Safety and effectiveness have not been established for any dose. Standard or well-studied doses of passion flower are currently lacking. Different preparations and doses have been used traditionally. Doses of 0.5-2 grams of dried herb have been taken 3-4 times daily by mouth. Doses of 1-4 milliliters of tincture (1:8) have been taken 3-4 times daily by mouth. Tea made from dried herb (four to eight grams) has been taken daily. A dose of 2.5 grams in an infusion has been used 3-4 times daily.
Children (younger than 18 years)
There is not enough scientific data to recommend passion flower for use in children at any dose.
Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.
Few reports of allergic reactions, asthma, irritated sinuses, skin rashes, and skin blood vessel inflammation (vasculitis) have been reported in the available literature with the use of passion flower products. It is believed that some reactions may have been caused by impurities in combination products, not by passion flower itself.
Side Effects and Warnings
Passion flower is generally considered to be a safe herb with few reported serious side effects. In cases of side effects, the products being used have rarely been tested for contamination, which may have been the cause. Cyanide poisoning has been associated with passiflora fruit, but this has not been proven in human studies.
Rapid heart rhythm, nausea, and vomiting have been reported. Side effects may also include drowsiness/sedation and mental slowing. Patients should use caution if driving or operating heavy machinery.
Passion flower may theoretically increase the risk of bleeding and affect blood tests that measure blood clotting (international normalized ratio or "INR").
There is a case report of liver failure and death of a patient taking a preparation of passion flower with kava. Use cautiously with any kava-containing products, as kava has been associated with liver damage. It has been suggested that the cause of the liver damage is less likely related to the presence of passion flower.
Pregnancy and Breastfeeding
There is not enough scientific evidence to recommend the safe use of passion flower in any dose during pregnancy or breastfeeding. During the 1930s, animal studies found uterine stimulant action in components of Passiflora.
Many tinctures contain high levels of alcohol and should be avoided during pregnancy.