Action and Spectrum

Actions and Spectrum: 

• Antioxidant activity: quercetin exhibits potent antioxidant properties, which can neutralize free radicals and reduce oxidative stress in the body. It acts as a scavenger of reactive oxygen species (ROS), helping to protect cells and tissues from oxidative damage. 
• Anti-inflammatory effects: quercetin possesses anti-inflammatory properties by inhibiting the production and release of inflammatory mediators, such as cytokines and prostaglandins. It can suppress the activity of enzymes involved in inflammation, such as cyclooxygenases (COX) and lipoxygenases (LOX). 
• Immunomodulatory effects: quercetin has been shown to modulate immune function by regulating immune cell activity and influencing cytokine production. It can enhance the activity of specific immune cells, such as natural killer (NK) cells, and exert a regulatory effect on the immune response. 
• Antiviral activity: quercetin has been studied for its potential antiviral effects against various viruses, including respiratory viruses such as influenza and coronaviruses. It can inhibit viral replication by interfering with various stages of the viral life cycle, including viral attachment, entry, and replication. 
• Anticancer effects: quercetin has been investigated for its potential anticancer properties. It can inhibit the growth and proliferation of cancer cells, induce apoptosis (programmed cell death), and prevent angiogenesis (formation of new blood vessels that supply tumors). quercetin may also exhibit chemopreventive effects by protecting against DNA damage and reducing oxidative stress. 
• Cardiovascular effects: quercetin has been found to have cardiovascular benefits. It can help improve blood vessel function, reduce blood pressure, inhibit the oxidation of low-density lipoprotein (LDL) cholesterol, and reduce the formation of blood clots. 
• Neuroprotective effects: quercetin has shown neuroprotective properties in preclinical studies. It can exert antioxidant and anti-inflammatory effects in the brain, potentially protecting against neurodegenerative diseases and cognitive decline. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Orally 

Headache 

Paresthesia  

Intravenous 

Dyspnea 

N/V 

Nephrotoxicity (>945 mg/sq. meter) 

Black Box Warning

Contraindication / Caution

Contraindications/caution: 

• Allergies: Some individuals may be allergic to quercetin or other flavonoids. If you have known allergies to foods or substances containing quercetin, it’s advisable to avoid its consumption or use with caution. 
• Pregnancy and breastfeeding: Limited information is available regarding the safety of quercetin supplementation during pregnancy and breastfeeding. Therefore, it’s recommended to exercise caution and consult with a healthcare professional before using quercetin supplements during these periods. 
• Drug interactions: quercetin may interact with certain medications. It can inhibit the activity of cytochrome P450 enzymes, which metabolize various drugs. This interference could affect the efficacy or safety of certain medications. If you are taking prescription medications, you must consult a healthcare professional before using quercetin to determine if any potential interactions or adjustments in medication doses are necessary. 
• Blood thinners and anticoagulants: quercetin may have mild anticoagulant properties. Therefore, individuals taking blood thinners or anticoagulant medications, such as warfarin, heparin, or aspirin, should use quercetin cautiously, as it may increase the risk of bleeding. 
• Kidney disorders: quercetin is primarily metabolized and excreted by the kidneys. If you have severe kidney disease or impaired kidney function, it’s advisable to exercise caution and consult with a healthcare professional before using quercetin supplements. 
• Gastrointestinal issues: quercetin may cause gastrointestinal side effects, such as stomach upset, diarrhea, or nausea, particularly when taken in high doses. If you have a history of gastrointestinal issues, it’s recommended to start with a low dose and monitor your body’s response. 

Pregnancy / Lactation

Pregnancy consideration: N/A 

Lactation: N/A 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

<b>Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

• Antioxidant activity: quercetin is a potent antioxidant that can scavenge free radicals and protect cells from oxidative stress. It helps prevent the damage caused by reactive oxygen species (ROS) and protects against oxidative damage to cellular components such as lipids, proteins, and DNA. 
• Anti-inflammatory effects: quercetin exhibits anti-inflammatory properties by inhibiting the production and release of inflammatory mediators, including cytokines, chemokines, and prostaglandins. It can modulate inflammatory signaling pathways, such as nuclear factor-kappa B (NF-kB) and mitogen-activated protein kinase (MAPK) pathways. 
• Immunomodulatory effects: quercetin can modulate the immune system by influencing immune cell function and cytokine production. It has been shown to enhance the activity of specific immune cells, such as natural killer (NK) cells and T lymphocytes. quercetin can also exert a regulatory effect on the immune response, helping to maintain immune balance. 
• Antiviral activity: quercetin has demonstrated antiviral properties against various viruses, including influenza, herpes simplex virus, respiratory syncytial virus, and coronaviruses. It can inhibit viral replication by various mechanisms, such as interfering with viral attachment and entry into host cells, blocking viral RNA synthesis, and inhibiting viral proteases. 
• Anticancer effects: quercetin has been studied for its potential anticancer properties. It can inhibit the growth and proliferation of cancer cells, induce apoptosis (programmed cell death), and inhibit angiogenesis (formation of new blood vessels to tumors). quercetin may also exhibit chemopreventive effects by preventing DNA damage and modulating key signaling pathways in cancer development and progression. 
• Cardiovascular effects: quercetin has shown cardiovascular benefits by improving endothelial function, reducing oxidative stress, and inhibiting low-density lipoprotein (LDL) cholesterol oxidation. It can help promote healthy blood vessel function, regulate blood pressure, and reduce the risk of cardiovascular diseases. 

Pharmacodynamics: 

• Enzyme inhibition: quercetin can inhibit the activity of several enzymes involved in various cellular processes. For example, it can inhibit enzymes such as xanthine oxidase, which is involved in the production of uric acid, and aldose reductase, which is associated with diabetic complications. By modulating enzyme activity, quercetin can impact physiological processes and contribute to its therapeutic effects. 
• Ion channel modulation: quercetin can interact with ion channels, such as calcium and potassium channels, thereby modulating their activity. This modulation can affect cellular excitability and neurotransmitter release, contributing to its potential neuroprotective effects and influencing cardiovascular function. 

Pharmacokinetics: 

Absorption 

quercetin is generally well-absorbed in the gastrointestinal tract, but various factors influence its absorption. Its bioavailability could be higher due to poor water solubility, limited stability, and extensive metabolism. The absorption of quercetin can be enhanced by co-administration with certain compounds, such as piperine, which inhibits metabolism and improves its bioavailability. 

Distribution 

quercetin is distributed throughout the body after absorption. It can cross cell membranes and distribute into various tissues, including the liver, kidney, heart, and brain. However, its distribution may be limited by its high binding affinity to plasma proteins 

Metabolism 

quercetin undergoes extensive metabolism in the body, primarily in the liver. It is metabolized through phase II conjugation reactions, including glucuronidation, sulfation, and methylation. These metabolic pathways help to increase its water solubility and facilitate its excretion. quercetin can also undergo phase I metabolism, including oxidation and hydroxylation reactions, mediated by enzymes such as cytochrome P450 (CYP) enzymes. 

Elimination and Excretion 

quercetin and its metabolites are excreted primarily via the feces and urine. The glucuronide and sulfate conjugates of quercetin are eliminated in the urine, while the parent compound and other metabolites can be excreted in the feces. The elimination half-life of quercetin is relatively short, ranging from a few hours to about 24 hours. 

Adminstartion

Administration: 

quercetin can be administered through various routes, depending on the desired therapeutic effect and available formulations.  

• Oral administration: The most common and convenient way to take quercetin is orally, usually through dietary supplements or natural food sources. quercetin supplements are available in capsule, tablet, or powder form. It is recommended to follow the instructions provided by the manufacturer or healthcare professional regarding the dosage and timing of oral quercetin supplementation. 
• Food sources: quercetin is naturally present in many fruits, vegetables, and herbs. Consuming a diet rich in these food sources can provide a natural intake of quercetin. Some foods high in quercetin include apples, berries (such as blueberries and cranberries), citrus fruits, onions, kale, broccoli, and green tea. 
• Intravenous administration: In specific clinical settings, quercetin may be administered intravenously (IV) for specific purposes. This route allows for direct delivery of quercetin into the bloodstream, bypassing the gastrointestinal absorption process. However, intravenous administration of quercetin is less common and typically used in research or clinical settings. 
• Topical application: quercetin can be applied topically to the skin through creams, ointments, or lotions. This method is commonly used in skincare products, as quercetin’s antioxidant and anti-inflammatory properties may benefit the skin. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: quercetin 

Why do we use quercetin? 

quercetin has been studied for its potential health benefits and therapeutic uses. 

• Antioxidant support: quercetin acts as a potent antioxidant, helping to neutralize free radicals and reduce oxidative stress. It may contribute to overall cellular health and support the body’s natural defence against oxidative damage. 
• Anti-inflammatory properties: quercetin has shown anti-inflammatory effects by inhibiting the production and release of inflammatory mediators. It may help reduce inflammation associated with chronic conditions such as arthritis, allergies, and inflammatory bowel disease. 
• Allergy relief: quercetin has been investigated for its potential to alleviate allergy symptoms. It may help stabilize mast cells and reduce the release of histamine, which can contribute to allergic reactions. 
• Cardiovascular health: quercetin has been studied for its cardiovascular benefits. It promotes healthy blood vessel function, reduces blood pressure, improves endothelial function, and reduces the oxidation of LDL cholesterol. These effects may contribute to a reduced risk of cardiovascular diseases. 
• Immune support: quercetin has been shown to modulate the immune system by influencing immune cell function and cytokine production. It may help support a balanced immune response and improve overall immune health. 
• Exercise performance and recovery: Some studies suggest that quercetin may improve exercise performance and aid in post-exercise recovery. It may help reduce exercise-induced oxidative stress and inflammation, improving endurance and reducing muscle damage. 
• Potential anticancer effects: quercetin has been studied for its potential anticancer properties. It has shown inhibitory effects on cancer cell growth, induction of apoptosis (programmed cell death), and modulation of signalling pathways involved in cancer development and progression. However, more research is needed to understand its full potential in cancer prevention and treatment. 
• Skin health: quercetin’s antioxidant and anti-inflammatory properties may benefit skin health. It may help protect the skin against oxidative damage, reduce inflammation, and promote overall health and appearance.