21st Century L-Arginine 500mg Plus Capsule

21st Century L-Arginine 500mg Plus Capsule is an amino acid dietary supplement from 21st Century, a US supplement brand. Each capsule provides 500mg of L-arginine, and the “Plus” in the name refers to added nutrients: the product information lists vitamin B6, magnesium and zinc alongside the L-arginine. The amounts of these added nutrients, and any other ingredients, should be confirmed on the product label. It is supplied as oral capsules in a pack of 30.

L-arginine is a conditionally essential amino acid that the body both produces and obtains from protein foods such as meat, fish, dairy, nuts and legumes. It is used to build proteins, takes part in the urea cycle, and is a starting material for creatine and several signalling molecules. Vitamin B6 contributes to normal protein and amino acid metabolism, magnesium is involved in normal muscle function and energy-yielding metabolism, and zinc contributes to normal protein synthesis and immune function.

This capsule may be used as a dietary supplement by adults who want a moderate amount of L-arginine together with these supporting micronutrients. Because it contains vitamins and minerals as well as L-arginine, check whether you already take a multivitamin or a zinc or magnesium supplement to avoid unnecessary duplication. Adults taking nitrates, PDE5 inhibitors such as sildenafil or tadalafil, blood pressure medicines or certain antibiotics, and anyone with a history of heart attack, should speak to a doctor or pharmacist before use.

Swallow the capsule whole with a glass of water, ideally with a meal to reduce the chance of stomach discomfort. Try to take it at around the same time each day. If you take antibiotics or other medicines affected by minerals, space them apart as advised by your pharmacist. Always follow the directions printed on the product label or the advice of your healthcare professional.

Adults: the product information indicates 1 to 2 capsules daily, preferably with meals, or as directed by a healthcare professional. Please confirm the recommended dose on the product label, as label directions take priority.

Do not exceed the recommended daily intake, and take into account any vitamin B6, magnesium or zinc you already get from other supplements. This product is not intended for children or adolescents.

Store in a cool, dry place, away from direct sunlight, heat and moisture. Keep the container tightly closed after each use and keep it out of reach of children. Follow any additional storage instructions printed on the product label.

• Common: stomach discomfort, bloating, nausea or abdominal cramps, which are more likely at higher intakes.
• Common: diarrhoea or loose stools, especially when the product is taken in larger amounts.
• Common: headache or mild flushing in some people.
• Less common: dizziness or light-headedness related to a drop in blood pressure, particularly when combined with blood pressure medicines.
• Less common: zinc can cause nausea or a metallic taste, and magnesium can loosen stools, particularly when combined with other supplements containing these minerals.
• Serious: allergic reactions such as rash, itching, swelling of the face, lips or throat, or difficulty breathing; worsening of asthma symptoms has also been reported with L-arginine. Stop use and seek urgent medical attention.

• People who have had a recent heart attack: L-arginine is not recommended after a heart attack, as a clinical study in this group raised safety concerns.
• People taking nitrates for angina or chest pain, unless specifically approved by their doctor.
• People with low blood pressure, or those prone to dizziness or fainting.
• People with a history of herpes infections (including cold sores), as L-arginine may support herpes virus activity in laboratory studies.
• People with known allergy or hypersensitivity to L-arginine, vitamin B6, magnesium, zinc or any other ingredient in the product.
• People with guanidinoacetate methyltransferase (GAMT) deficiency, an inherited disorder of creatine metabolism.

• Nitrates (e.g. glyceryl trinitrate, isosorbide mononitrate or dinitrate, used for angina): L-arginine may add to the blood-pressure-lowering effect of nitrates and increase the risk of dizziness or fainting. Do not combine without your doctor’s advice.
• PDE5 inhibitors (e.g. sildenafil, tadalafil): taking L-arginine together with a PDE5 inhibitor may cause an additive drop in blood pressure. Speak to your doctor or pharmacist before combining them.
• Blood pressure medicines (e.g. ACE inhibitors, angiotensin receptor blockers, calcium channel blockers, beta blockers, diuretics): there may be an additive blood-pressure-lowering effect, so your blood pressure may need closer monitoring.
• ACE inhibitors, angiotensin receptor blockers and potassium-sparing diuretics (e.g. spironolactone): L-arginine may raise blood potassium levels, particularly in people with reduced kidney function.
• Diabetes medicines: L-arginine may influence blood sugar levels, so people taking glucose-lowering medicines should monitor their readings and speak to their doctor.
• Tetracycline and quinolone antibiotics (e.g. doxycycline, ciprofloxacin) and some osteoporosis medicines (bisphosphonates): magnesium and zinc can reduce their absorption. Take these medicines at least 2 hours before or 4 to 6 hours after this supplement, or as your pharmacist advises.
• Multivitamins and mineral supplements: taking them together may add up your intake of vitamin B6, zinc and magnesium; long-term high intakes of vitamin B6 have been linked to nerve problems such as numbness or tingling.

• Take the capsule with breakfast or another main meal to keep it gentle on the stomach.
• Add up the vitamin B6, zinc and magnesium in all your supplements so you do not take more than you need.
• Leave a gap between this supplement and antibiotics such as doxycycline or ciprofloxacin.
• Tell your doctor you take L-arginine before starting heart, blood pressure or PDE5 inhibitor medicines.
• Stop taking it at least two weeks before planned surgery.
• Report any numbness or tingling in your hands or feet to your doctor or pharmacist.

Precautions: This product is intended for adults. There is not enough reliable information on the safety of supplemental L-arginine during pregnancy or breastfeeding, so do not use it during these times unless your doctor advises it. Use with caution if you have kidney disease, liver disease, diabetes, asthma or allergies, or if you are taking any blood pressure, heart or diabetes medicines. Stop taking the product at least two weeks before planned surgery, as it may affect blood pressure. Avoid taking several products containing L-arginine, vitamin B6, zinc or magnesium at the same time without checking the total amounts.

When to See a Doctor or Pharmacist: Speak to a doctor or pharmacist before use if you have heart disease, a history of heart attack, low or high blood pressure, kidney problems or recurrent herpes infections, or if you take nitrates, PDE5 inhibitors such as sildenafil or tadalafil, or blood pressure medicines. Stop using the product and seek medical attention promptly if you develop chest pain, fainting, severe dizziness, a rash, swelling of the face or lips, or difficulty breathing.