions of clopidogrel with quercetin, telmisartan, and cyclosporine A in rats and dogs. Following the oral administration of clopidogrel with or without the P-gp inhibitors, quercetin (250 mg/kg), telmisartan (8 mg/kg), and cyclosporine A (10 mg/kg), in rats and dogs, the plasma concentration-time profiles of clopidogrel carboxylic acid, a surrogate marker for the bioavailability of clopidogrel, were determined. Co-administration of the quercetin, telmisartan and cyclosporine A significantly increased the area under the curve and peak plasma concentration of clopidogrel carboxylic acid in rats. However, in dogs, the plasma concentrations of clopidogrel carboxylic acid were not considerably changed by the coadministration of three different kinds of P-gp inhibitors. These findings suggest potential interaction of clopidogrel with quercetin, telmisartan, and cyclosporine A, although there are differences between animal models.

Food content of flavonoids
The average U.S. adult eating a normal, healthy diet consumes about 25 to 50 milligrams of quercetin a day. Studies were conducted on the flavonoids (myricetin, quercetin, kaempferol, luteolin, and apigenin) contents of 62 edible tropical plants. The highest total flavonoids content was in onion leaves (1497 mg/kg quercetin, 391 mg/kg luteolin, and 832 mg/kg kaempferol), followed by Semambu leaves (2041 mg/kg), bird chili (1663 mg/kg), black tea (1491 mg/kg), papaya shoots (1264 mg/kg), and guava (1128 mg/kg). The major flavonoid in these plant extracts is quercetin, followed by myricetin and kaempferol. Luteolin could be detected only in broccoli (74 mg/kg dry weight), green chili (33 mg/kg), bird chili (1035 mg/kg), onion leaves (391 mg/kg), carrot (37 mg/kg), white radish (9 mg/kg), local celery (80 mg/kg) and dried asam gelugur (107 mg/kg). Apigenin was found only in Chinese cabbage (187 mg/kg), bell pepper (272 mg/kg), garlic (217 mg/kg), French peas (176 mg/kg), snake gourd (42 mg/kg), guava (579 mg/kg), wolfberry leaves (547 mg/kg), local celery (338 mg/kg), and kadok (34 mg/kg). In vegetables, quercetin glycosides predominate, but glycosides of kaempferol, luteolin, and apigenin are also present. Fruits contain almost exclusively quercetin glycosides, whereas kaempferol and myricetin glycosides are found only in trace quantities.

Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003.

Content of the flavonols quercetin, myricetin, and kaempferol in 25 edible berries.
J Agric Food Chem. 1999.
Sixteen species of cultivated berries and nine species of wild berries were collected in Finland. Quercetin was found in all berries, the contents being highest in bog whortleberry (158 mg/kg, fresh weight), lingonberry (74 and 146 mg/kg), cranberry (83 and 121 mg/kg), chokeberry (89 mg/kg), sweet rowan (85 mg/kg), rowanberry (63 mg/kg), sea buckthorn berry (62 mg/kg), and crowberry (53 and 56 mg/kg). Amounts between 14 and 142 mg/kg of myricetin were detected in cranberry, black currant, crowberry, bog whortleberry, blueberries, and bilberry. Kaempferol was detected only in gooseberries (16 and 19 mg/kg) and strawberries (5 and 8 mg/kg). Total contents of these flavonols (100-263 mg/kg) in cranberry, bog whortleberry, lingonberry, black currant, and crowberry were higher than those in the commonly consumed fruits or vegetables, except for onion, kale, and broccoli.

Testimonial
I came across your website after doing a search dot 'quercertin sleepy'. I couldn't see anything further though in the side effects heading but I just wanted to raise the point that after using this supplement with food, I always had a drowsy effect which would conk me out for a couple hours at least. I do have a questionable thyroid function though.

Quercetin research studies
An apple a day really does keep the doctor away, thanks to strong antioxidants that fight cell damage. Rat brain cells exposed to the antioxidant quercetin resisted damage much better than those not treated, a team at Cornell University in New York found. The researchers say their study adds strength to the theory that the risk of developing Alzheimer's and similar brain diseases might be reduced by eating plenty of fresh fruits and vegetables. Writing in the December 1st issue of the Journal of Agricultural and Food Chemistry, the Cornell team said they soaked rat brain cells in either quercetin or vitamin C -- another potent antioxidant. The cells were then exposed to hydrogen peroxide to mimic the type of oxidative cell damage that is believed to occur with Alzheimer's disease. Brain cells that were treated with quercetin had significantly less damage than the cells treated with vitamin C and cells that were not treated with antioxidants.

Plant compounds may curb cancer growth
Several studies have shown that a group of antioxidant compounds found in grapes, green tea, soybeans and wine may lower the risk of a range of cancers, but exactly how these powerful compounds work has remained unclear. Now, researchers report that a plant-derived polyphenol can slow the growth of pancreatic cancer cells in mice and curb the spread of cells by triggering a series or reactions that causes the cells to self-destruct, a process known as apoptosis. In the study, the researchers investigated the effects of quercetin -- a type of antioxidant polyphenol commonly found in apples -- in mice given injections of human pancreatic cells. The mice used in the study are a specially bred strain that lacks an immune system, so that they quickly grow tumors when cancer cells are injected. Quercetin caused apoptosis, decreased the growth of the main tumor and inhibited the spread of malignant cells, the researchers report. Mice treated with quercetin survived for about 75 days, compared with 67 days in mice not given the compound. Genistein, another type of polyphenol compound found in soy, also prevented the spread of cells and inhibited the growth of the primary tumor in mice while resveratrol, found in wine and grapes, caused apoptosis in laboratory-grown cells, according to the report. International Journal of Cancer 2002:98;761-769.

Emails
Q. What is the difference between quercetin and quercetin chalcone?
   A. I don't know for sure. Chalcones are also intermediates in the biosynthesis of flavonoids, and quercetin chalcone may just be a form slightly different biochemically.

Q. As one professional to another, I would appreciate your clinical advice. Some studies indicate quercetin can exert a net pro-inflammatory response (albeit at high doses in combination with other bioflavinoids). Some researchers have claimed quercetin might cause inflammatory responses involving the PIP, MIP and Dip joints of the hands and feet; some claim an altered uric acid metabolism. Have you any experience in this regard? I have started quercetin at 250 mg bid (along with saw palmetto, zinc/copper and nettle leaf) to balance my DHT-T-E ratio and have experienced a new onset of said joint effects.
   A. I have not come across any studies and do not have any personal feedback from quercetin users regarding the association between quercetin and joint pain.

Q. I have been taking a formula which contains 250 MG of quercetin. I have been taking 4 pills a day. It works great for allergies but I recently found out I am pregnant. I came across some warnings of birth defects. Of course I am very upset and hoping you might have some access to studies or info regarding the use of quercetin during conception. I am only 5 weeks pregnant.
   A. I have not seen any human studies regarding the use of quercetin supplements during pregnancy. I found this rodent study which appears to be reassuring regarding implantation. The human dosage often taken is about 10 to 20 mg quercetin per kilo. Your doctor needs to make the final decision regarding continuing or stopping the quercetin.

Q. Let me again thank you for the great work you do. Whenever I encounter new research or information on a supplement, my first stop is your website, which I think is balanced and trustworthy. I was especially interested in the research on quercetin and upper respiratory tract infections. This past year I started to get serious about fitness and have a routine that is quite intense. Although it's helped me look and feel great (and took my blood pressure from borderline high to perfect), I had a winter filled with colds and other sinus problems, which I attribute in hindsight to overdoing it on exercise. Although I've slowed down a little, I don't want to stop being at a top fitness level. Thus, I'm quite interested in the study about quercetin and colds. My question is this: do you believe there would be an ideal time (e.g. before, during, or after workouts) to take the quercetin supplement to get the most antiviral benefit on days of intense training?
   A. I have not seen studies evaluating the timing of quercetin supplement intake and relationship to viruses and colds. I don't think timing is a major influence but I could be wrong. The proper use of vitamin C and zinc lozenges could reduce the frequency or severity of a cold. Deep sleep is utmost importance in maintaining a healthy immune system. 

I just read on your website about quercetin products. About 3 weeks ago I broke out in hives all over my body. I have been on 24hr antihistamines every since. There were only two things that I can think of that changed in my routine / diet. The first was that I took a Greens plus Tropical flavoured smoothie one morning and the other being I started to take quercetin capsules 500mg. I had taken 1 tablet each day for two days before I first noticed the histamine reaction. Since I had taken the Greens+ regular flavoured smoothie regularly for months with no issues, I figured the reaction would more likely be to the quercetin. I have not take either since the reaction began. I have read a little about the possibility of being allergic to quercetin. Are you familiar with this? The product is AOR Clasic Series, Quercetin 3,3',4',5,7-Pentahydroxyflavone, contains 500mg of quercetin capsule - hypromellose, sorbitol, silicon dioxide, water.
    This is the first time we have had an email regarding a possible allergic reaction to quercetin products.

I read that quercetin can be helpful for people with interstitial cystitis. I want to try it but read about interactions between quercetin and Estrace. I take 1 mg. estrace daily. Is there any problem with taking the estrace with 1500 mg. of quercetin daily?
    I have not seen studies regarding the interaction of this nutrient and estradiol.

I am currently taking one tablet of 500mg of quercetin supplement daily for about 9 months per year for the last two years. I would like to know about possible side effects of such an intake for a prolonged period of time. Since I am a marathon runner, I would also be interested in possible benefits in the athletic sector of this dosage or any other dosage that would be safe. Moreover, is it meaningful to search for the pros and cons of synthetic quercetin capsules versus natural, or is everything relatively safe?
   No long term studies have been done with daily use, but it seems to be safe. Nevertheless it is a good idea to take breaks once in a while since we don't know everything yet about its long term use. If the actual chemical is quercetin in the capsule, it does not matter what the source is.

Dietary supplements over the counter
There are a number of nutritional supplement companies that sell Quercetin, some by itself, others combined with bromelain, vitamin C, or other nutrients.

Quercetin 500 mg per 2 capsules (Dimorphandra mollis) (fruit). It is not clear from the supplement fact panel of this product whether it has 500 mg of quercetin per two capsules or whether it has 500 mg of the fruit with some of it being quercetin.
500 mg, 120 capsules
500 mg 60 tablets.

Activated Quercetin and Bromelain by Source Naturals
Activated quercetin with bromelain is a unique bioflavonoid derived product from plant sources. In human cell culture studies, it has been shown to inhibit histamine release. Additional research needs to be conducted to increase our awareness of the benefits in humans. Bromelain is a pineapple enzyme.

Supplement facts:
Vitamin C (as magnesium ascorbate)
Magnesium (as magnesium ascorbate)
Quercetin 1 gram per 3 capsules, is a potent antioxidant
Bromelain

MRM Quercetin 500 mg each pill
Buy Quercetin 500 mg

Other products to buy online
Now Foods, Quercetin with Bromelain, 240 Veg Capsules
Solaray, Quercetin, 500 mg, 90 VegCaps

Buy Quercetin
Activated quercetin with bromelain is a unique bioflavonoid derived product from plant sources. In human cell culture studies, it has been shown to inhibit histamine release. Additional research needs to be conducted to increase our awareness of the benefits in humans. Bromelain is a pineapple enzyme.