Quick answer

NIH's complementary health center lists drowsiness, dizziness and confusion as possible side effects of passionflower. In a dental surgery trial, 50% of people given passionflower reported sleepiness, against 82.5% given the sedative midazolam, and a trial before spinal anesthesia found no change in sedation. Ask your doctor first if you take sedatives or face surgery.^1,2,3

Key facts

NCCIH lists drowsiness, dizziness and confusion as possible side effects of passionflower.¹
LiverTox says side effects of oral passionflower are not common but can include dizziness, sedation, confusion and ataxia.²
In a crossover trial of passionflower before dental surgery, 50% of people reported sleepiness, against 82.5% after midazolam.³
In a trial of a syrup given 30 minutes before spinal anesthesia, the review reports no change in the patients' sedation level.³
NCCIH says passionflower might slow the nervous system too much alongside anesthesia and advises talking to a health care provider if it is taken within 2 weeks of a scheduled surgery.¹

What NIH's complementary health center says

Possible side effects include drowsiness, dizziness and confusion.¹

NCCIH also says passionflower has traditionally been used as a sedative, and that it has not been studied extensively. Its fact sheet gives no rate for drowsiness and does not say how long it lasts.¹

Taken around the time of surgery, passionflower might slow the nervous system too much when combined with anesthesia or other medicines used before and after surgery. NCCIH advises talking to your health care provider if you take it within 2 weeks of a scheduled surgery.¹

What NIH's liver database adds

LiverTox, which covers passionflower because of the question of liver injury, also describes oral side effects. It says they are not common but can include dizziness, sedation, confusion and ataxia, which is unsteadiness in movement. It rates passionflower an unlikely cause of liver injury and says no adequately sized, placebo-controlled trial has tracked adverse events carefully.²

What trials report about sleepiness

A 2020 systematic review of nine passionflower trials, mostly in healthy adults and often before surgery or dental work, found sleepiness reported in some. In one crossover trial, people having teeth removed took either one passionflower tablet or midazolam 30 minutes beforehand, and 50% reported somnolence with passionflower, against 82.5% with midazolam.³

The same review describes a trial of a passionflower syrup given 30 minutes before spinal anesthesia, in which the patients' sedation level, psychomotor tests and hemodynamic measures did not change. In a trial of evening tea, people drank it in the evening, partly to avoid sedation during the day.³

A 30-day trial of 600 mg of extract at bedtime reported no adverse effects. It was industry funded.⁴

The trials were small, short and not built mainly to measure drowsiness, so none gives a dependable rate.³

A published case of a stronger reaction

In one published case, a woman developed severe nausea, vomiting, drowsiness and an abnormal heart rhythm after taking passionflower at usual doses, and needed hospital monitoring.⁵

One case report cannot show how often this happens, and its abstract does not say whether she had taken anything else. It is listed here because drowsiness was part of it.⁵

Taking it with other things that cause drowsiness

NCCIH says people who take any type of medicine should talk with their health care provider before using passionflower, because some herbs and medicines interact in harmful ways. Apart from anesthesia and the medicines used around surgery, no official source we could find names a specific medicine. Because drowsiness is a listed effect, a pharmacist can say whether it matters for a person who takes sedatives or sleep medicines.¹

The sources give no guidance on driving or operating machinery. A pharmacist or doctor can say whether it matters for a particular person.¹

Who should ask a doctor or pharmacist first

Anyone who takes sedatives, sleep medicines or other medicines that cause drowsiness.¹
Anyone with surgery scheduled within 2 weeks. NCCIH says to avoid passionflower before surgery unless a health care provider recommends it.¹
Anyone who notices drowsiness, dizziness or confusion after taking it. These are the effects NCCIH lists.¹
Anyone who is pregnant. NCCIH says passionflower should not be used during pregnancy.¹

Questions people ask

Does passionflower tea make you sleepy?

NCCIH lists drowsiness among possible side effects. In a trial of evening tea, people drank it in the evening, partly to avoid sleepiness during the day. No trial compared tea with capsules for drowsiness.^1,3

Can passionflower cause dizziness?

Yes, both NIH sources list it. NCCIH names dizziness among possible side effects, and LiverTox says oral side effects are not common but can include dizziness, sedation, confusion and ataxia.^1,2

Does passionflower cause confusion?

NCCIH lists confusion among possible side effects, and LiverTox lists confusion and ataxia, which is unsteadiness. Neither gives a rate. Ask your doctor if confusion follows a dose.^1,2

Should passionflower be stopped before surgery?

NCCIH says to avoid passionflower before surgery unless a health care provider recommends it, and to talk to your health care provider if you take it within 2 weeks of a scheduled surgery. Ask your doctor or surgical team.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.