Interactions on record — worth a quick check against your medications. Based on 2 of 4 ingredients. Check your meds →
Dietary supplement

Energy Enhancer N.O. Ingredients & Drug Interactions

by GNC Pro Performance AMP

Energy Enhancer N.O. label
See full label image
Tablet Or Pill Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Energy Enhancer N.O. against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Energy Enhancer N.O. is a dietary supplement by GNC Pro Performance AMP with 4 active ingredients. Its ingredients are commonly taken for high cholesterol, vitamin b3 deficiency (pellagra), heart health support.Based on those ingredients, 1,256 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are MegaNatural(R)-BP(TM) Grape Seed Extract, Niacin. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Energy Enhancer N.O. by GNC Pro Performance AMP

Ask about any prescription or over-the-counter medication and we check it for interactions with Energy Enhancer N.O. by GNC Pro Performance AMP — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Energy Enhancer N.O. by GNC Pro Performance AMP

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 23, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 4 of its 4 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Energy Enhancer N.O. contains four ingredients: niacin (a B vitamin), L-Arginine (an amino acid), MegaNatural-BP grape seed extract, and PEG. The product also includes inactive ingredients—calcium carbonate, enteric coating, titanium dioxide, vegetable acetoglycerides, and sodium copper chlorophyllins—that serve as fillers and binders.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: enhance blood flow and power output during exercise.
  • We looked for evidence on: Athletic performance, Erectile Dysfunction (ED), Exercise performance, Nitric oxide production.
  • The closest evidence on file: Grape is rated "Insufficient Reliable Evidence To Rate" for Athletic performance (Natural Medicines).
  • Also on file: Grape is rated "Insufficient Reliable Evidence To Rate" for Erectile Dysfunction (ED).
  • Also on file: Niacin is rated "Insufficient Reliable Evidence To Rate" for Athletic performance, Erectile dysfunction (ED).

Niacin is likely effective for pellagra (a B vitamin deficiency disease) and possibly effective for certain types of abnormal blood fat levels tied to HIV/AIDS and metabolic syndrome. Grape seed extract is possibly effective for chronic venous insufficiency (poor circulation in the legs) but was found possibly ineffective for chemotherapy-induced nausea, hay fever, and weight loss in studies we hold.

We have no effectiveness data on file for L-Arginine or PEG in this product.

The evidence, ingredient by ingredient Niacin Grape

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Niacin from food is safe, but high supplemental doses can cause flushing (a common side effect affecting up to 70% of people), stomach upset, and liver problems. Serious side effects are rare but include liver damage, muscle damage, low platelet counts, and vision changes.

High-dose niacin should be avoided in pregnancy unless prescribed by your doctor; amounts from food and standard prenatal vitamins are fine. During breastfeeding, normal dietary intake is safe, but avoid high-dose supplements without medical guidance.

Grape seed extract is generally well tolerated; the most common side effects are abdominal pain, diarrhea, dry mouth, heartburn, headache, joint pain, and nausea. Grape seed is likely safe in pregnancy and breastfeeding, though concentrated supplements during pregnancy have limited safety data and should be discussed with your doctor.

Side effects, ingredient by ingredient Niacin Grape

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 2 of the 2 matched ingredients can interact with medications — Grape, Niacin.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; diabetes medications.
  • For scale: 1,257 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, check with your doctor or pharmacist if you take any blood thinners or antiplatelet drugs (like warfarin or aspirin)—both niacin and grape seed extract may increase bleeding risk. Blood pressure medicines, diabetes medications, statins, gout drugs, and any drug metabolized by liver enzymes CYP1A2, CYP2D6, CYP2E1, or CYP3A4 all need review.

If you take cyclosporine, bile acid sequestrants, or phenacetin, separate timing or alternative approaches may be needed.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

If you're on blood pressure medications, diabetes drugs, blood thinners, cholesterol-lowering statins, or gout medications, talk with your doctor or pharmacist before taking this product—niacin's effects on these drugs need checking. The same applies if you take any medication processed by your liver.

The grape seed extract adds further enzyme interactions worth reviewing. If you're pregnant or breastfeeding, discuss high-dose niacin with your healthcare provider before starting.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 2 of 4 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Feb 23, 2012.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Energy Enhancer N.O., straight from the product label.

Brand GNC Pro Performance AMP
Market status On market
Date entered into DSLD Feb 23, 2012
DSLD ID 5819
Product type Other Combinations
Supplement form Tablet Or Pill
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult Male (18-50 Years), Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Energy Enhancer N.O. by GNC Pro Performance AMP, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
3 Tablet(s)
Maximum serving Sizes:
3 Tablet(s)
IngredientAmount% DV
Niacin10 mg50%
L-Arginine, Micronized1500 mg--
MegaNatural(R)-BP(TM) Grape Seed Extract300 mg--
PEG150 mg--

Other ingredients: Calcium Carbonate, Enteric Coating, Titanium Dioxide, Vegetable Acetoglycerides, Sodium Copper Chlorophyllins, Sodium Copper Chlorophyllin

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
FDA Disclaimer Statement

* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

General Statements

In a randomized, double blind, placebo controlled study, 50 healthy untrained male volunteers were given Energy Enhancer N.O. or a placebo. Each subject exercised on a cycle ergometer prior to receiving the supplement or placebo and again after the treatment period was finished. Those subjects supplemented with Energy Enhancer N.O. had a 20% increase in PWCFT (physical working capacity at the fatigue threshold) after four weeks of supplementation relative to the placebo group.

ACTUAL SIZE

Energy Enhancer N.O.

Energy Enhancer N.O. – This advanced nitric oxide product provides 1.5g of micronized arginine and is included to help increase your power output at the onset of fatigue 20%.† It’s clinically studied and designed to enhance blood flow and amplify your intense workouts.* Technologically enhanced for better absorption to maximize muscle performance capacity and give your body the push it needs to go above and beyond your regular workouts.

GNC QUALITY COMMITMENT GNC, the leader in the development and manufacture of dietary supplements, is committed to producing the highest quality products available. This commitment begins with quality designed supplement formulations. Every raw material that goes into a GNC supplement is guaranteed as to quality and potency. Each product is dated and then shipped immediately to our stores, so you can be sure you are purchasing the freshest supplements available. At GNC, we extend our quality commitment to you by offering our money-back guarantee.

To maximize total endurance and energy support, use with: • Amplified Endurance Booster – loaded with electrolytes, carbohydrates and BCAA to replenish glycogen stores fast* • Amplified 100% Whey Protein – with fast-absorbing protein to fuel your training*

Clinically Researched^

ADVANCED MUSCLE PERFORMANCE

ADVANCED SPORTS VITAMIN SYSTEM TO AMPLIFY ENDURANCE WITH OVER 50 POWERFUL INGREDIENTS*

Daily Endurance Energy Stamina

Each pak contains:

GNC GUARANTEE Use any GNC supplement for as little as 10 days. If you are not 100% completely satisfied, return the unused portion of the product with proof of purchase to your GNC store for a complete refund of your purchase price. No questions asked!

Brand IP Statement(s)

MegaNatural(R)-BP(TM) and its logo are trademarks of Constellation Wines U.S., Inc.

The Pro Performance(R) AMP Endurance Vitapak(R) Program Evolution Driving this elite performance breakthrough is a mechanism that supports enhanced blood flow and oxygen uptake at the most critical time during training – at the onset of fatigue. Using an unmatched clinically proven module, it unleashes a 20% boost in workout intensity.† Most athletes today are not combining the proper combinations and ratios of critical sports nutrition. This system, used by elite runners, cyclists and other hardcore athletes, delivers precisely what muscles need to fuel difficult training, help your body recover and prepare to do it again. This exclusive nutrient system amplifies total muscle performance, increases intensity at the onset of fatigue, fuels cardio training, improves performance and ramps up energy production.* Mega Men(R) Sport – This high-potency clinically studied^ sports multivitamin formula includes critical components to fill important nutrient gaps in regular supplementation programs. Mega Men(R) Sport contains B-vitamins that are important for energy production and carbohydrate metabolism.* It provides amino acids, including BCAA, and a joint cushioning blend for healthy joint cartilage.* Also features a broad spectrum of cell-protecting antioxidants and nutrients that aid in boosting immunity.*

What is Pro Performance(R) AMP Endurance Vitapak(R) Program? The power to endure intense physical training and extreme cardiovascular sessions requires absolute fine-tuning of your sports nutrition regimen to enable the body to perform at peak levels. The most perfectly trained athletes know that you must have an effective, targeted and balanced nutrition regimen to achieve maximum training benefits. GNC Scientists have created the breakthrough Pro Performance(R) AMP Endurance Vitapak(R) Program. The unparalleled power of over 50 premium, athletic-boosting ingredients combine together to amplify physical and mental intensity, delivering a total performance boost of 20%. This powerful combination of a daily premium multivitamin, sports nutrients and clinically studied ingredients delivers the edge athletes want to perform.

Seals/Symbols

MegaNatural(R)-BP

Precautions

Consult your physician prior to using this product if you are pregnant, nursing, taking medication, allergic or contraindicated to aspirin, or have a medical condition. Discontinue use two weeks prior to surgery, or if upset stomach occurs.

Consult your physician prior to using this product if you are pregnant, nursing, taking medication, allergic or contraindicated to aspirin, or have a medical condition. Discontinue use two weeks prior to surgery, or if upset stomach occurs.

KEEP OUT OF REACH OF CHILDREN.

Formulation

No Wheat, No Gluten, No Dairy, Yeast Free.

FDA Statement of Identity

Dietary supplement

Suggested/Recommended/Usage/Directions

DIRECTIONS: As a dietary supplement, take the contents of one pak 30-60 minutes pre-workout. On non-training days, take the contents of one pak first thing in the morning with food. Do not exceed one pak daily.

Storage

Store in a cool, dry place.

General

CODE 331311 CMG

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Energy Enhancer N.O. by GNC Pro Performance AMP label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Energy Enhancer N.O. label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Energy Enhancer N.O. by GNC Pro Performance AMP

These are the 4 active ingredients this product is made of. Select any to open its full monograph.

Serving size3 Tablet(s) Dosage formTablet Or Pill Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Niacin

Interacts with
727 drugs
10 mg per serving

Niacin (vitamin B3) is an essential nutrient your body needs for energy and metabolism, and deficiency is uncommon in most developed countries. Prescr...

Niacin monograph & interactions

L-Arginine, Micronized

1500 mg per serving

MegaNatural(R)-BP(TM) Grape Seed Extract

Interacts with
910 drugs
300 mg per serving

Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and b...

MegaNatural(R)-BP(TM) Grape Seed Extract monograph & interactions

PEG

150 mg per serving

Other (inactive) ingredients: Calcium Carbonate, Enteric Coating, Titanium Dioxide, Vegetable Acetoglycerides, Sodium Copper Chlorophyllins, Sodium Copper Chlorophyllin. These complete the product’s ingredient list but are not active constituents.

Interaction report

Energy Enhancer N.O. by GNC Pro Performance AMP Drug Interactions

Want to check YOUR meds against Energy Enhancer N.O.?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,256Drugs
1,245 Moderate 11 Minor

Ingredients driving the most interactions

MegaNatural(R)-BP(TM) Grape Seed Extract 910
Niacin 727

Individual Drug Interactions

The ingredients in Energy Enhancer N.O. interact with 1,256 drugs. Click any drug to see the details.

2 of the 4 ingredients in Energy Enhancer N.O. interact with drugs. Each result below shows which ingredient is responsible. MegaNatural(R)-BP(TM) Grape Seed Extract Niacin

Each ingredient & the kinds of drugs it affects

For each ingredient in Energy Enhancer N.O. with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

MegaNatural(R)-BP(TM) Grape Seed Extract9 drug types · 910 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, grape extracts may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
In vitro evidence suggests that grape extracts might decrease platelet aggregation.

Likelihood Possible Evidence D
Cyclosporine (Neoral, Sandimmune)

Ingesting grape juice with cyclosporine can reduce cyclosporine absorption.
A small pharmacokinetic study in healthy young adults shows that intake of purple grape juice 200 mL along with cyclosporine can decrease the absorption of cyclosporine by up to 30% when compared with water. Separate doses of grape juice and cyclosporine by at least 2 hours to avoid this interaction.

Likelihood Possible Evidence B
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of CYP1A2.

Likelihood Possible Evidence B
Cytochrome P450 2D6 (Cyp2D6) Substrates

Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
In vitro evidence suggests that grape seed extract might inhibit CYP2D6 enzymes. However, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, grape seed extract might increase the levels of CYP2E1 substrates.
In vitro and animal research suggests that grape seed proanthocyanidin extract inhibits CYP2E1 enzymes. However, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
In vitro evidence suggests that grape seed extract might inhibit CYP3A4 enzymes. However, evidence from animal research shows that grape seed extract may induce CYP3A4 in the liver. So far, these interactions have not been reported in humans.

Likelihood Possible Evidence D
Midazolam (Versed)

Theoretically, long-term intake of grape seed extract might decrease the effects of midazolam.
Animal research shows that subchronic ingestions of grape seed extract can increase the elimination of intravenous midazolam by increasing hepatic CYP3A4 activity. Single doses of grape seed extract do not appear to affect midazolam elimination.

Likelihood Possible Evidence D
Phenacetin

Grape juice might decrease phenacetin absorption.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of cytochrome P450 1A2 (CYP1A2).

Likelihood Possible Evidence B
Cytochrome P450 2C9 (Cyp2C9) Substrates

It is unclear if grape juice or grape seed extract inhibits CYP2C9; research is conflicting.
In vitro evidence shows that grape seed extract or grape juice might inhibit CYP2C9 enzymes. However, a small pharmacokinetic study in healthy adults shows that drinking 8 ounces of grape juice once does not affect the clearance of flurbiprofen, a probe-drug for CYP2C9 metabolism. The effects of continued grape juice consumption are unclear.

Likelihood Unlikely Evidence D
MegaNatural(R)-BP(TM) Grape Seed Extract full monograph & interactions

Niacin15 drug types · 727 drugs

Alcohol (Ethanol)

Concomitant use of alcohol and niacin might increase the risk of flushing and hepatotoxicity.
Alcohol can exacerbate the flushing and pruritus associated with niacin. Large doses of niacin might also exacerbate liver dysfunction associated with chronic alcohol use. A case report describes delirium and lactic acidosis in a patient taking niacin 3 grams daily who ingested 1 liter of wine. Advise patients to avoid large amounts of alcohol while taking niacin.

Likelihood Probable Evidence D
Allopurinol (Zyloprim)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as allopurinol.
Large doses of niacin can reduce urinary excretion of uric acid, potentially resulting in hyperuricemia. Doses of uricosurics such as allopurinol might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C
Anticoagulant/Antiplatelet Drugs

Theoretically, niacin may have additive effects when used with anticoagulant or antiplatelet drugs.
Several cases of clotting factor synthesis deficiency and coagulopathy have been reported in patients taking sustained-release niacin. Also, thrombocytopenia has been reported in patients treated with niacin or niacin plus lovastatin.

Likelihood Possible Evidence D
Antidiabetes Drugs

Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.
Niacin impairs glucose tolerance in a dose-dependent manner, probably by causing or aggravating insulin resistance and increasing hepatic production of glucose. In diabetes patients, niacin 4.5 grams daily for 5 weeks can increase plasma glucose by an average of 16% and glycated hemoglobin (HbA1c) by 21%. However, lower doses of 1.5 grams daily or less appear to have minimal effects on blood glucose. In some patients, glucose levels increase when niacin is started, but then return to baseline when a stable dose is reached. Up to 35% of patients with diabetes may need adjustments in hypoglycemic therapy when niacin is added.

Likelihood Probable Evidence B
Antihypertensive Drugs

Theoretically, niacin may increase the risk of hypotension when used with antihypertensive drugs.
The vasodilating effects of niacin can cause hypotension. Furthermore, some clinical evidence suggests that a one-hour infusion of niacin can reduce systolic, diastolic, and mean blood pressure in hypertensive patients. This effect is not observed in normotensive patients.

Likelihood Possible Evidence B
Bile Acid Sequestrants

Bile acid sequestrants can bind niacin and decrease absorption. Separate administration by 4-6 hours to avoid an interaction.
In vitro studies show that colestipol (Colestid) binds about 98% of available niacin and cholestyramine (Questran) binds 10% to 30%.

Likelihood Possible Evidence D
Gemfibrozil (Lopid)

Theoretically, concomitant use of niacin and gemfibrozil might increase the risk of myopathy in some patients.
A case of myopathy from concomitant use of niacin and gemfibrozil has been reported. Niacin alone has also been associated with cases of myopathy. Using gemfibrozil with niacin might further increase the risk of developing myopathy.

Likelihood Possible Evidence D
Hepatotoxic Drugs

Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.
Niacin has been associated with cases of liver toxicity, especially when used in pharmacologic doses. Sustained-release niacin preparations appear to be associated with a higher risk of hepatotoxicity than immediate-release niacin.

Likelihood Possible Evidence D
Hmg-Coa Reductase Inhibitors ("Statins")

Theoretically, concomitant use of niacin and statins might increase the risk of myopathy and rhabdomyolysis in some patients.
Some case reports have raised concerns that niacin might increase the risk of myopathy and rhabdomyolysis when combined with statins. However, a significantly increased risk of myopathy has not been demonstrated in clinical trials, including those using an FDA-approved combination of lovastatin and niacin (Advicor).

Likelihood Possible Evidence D
Probenecid (Benemid)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as probenecid.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as probenecid might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C
Sulfinpyrazone (Anturane)

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as sulfinpyrazone.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as sulfinpyrazone might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Likelihood Probable Evidence C
Thyroid Hormone

Theoretically, niacin might antagonize the therapeutic effects of thyroid hormones.
Clinical research and case reports suggests that taking niacin can reduce serum levels of thyroxine-binding globulin by up to 25% and moderately reduce levels of thyroxine (T4). Patients taking thyroid hormone for hypothyroidism might need dose adjustments when using niacin.

Likelihood Probable Evidence D
Transdermal Nicotine (Nicoderm)

Theoretically, concomitant use of niacin and transdermal nicotine might increase the risk of flushing and dizziness.
Niacin and nicotine can both cause flushing and dizziness.

Likelihood Possible Evidence D
Warfarin (Coumadin)

There is limited evidence that niacin may increase the anticoagulant effects of warfarin.
In a case report, a patient on warfarin developed an elevated international normalized ratio (INR) of 3.9 after taking niacin for two weeks. The patient's INR was previously stable, ranging between 2 and 3 in recent months, and no other medication changes were identified. The elevated INR returned to therapeutic range within 4 days following the discontinuation of niacin.

Likelihood Possible Evidence D
Aspirin

Large doses of aspirin might alter the clearance of niacin.
Aspirin is often used with niacin to reduce niacin-induced flushing. Doses of 80-975 mg aspirin have been used, but 325 mg appears to be optimal. Aspirin also seems to reduce the clearance of niacin by competing for glycine conjugation. Taking aspirin 1 gram seems to reduce niacin clearance by 45%. This is probably a dose-related effect and not clinically significant with the more common aspirin dose of 325 mg.

Likelihood Likely Evidence B
Niacin full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Energy Enhancer N.O., from the product label.

GNC Pro Performance AMP

See all GNC Pro Performance AMP products
Phone Number
1-888-462-2548
Pharmacist Counseling Corner

Energy Enhancer N.O. by GNC Pro Performance AMP: Common Questions

Does Energy Enhancer N.O. by GNC Pro Performance AMP interact with any medications?
Yes. Based on its ingredients, Energy Enhancer N.O. has a known interaction with 1,256 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Energy Enhancer N.O. contains 4 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
What does niacin do in this product?
Niacin is a B vitamin that supports energy and blood fat metabolism. In supplement form, it's used to help raise 'good' cholesterol and lower triglycerides, and it's proven effective for pellagra, a B vitamin deficiency.
What's the grape seed extract for?
Grape seed extract is a concentrated plant compound that may help with chronic venous insufficiency—poor circulation in the legs that causes swelling and heaviness—though it was ineffective in studies for hay fever, nausea, and weight loss.
Will I get flushing from niacin in this product?
Flushing—redness, warmth, tingling, and itching of the face and neck—is common with niacin supplements. Up to 70% of people experience it, especially at higher doses. It typically eases after a few weeks or if you take the supplement with food or an antacid.
Is this product safe if I'm pregnant?
Food amounts of niacin and standard prenatal vitamin doses are safe in pregnancy. High-dose niacin supplements should only be used if your doctor prescribes them. Grapes and grape seed extract have limited safety data in pregnancy, so talk with your doctor before starting.
Can I take this if I'm breastfeeding?
Normal dietary niacin and niacin from food sources are safe. High-dose niacin supplements aren't well studied during breastfeeding—check with your doctor. We don't have enough information on concentrated grape seed supplements while breastfeeding, so discuss it with your healthcare provider.
What are the most common side effects?
From niacin: flushing, stomach upset (nausea, heartburn, diarrhea, constipation, abdominal pain), and elevated liver enzymes. From grape seed extract: abdominal pain, diarrhea, dry mouth, heartburn, headache, joint pain, and nausea. Niacin side effects often improve within two weeks or with food.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Energy Enhancer N.O. label
Go deeper

The Full Monographs Behind Energy Enhancer N.O.’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Niacin

Interacts with 727 drugs

Niacin (vitamin B3) is an essential nutrient your body needs for energy and metabolism, and deficiency is uncommon in most developed countries. Prescription-strength niacin has been used to...

Read the full Niacin monograph → Herb & supplement monograph

Grape

Interacts with 910 drugs

Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and blood vessel health. While the food is he...

Read the full Grape monograph →
Sources

Sources & How We Checked

Energy Enhancer N.O.'s label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 100 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Niacin 66 references
  1. Garg R, Malinow MR, Pettinger M, et al. Niacin treatment increases plasma homocysteine levels. Am Heart J 1999;138:1082-7.
  2. Anon. Inositol hexaniacinate. Altern Med Rev 1998;3:222-3.
  3. Knodel LC, Talbert RL. Adverse effects of hypolipidaemic drugs. Med Toxicol 1987;2:10-32. PubMed
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Grape 34 references
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See these in context on the Grape monograph →

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