The short answer
Ask about passionflower before taking it with promethazine, especially if alertness is already affected. The exact pair has not been shown to cause extra sedation, and a small standalone trial found no sedation increase.
What this answer covers
Oral promethazine with the specific preparation described below.
- Supplement or preparation
- Passiflora incarnata
- Medication ingredient
- promethazine
The guidance is precautionary
The passionflower aerial-part monograph warns that driving may be affected, but lists no reported interactions. A lack of reports is not proof of safety, and the warning is not a measured promethazine interaction.
A human trial found less anxiety without added sedation
Sixty adults received a specific Passiflora incarnata preparation or placebo before surgery. Anxiety improved, but measured sedation, psychomotor recovery and discharge time did not significantly differ. That negative sedation finding should not be omitted.
The study does not establish this combination
The tested perioperative preparation does not represent every tea, capsule or extract, and the study did not estimate the effect of taking it with promethazine. No protective hours-apart schedule or universal avoidance rule was demonstrated.
Review the whole alertness burden
Bring the exact supplement label and all medicines to your pharmacist, particularly if promethazine already makes you sleepy, dizzy or confused. Avoid driving when affected. The reviewed evidence does not identify a supplement dose or hours-apart schedule that guarantees normal alertness.
Evidence and practical considerations
Side effects & toxicity
Ask about passionflower before taking it with promethazine, especially if alertness is already affected. The exact pair has not been shown to cause extra sedation, and a small standalone trial found no sedation increase.
- Exact scope
- Oral promethazine with the specific preparation described below. with Oral promethazine; the hyoscine source, where relevant, is explicitly transdermal.
- Medication form and route
- oral
What remains uncertain
- Conditional alertness review from traditional-use guidance and exact drug warning. Current exact sedation or avoidance/timing claim insufficient; original perioperative sedation-null retained, no validated dose gap.
Factors that may matter: Exact preparation and amount; Other medicines with overlapping effects; Route and gut-transit status where relevant.
Read the supporting source summaries
Source 1: Current U.S. regulatory product labeling
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral promethazine.
Promethazine can cause marked drowsiness, can intensify other CNS depressants and requires caution with other anticholinergic medicines. It can lower the seizure threshold.
How this applies: Exact active ingredient and oral-route context.
Label warnings do not measure every exact supplement pair or provide a universal safe supplement dose or interval.
Source 2: Regulatory herbal monograph
ema.europa.eu · Source check Sep 10, 2026
Population: People considering covered passionflower aerial-part preparations.
Warns that driving may be affected; lists no reported interactions.
How this applies: Supports conditional product and alertness review.
Traditional-use guidance, not a quantified exact combination or universal spacing instruction.
Source 3: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Sixty adults awaiting ambulatory surgery.
Anxiety decreased without significant differences in measured sedation, psychomotor recovery or discharge time.
How this applies: Preserves a negative sedation finding.
Selected product and short perioperative period, no exact target medication co-use estimate.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Initial source-checked research draft with exact preparation limits, contrary findings and source-access details. Clinical review not recorded. | |
| Research summary published |
Article revision: 36a65abce7c1b3d6
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.