The short answer
Caffeine in yerba mate leaf products may increase clozapine levels. Review changes in the amount, strength or preparation with your pharmacist or clozapine prescriber.
What this answer covers
Oral caffeine-containing Ilex paraguariensis leaf preparations. Other Ilex species, non-leaf material and decaffeinated products are distinct. Roasted leaf is not equated with the non-roasted preparation covered by the HMPC monograph.
- Supplement or preparation
- Ilex paraguariensis
- Medication ingredient
- clozapine
Which product matters
The EMA report identifies caffeine in Ilex paraguariensis leaves and describes variation with processing and plant material. Other Ilex species are not equivalent. Different leaf preparations cannot be assigned one standard caffeine dose.
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 Ilex paraguariensis leaf preparations. Other Ilex species, non-leaf material and decaffeinated products are distinct. Roasted leaf is not equated with the non-roasted preparation covered by the HMPC monograph. 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.
Leaf caffeine content varies with the botanical material and processing. The assessment distinguishes non-roasted leaf from roasted leaf and identifies other Ilex species as potential adulterants.
How this applies: Establishes botanical constituent/preparation scope only. It does not establish an exact botanical-clozapine interaction.
Used for exact leaf constituent identity, not endorsement of all preparations. Roasted material is excluded from the HMPC monograph; the report does not establish its equivalence or clozapine co-use safety.
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: 434b2ef5d52a17c6
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.