Herb & supplement monograph

Ilex Guayusa Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Ilex Guayusa interacts with medications. The heart of this page is the interaction list — every drug Ilex Guayusa is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Ilex Guayusa is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Ilex Guayusa Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Ilex Guayusa drug interactions come almost entirely from its caffeine content, and for most people the overall risk of a clinically significant interaction is moderate rather than severe. Only a small handful of the listed interactions are rated major, and most of the rest are moderate, caffeine-related effects with varying levels of evidence.

Interactions deserving the most attention

The clearest concern is combining Ilex Guayusa with ephedrine or other stimulant medications, since adding caffeine can raise the risk of serious effects on blood pressure and the heart. Human studies also show that cimetidine, fluvoxamine, disulfiram, and birth control pills slow the body's clearance of caffeine, which can amplify jitteriness, fast heartbeat, and trouble sleeping. Animal research suggests caffeine might weaken some seizure medicines, such as phenytoin and valproate, so extra care makes sense where seizure control matters.

What the rest of the list means

A long interaction list does not mean every combination is harmful. Most entries here are theoretical, based on how caffeine might affect enzymes the body uses to clear certain medications. Some predicted problems, such as added bleeding risk with blood thinners, have not actually been shown to occur in people.

Check your medications against Ilex Guayusa

Based on HelloPharmacist’s Ilex Guayusa interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Ilex Guayusa

605 medications have a known interaction with Ilex Guayusa, graded by severity. Select any drug for the full evidence-based detail.

8 major interactions. These combinations can be clinically significant — best avoided, or used only with close professional supervision. Always check with your pharmacist before combining them with Ilex Guayusa.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Ilex Guayusa using our pharmacist-reviewed interaction data.

AI summaries are generated from our Ilex Guayusa interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Ilex Guayusa combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Ilex Guayusa affects

Every type of medication (drug category) Ilex Guayusa is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 37 drug categories Ilex Guayusa interacts with

EphedrineAdenosine (adenocard)Anticoagulant/antiplatelet DrugsBeta-adrenergic AgonistsCimetidine (tagamet)Clozapine (clozaril)Contraceptive DrugsDipyridamole (persantine)Disulfiram (antabuse)Diuretic DrugsEstrogensFlutamide (eulexin)Fluvoxamine (luvox)LithiumMonoamine Oxidase Inhibitors (maois)NicotinePentobarbital (nembutal)Phenobarbital (luminal)PhenylpropanolaminePhenytoin (dilantin)Pioglitazone (actos)Riluzole (rilutek)Stimulant DrugsTheophyllineValproateVerapamil (calan, Others)Alcohol (ethanol)Antidiabetes DrugsFluconazole (diflucan)Metformin (glucophage)Methoxsalen (oxsoralen)Mexiletine (mexitil)PhenothiazinesQuinolone AntibioticsTerbinafine (lamisil)Tiagabine (gabitril)Ticlopidine (ticlid)

Ephedrine

Theoretically, concomitant use might increase the risk of stimulant adverse effects.
Ilex guayusa contains caffeine. There is evidence that using ephedrine with caffeine might increase the risk of serious life-threatening or debilitating adverse effects such as hypertension, myocardial infarction, stroke, seizures, and death. Tell patients to avoid taking caffeine with ephedrine and other stimulants.

Likelihood Probable Evidence D

Adenosine (Adenocard)

Theoretically, Ilex guayusa might decrease the vasodilatory effects of adenosine and interfere with its use prior to stress testing.
Ilex guayusa contains caffeine. Caffeine is a competitive inhibitor of adenosine at the cellular level. However, caffeine does not seem to affect supplemental adenosine because high interstitial levels of adenosine overcome the antagonistic effects of caffeine. It is recommended that methylxanthines such as caffeine, as well as methylxanthine-containing products, be stopped 24 hours prior to pharmacological stress tests. However, methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing.

Likelihood Possible Evidence D

Anticoagulant/Antiplatelet Drugs

Theoretically, Ilex guayusa may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Ilex guayusa contains caffeine. Caffeine is reported to have antiplatelet activity. Theoretically, caffeine in Ilex guayusa might increase the risk of bleeding when used concomitantly with these agents. However, this interaction has not been reported in humans. There is some evidence that caffeinated coffee might increase the fibrinolytic activity in blood.

Likelihood Unlikely Evidence D

Beta-Adrenergic Agonists

Theoretically, concomitant use of large amounts of Ilex guayusa might increase cardiac inotropic effects of beta-agonists.
Ilex guayusa contains caffeine. Caffeine can increase cardiac inotropic effects of beta-agonists.

Likelihood Probable Evidence D

Cimetidine (Tagamet)

Theoretically, cimetidine might increase the effects and adverse effects of caffeine in Ilex guayusa.
Ilex guayusa contains caffeine. Cimetidine can reduce caffeine clearance by 31% to 42%.

Likelihood Likely Evidence B

Clozapine (Clozaril)

Theoretically, Ilex guayusa might increase the levels and adverse effects of clozapine and acutely exacerbate psychotic symptoms.
Ilex guayusa contains caffeine. Caffeine can increase the effects and toxicity of clozapine. Caffeine doses of 400-1000 mg daily inhibit clozapine metabolism. Clozapine is metabolized by cytochrome P450 1A2 (CYP1A2). Researchers speculate that caffeine might inhibit CYP1A2. However, there is no reliable evidence that caffeine affects CYP1A2. There is also speculation that genetic factors might make some patients more sensitive to an interaction between clozapine and caffeine.

Likelihood Possible Evidence B

Contraceptive Drugs

Theoretically, concomitant use might increase the effects and adverse effects of caffeine found in Ilex guayusa.
Ilex guayusa contains caffeine. Oral contraceptives decrease the rate of caffeine clearance by 40% to 65%.

Likelihood Probable Evidence B

Dipyridamole (Persantine)

Theoretically, Ilex guayusa might decrease the vasodilatory effects of dipyridamole and interfere with its use prior to stress testing.
Ilex guayusa contains caffeine. Caffeine is a methylxanthine that may inhibit dipyridamole-induced vasodilation. It is recommended that methylxanthines such as caffeine, as well as methylxanthine-containing products such as Ilex guayusa, be stopped 24 hours prior to pharmacological stress tests. Methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing.

Likelihood Probable Evidence B

Disulfiram (Antabuse)

Theoretically, disulfiram might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. In human research, disulfiram decreases the clearance and increases the half-life of caffeine.

Likelihood Probable Evidence B

Diuretic Drugs

Theoretically, concomitant use might increase the risk of hypokalemia.
Ilex guayusa contains caffeine. Caffeine, especially in excessive amounts, can reduce potassium levels due to stimulation of the sodium-potassium pump. Diuretics can also cause lower potassium levels.

Likelihood Possible Evidence D

Estrogens

Theoretically, estrogens might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Estrogen inhibits caffeine metabolism.

Likelihood Probable Evidence B

Flutamide (Eulexin)

Theoretically, Ilex guayusa might increase the levels and adverse effects of flutamide.
Ilex guayusa contains caffeine. In vitro evidence suggests that caffeine can inhibit the metabolism of flutamide. Theoretically, concomitant use of caffeine and flutamide might increase serum concentrations of flutamide and increase the risk adverse effects.

Likelihood Possible Evidence D

Fluvoxamine (Luvox)

Theoretically, fluvoxamine might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Fluvoxamine reduces caffeine metabolism.

Likelihood Probable Evidence B

Lithium

Theoretically, abrupt Ilex guayusa withdrawal might increase the levels and adverse effects of lithium.
Ilex guayusa contains caffeine. Abrupt caffeine withdrawal can increase serum lithium levels. Two cases of lithium tremor that worsened with abrupt coffee withdrawal have been reported.

Likelihood Probable Evidence D

Monoamine Oxidase Inhibitors (Maois)

Theoretically, concomitant use might increase the risk of a hypertensive crisis.
Ilex guayusa can contain caffeine. Caffeine has been shown to inhibit monoamine oxidase (MAO) A and B in laboratory studies. Concomitant intake of large amounts of caffeine with MAOIs might precipitate a hypertensive crisis.

Likelihood Possible Evidence D

Nicotine

Theoretically, concomitant use might increase the risk of hypertension.
Ilex guayusa contains caffeine. Concomitant use of caffeine and nicotine has been shown to have additive cardiovascular effects, including increased heart rate and blood pressure. Blood pressure was increased by 10.8/12.4 mmHg when the agents were used concomitantly.

Likelihood Probable Evidence B

Pentobarbital (Nembutal)

Theoretically, Ilex guayusa might reduce the effects of pentobarbital.
Ilex guayusa contains caffeine. Theoretically, caffeine might negate the hypnotic effects of pentobarbital.

Likelihood Possible Evidence B

Phenobarbital (Luminal)

Theoretically, Ilex guayusa might reduce the effects of phenobarbital and increase the risk for convulsions.
Ilex guayusa contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of phenobarbital. The exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D

Phenylpropanolamine

Theoretically, phenylpropanolamine might increase the risk of hypertension, as well as the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Concomitant use of phenylpropanolamine and caffeine might cause an additive increase in blood pressure. Phenylpropanolamine also seems to increase caffeine serum levels.

Likelihood Probable Evidence B

Phenytoin (Dilantin)

Theoretically, Ilex guayusa might reduce the effects of phenytoin and increase the risk for convulsions.
Ilex guayusa contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of phenytoin. The effect does not seem to be related to the seizure threshold-lowering effects of caffeine. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D

Pioglitazone (Actos)

Theoretically, caffeine might increase the levels and clinical effects of pioglitazone.
Ilex guayusa contains caffeine. Animal research suggests that caffeine can modestly increase the maximum concentration, area under the curve, and half-life of pioglitazone, and also reduce its clearance. This increased the antidiabetic effects of pioglitazone. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D

Riluzole (Rilutek)

Theoretically, concomitant use might increase the levels and adverse effects of both caffeine and riluzole.
Ilex guayusa contains caffeine. Caffeine and riluzole are both metabolized by cytochrome P450 1A2 (CYP1A2), and concomitant use might reduce metabolism of one or both agents.

Likelihood Possible Evidence D

Stimulant Drugs

Theoretically, concomitant use might increase stimulant adverse effects.
Ilex guayusa contains caffeine. Due to the central nervous system (CNS) stimulant effects of caffeine, concomitant use with stimulant drugs can increase the risk of adverse effects.

Likelihood Probable Evidence C

Theophylline

Theoretically, Ilex guayusa might increase the levels and adverse effects of theophylline.
Ilex guayusa contains caffeine. Large amounts of caffeine might inhibit theophylline metabolism.

Likelihood Probable Evidence B

Valproate

Theoretically, Ilex guayusa might reduce the effects of valproate and increase the risk for convulsions.
Ilex guayusa contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of valproate. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D

Verapamil (Calan, Others)

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Verapamil increases plasma caffeine concentrations by 25%.

Likelihood Possible Evidence D

Alcohol (Ethanol)

Theoretically, alcohol might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Concomitant use of alcohol can increase caffeine serum concentrations and the risk of caffeine adverse effects. Alcohol reduces caffeine metabolism.

Likelihood Possible Evidence D

Antidiabetes Drugs

Theoretically, taking Ilex guayusa with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research in a model of hyperglycemia suggests that Ilex guayusa may have antihyperglycemic effects, although it does not appear to lower glucose levels when compared with baseline. This effect has not been evaluated in humans.

Likelihood Unlikely Evidence D

Fluconazole (Diflucan)

Theoretically, fluconazole might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Fluconazole decreases caffeine clearance by approximately 25%.

Likelihood Possible Evidence B

Metformin (Glucophage)

Theoretically, metformin might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Animal research suggests that metformin can reduce caffeine metabolism. Theoretically, concomitant use can increase caffeine serum concentrations and the risk of caffeine adverse effects.

Likelihood Possible Evidence D

Methoxsalen (Oxsoralen)

Theoretically, methoxsalen might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Methoxsalen can reduce caffeine metabolism. Concomitant use can increase caffeine serum concentrations and the risk of caffeine adverse effects.

Likelihood Possible Evidence B

Mexiletine (Mexitil)

Theoretically, mexiletine might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Mexiletine can decrease caffeine elimination by 50%.

Likelihood Possible Evidence B

Phenothiazines

Theoretically, phenothiazines might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Phenothiazines can reduce the metabolism of caffeine by inhibiting cytochrome P450 1A2 (CYP1A2).

Likelihood Possible Evidence D

Quinolone Antibiotics

Theoretically, quinolone antibiotics might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Concomitant use of quinolones can decrease caffeine clearance and increase effects and risk of adverse effects.

Likelihood Possible Evidence B

Terbinafine (Lamisil)

Theoretically, terbinafine might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. Terbinafine decreases the clearance of intravenous caffeine by 19%.

Likelihood Possible Evidence B

Tiagabine (Gabitril)

Theoretically, Ilex guayusa might increase the levels and adverse effects of tiagabine.
Ilex guayusa contains caffeine. Animal research suggests that chronic caffeine administration can increase the serum concentrations of tiagabine. However, concomitant use does not seem to reduce the antiepileptic effects of tiagabine.

Likelihood Possible Evidence D

Ticlopidine (Ticlid)

Theoretically, ticlopidine might increase the levels and adverse effects of caffeine.
Ilex guayusa contains caffeine. In vitro evidence suggests that ticlopidine can inhibit caffeine metabolism. However, this effect has not been reported in humans.

Likelihood Possible Evidence D

Monograph

Ilex Guayusa: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Ilex guayusa is a caffeine-containing holly leaf from the Amazon, traditionally brewed as a tea for energy and alertness, much like yerba mate or green tea. There is limited human research confirming specific health benefits, and its main reliable effect comes from its caffeine content. Because it is a stimulant, use it cautiously and check with your pharmacist or doctor if you have heart concerns or are pregnant.

Scientific name: Ilex guayusa
Family: Aquifoliaceae
Part used: Leaves
Common forms: Tea, brewed infusion, capsules, powdered extract, energy drinks

People commonly use it for

Energy and alertness
Mental focus
Antioxidant support
Appetite control
Athletic and physical performance

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally well tolerated in tea amounts, but it contains caffeine that can cause stimulant side effects.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Ilex guayusa is a tree in the holly family that grows in the Amazon rainforest, mainly in Ecuador. Its leaves have been used for centuries by Indigenous peoples, who brew them into a tea that is often consumed early in the morning for energy and a sense of alertness.

Guayusa is closely related to other caffeine-containing plants like yerba mate (Ilex paraguariensis) and holly. Today it is sold as loose-leaf tea, tea bags, capsules, powders, and as an ingredient in energy drinks. People are drawn to it as a natural source of caffeine that some describe as giving a smoother, less jittery feeling than coffee, though this is mostly based on personal reports rather than strong studies.

How it works

The main active ingredient is caffeine, a natural stimulant that blocks adenosine, a brain chemical that promotes sleepiness. This is why guayusa can increase alertness and reduce feelings of fatigue.

The leaves also contain other compounds such as theobromine (also found in chocolate) and antioxidant plant chemicals like chlorogenic acids and flavonoids. In laboratory and animal studies, these antioxidants can neutralize damaging molecules called free radicals. However, these mechanisms are mostly based on test-tube and animal research, and it is not clear how much they affect human health when you drink guayusa.

Effectiveness

Does Ilex Guayusa work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 2 uses evaluated

2 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Ilex Guayusa, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 2 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Cognitive function

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral Ilex guayusa is beneficial for improving cognitive performance in adults.

Insufficient Reliable Evidence To Rate Diabetes

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral Ilex guayusa for diabetes, there is insufficient reliable information about the clinical effects of Ilex guayusa for this condition.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

For most healthy adults, guayusa tea appears to be reasonably well tolerated when consumed in normal beverage amounts. The main safety concern is its caffeine content, which can add up if you also drink coffee, tea, energy drinks, or take caffeine pills.

Use extra caution if you have heart rhythm problems, high blood pressure, anxiety, sleep trouble, or are sensitive to caffeine. Children and teens should generally limit caffeine-containing products.

Pregnancy: It is best to limit or avoid guayusa during pregnancy. High caffeine intake has been linked to pregnancy risks, and there are no good safety studies on guayusa specifically. Breastfeeding: Caffeine passes into breast milk and can affect a nursing baby, so limit or avoid it until more is known. When in doubt, talk to your doctor or pharmacist.

Side effects

Most side effects are related to caffeine and may include jitteriness, a faster heartbeat, anxiety, headache, upset stomach, and trouble sleeping, especially if you drink it later in the day or in large amounts.

Drinking very large quantities could lead to more pronounced caffeine effects such as palpitations or restlessness. As with other herbal teas in the holly family, some people may experience stomach irritation. Stop using it and seek medical advice if you have chest pain, a racing or irregular heartbeat, or other concerning symptoms.

Ilex Guayusa: Reported Adverse Effects

Documented safety reports on Ilex Guayusa from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Reports by condition

Anxiety Psychiatric

Chronic use of caffeine, especially in large amounts, may produce tolerance, habituation, and psychological dependence. There is some concern that stopping regular use of caffeine may cause withdrawal symptoms such as headache, tiredness and fatigue, decreased energy, alertness, and attentiveness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and lack of clear-headedness. Other symptoms such as delirium, nervousness, restlessness, and anxiety have been described. However, these symptoms may be from nonpharmacological factors related to knowledge and expectation of effects. Certain populations such as children and the elderly may be more susceptible to the adverse effects of caffeine.

Bone loss Musculoskeletal

Epidemiological evidence regarding the relationship between caffeine, which is found in Ilex guayusa, and the risk of osteoporosis is contradictory. Caffeine can increase urinary excretion of calcium. Females identified with a genetic variant of the vitamin D receptor appear to be at an increased risk of the detrimental effect of caffeine on bone mass. However, moderate caffeine intake, less than 300 mg per day, does not seem to significantly increase osteoporosis risk in most postmenopausal adults with normal calcium intake.

Breast cancer Endocrine

Some evidence shows that caffeine, a constituent of Ilex guayusa, is associated with fibrocystic breast disease, breast cancer, and endometriosis in females; however, this is controversial since findings are conflicting. Restricting caffeine in females with fibrocystic breast conditions doesn't seem to affect breast nodularity, swelling, or pain. A population analysis of the Women's Health Initiative observational study has found no association between consumption of caffeine-containing beverages and the incidence of invasive breast cancer in models adjusted for demographic, lifestyle, and reproductive factors. Also, a dose-response analysis of 2 low-quality observational studies has found that high consumption of caffeine is not associated with an increased risk of breast cancer.

Clinical research in healthy adults shows that increased consumption of caffeine results in increased insulin resistance.

Dry mouth Gastrointestinal

Orally, dry mouth was reported by one study participant taking a single dose of guayusa extract.

La Monica MB, Raub B, Ziegenfuss EJ, et al. Acute effects of naturally occurring guayusa tea and Nordic lion's mane extracts on cognitive performance. Nutrients 2023;15(24):5018.

Hypertension Cardiovascular

Orally, a single dose of guayasa extract 600 mg or 1200 mg has been reported to increase systolic blood pressure by 4-6 mmHg and diastolic blood pressure by 2-5 mmHg on average in small clinical studies.

Although acute administration of caffeine, a constituent of Ilex guayusa, can cause increased blood pressure, regular consumption does not seem to increase either blood pressure or pulse, even in mildly hypertensive patients. Drinking one or more cups daily of caffeinated coffee also doesn't seem to increase the risk of developing hypertension in habitual coffee drinkers.

Myasthenia gravis Neurologic/CNS

Orally, jitteriness increased in females, but not males, taking a single dose of guayusa extract in a clinical trial. The level of jitteriness reported was greater in those taking 1200 mg than those taking 600 mg. In one clinical trial, a study participant reported tremors after taking a single 650 mg dose of guayusa extract.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no official standardized dose for guayusa. It is most commonly taken as a brewed tea, and the amount of caffeine you get can vary widely depending on how much leaf you use and how long you steep it.

If you use a packaged product, follow the directions on the label and do not exceed the recommended serving. Keep your total daily caffeine from all sources in mind. If you are unsure how much is safe for you, especially if you have a health condition or take medications, check with your pharmacist or doctor.

Pregnancy & Breastfeeding

Ilex Guayusa & Pregnancy

Insufficient reliable information

Insufficient reliable information available; avoid using.

Ilex Guayusa & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 90 references that drive our Ilex Guayusa monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
Harder S, Fuhr U, Staib AH, Wolff T. Ciprofloxacin-caffeine: a drug interaction established using in vivo and in vitro investigations. Am J Med 1989;87:89S-91S. PubMed
Carbo M, Segura J, De la Torre R, et al. Effect of quinolones on caffeine disposition. Clin Pharmacol Ther 1989;45:234-40. PubMed
Healy DP, Polk RE, Kanawati L, et al. Interaction between oral ciprofloxacin and caffeine in normal volunteers. Antimicrob Agents Chemother 1989;33:474-8. PubMed
Mester R, Toren P, Mizrachi I, et al. Caffeine withdrawal increases lithium blood levels. Biol Psychiatry 1995;37:348-50. PubMed
Jefferson JW. Lithium tremor and caffeine intake: two cases of drinking less and shaking more. J Clin Psychiatry 1988;49:72-3.
Joeres R, Klinker H, Heusler H, et al. Influence of mexiletine on caffeine elimination. Pharmacol Ther 1987;33:163-9. PubMed
Vahedi K, Domingo V, Amarenco P, Bousser MG. Ischemic stroke in a sportsman who consumed MaHuang extract and creatine monohydrate for bodybuilding. J Neurol Neurosurg Psychiatr 2000;68:112-3.
Wakabayashi K, Kono S, Shinchi K, et al. Habitual coffee consumption and blood pressure: A study of self-defense officials in Japan. Eur J Epidemiol 1998;14:669-73. PubMed
Hodgson JM, Puddey IB, Burke V, et al. Effects on blood pressure of drinking green and black tea. J Hypertens 1999;17:457-63. PubMed
Rapuri PB, Gallagher JC, Kinyamu HK, Ryschon KL. Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes. Am J Clin Nutr 2001;74:694-700. PubMed
Pollock BG, Wylie M, Stack JA, et al. Inhibition of caffeine metabolism by estrogen replacement therapy in postmenopausal women. J Clin Pharmacol 1999;39:936-40. PubMed
Nurminen ML, Niittynen L, Korpela R, Vapaatalo H. Coffee, caffeine and blood pressure: a critical review. Eur J Clin Nutr 1999;53:831-9. PubMed
Dews PB, Curtis GL, Hanford KJ, O'Brien CP. The frequency of caffeine withdrawal in a population-based survey and in a controlled, blinded pilot experiment. J Clin Pharmacol 1999;39:1221-32. PubMed
Boozer CN, Nasser JA, Heymsfield SB, et al. An herbal supplement containing Ma Huang-Guarana for weight loss: a randomized, double-blind trial. Int J Obes Relat Metab Disord 2001;25:316-24. PubMed
Hagg S, Spigset O, Mjorndal T, Dahlqvist R. Effect of caffeine on clozapine pharmacokinetics in healthy volunteers. Br J Clin Pharmacol 2000;49:59-63. PubMed
Lloyd T, Johnson-Rollings N, Eggli DF, et al. Bone status among postmenopausal women with different habitual caffeine intakes: a longitudinal investigation. J Am Coll Nutr 2000;19:256-61. PubMed
Sinclair CJ, Geiger JD. Caffeine use in sports. A pharmacological review. J Sports Med Phys Fitness 2000;40:71-9.
Haller CA, Benowitz NL. Adverse cardiovascular and central nervous system events associated with dietary supplements containing ephedra alkaloids. N Engl J Med 2000;343:1833-8. PubMed
Ali M, Afzal M. A potent inhibitor of thrombin stimulated platelet thromboxane formation from unprocessed tea. Prostaglandins Leukot Med 1987;27:9-13. PubMed
Ardlie NG, Glew G, Schultz BG, Schwartz CJ. Inhibition and reversal of platelet aggregation by methyl xanthines. Thromb Diath Haemorrh 1967;18:670-3. DOI
Samarrae WA, Truswell AS. Short-term effect of coffee on blood fibrinolytic activity in healthy adults. Atherosclerosis 1977;26:255-60. PubMed
Klag MJ, Wang NY, Meoni LA, et al. Coffee intake and risk of hypertension: The John Hopkins precursors study. Arch Intern Med 2002;162:657-62. DOI
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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

Pharmacist Counseling Corner

Ilex Guayusa: Common Questions

What is Ilex Guayusa used for, and does it work?

People use Ilex Guayusa for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does Ilex Guayusa interact with prescription medications?

Yes. We list 605 medications with a known interaction with Ilex Guayusa, including 8 rated major. Use the checker above to see how Ilex Guayusa interacts with a specific drug.

How are Ilex Guayusa interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Ilex Guayusa with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Ilex Guayusa interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Ilex Guayusa used for?

It is mainly used as a caffeinated tea for energy, alertness, and focus. People also promote it for antioxidant support and exercise, but those uses are not well proven.

Does guayusa contain caffeine?

Yes. Guayusa leaves naturally contain caffeine, similar to coffee, tea, and yerba mate, which is why it can boost alertness.

Is guayusa safe during pregnancy or breastfeeding?

It is best to limit or avoid it. It contains caffeine, which can be risky in pregnancy and passes into breast milk, and there are no good safety studies for guayusa specifically.

How is guayusa different from coffee?

Both contain caffeine, but guayusa is an herbal tea made from holly leaves and also contains theobromine and antioxidants. Some people feel it gives a smoother energy, but this is based mostly on personal experience rather than strong research.

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

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Ilex Guayusa Drug Interactions, Uses, Effectiveness, Safety & More

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Overview

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