The short answer
Guarana seed can supply caffeine and may increase clozapine levels. Ask your pharmacist to review the caffeine amount before starting, stopping or changing a guarana product. The evidence concerns slower clozapine metabolism, not demonstrated increased absorption.
What this answer covers
Oral caffeine-containing Paullinia cupana seed preparations, including the var. sorbilis material in the final EMA assessment. Whole plant, other parts and caffeine-free formulations are not assigned seed-equivalent exposure.
- Supplement or preparation
- Paullinia cupana
- Medication ingredient
- clozapine
Which product matters
The final EMA assessment concerns dried and powdered guarana seed, not every part of Paullinia cupana. It identifies caffeine in this material. A standard for dried seed cannot tell you the caffeine dose in an untested extract or multi-ingredient product.
Why caffeine matters with clozapine
Caffeine can slow the breakdown of clozapine. A small healthy-volunteer study found increased clozapine exposure, and a small patient study found higher concentrations during caffeinated coffee use. Neither study tested this botanical. These results justify checking caffeine exposure without predicting the same effect for everyone.
Plan changes with your care team
Give your pharmacist the full product label, serving size and frequency, together with your coffee, tea, energy drinks and other supplements. Keep intake reasonably consistent until your prescriber advises how to change it. The prescriber may monitor symptoms or clozapine levels and adjust treatment if needed. Do not change the clozapine dose yourself.
Dose changes and symptoms
Taking this supplement a few hours apart from clozapine has not been shown to prevent the caffeine interaction. Any clozapine dose adjustment should be based on your prescriber's assessment, not a general rule for another medicine. Contact your care team promptly if a product change is followed by new or worsening side effects.
Evidence and practical considerations
Absorption & effectiveness
When this oral botanical preparation supplies caffeine, it may inhibit clozapine metabolism and increase clozapine exposure. The magnitude depends on actual caffeine intake and individual response.
- Exact scope
- Oral caffeine-containing Paullinia cupana seed preparations, including the var. sorbilis material in the final EMA assessment. Whole plant, other parts and caffeine-free formulations are not assigned seed-equivalent exposure. with clozapine, RxCUI 2626 IN, oral treatment.
- Medication form and route
- Oral clozapine with oral caffeine-containing botanical preparation
What remains uncertain
- Evidence is indirect for this botanical. The studies used caffeine or coffee, not this exact preparation. The effect size, safe caffeine threshold and frequency of clinical toxicity cannot be predicted for an individual product. This does not establish increased absorption, a fixed dose reduction or an effective hour-based separation rule.
Factors that may matter: Actual caffeine per serving; Total caffeine from all sources; Starting, stopping or changing intake; Individual response.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed clozapine.
Advises monitoring for adverse reactions and considering a clinician-directed clozapine reduction if needed. The one-third dose rule is specified for strong CYP1A2 inhibitors, not caffeine.
How this applies: Exact clozapine guidance for caffeine. Applied to this botanical only when the oral preparation supplies caffeine; the label does not name this botanical.
Label does not provide a fixed caffeine dose, a universal coffee amount, or an hour-based separation instruction.
Source 2: randomized crossover pharmacokinetic study
ebi.ac.uk · Source check Sep 10, 2026
Population: 12 healthy nonsmoking men.
Clozapine AUC rose 19% and clearance fell 14%; both reported P=.05.
How this applies: Direct caffeine-clozapine evidence, indirect for this botanical. Supports a constituent-based metabolism or clearance precaution only when the product contributes relevant caffeine exposure; does not establish absorption or a botanical-specific risk magnitude.
Single-dose healthy-volunteer study, not maintenance clozapine patients; abstract-only access after failed full-text request.
Source 3: coffee-phase patient study
ebi.ac.uk · Source check Sep 10, 2026
Population: 12 hospitalized patients entered coffee and decaffeinated-coffee seven-day phases; two were excluded. Six fully compliant participants had a separate analysis.
Six fully compliant participants had 26% higher clozapine trough concentrations, not statistically significant (95% CI -3% to 54%, P=.07). Combined data showed 20% higher concentrations (95% CI 3% to 37%, P=.03).
How this applies: Direct caffeine-clozapine evidence, indirect for this botanical. Supports a constituent-based metabolism or clearance precaution only when the product contributes relevant caffeine exposure; does not establish absorption or a botanical-specific risk magnitude.
Do not merge the compliant-subgroup and combined estimates or state that all 12 were analyzed; abstract does not establish a universal caffeine dose threshold.
Source 4: Regulatory botanical assessment
ema.europa.eu · Source check Sep 10, 2026
Population: Botanical materials and preparations; not clozapine-treated participants.
The assessment identifies caffeine in guarana seed, discusses a pharmacopoeial minimum for the defined dried material, and reports constituent variability.
How this applies: Establishes botanical constituent/preparation scope only. It does not establish an exact botanical-clozapine interaction.
Seed preparation evidence is not whole-plant evidence. Pharmacopoeial specifications do not certify a commercial product or establish its actual caffeine serving. No clozapine coadministration study is provided.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Clarified practical advice about timing and clinician-directed dose changes. | |
| Research summary published |
Article revision: f918cb67c3b27413
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.