Passion flower has related analgesic, sedative, sleep-inducing, and spasmolytic effects. The major pharmacological effect of passion flower, first observed nearly a hundred years ago and consistently reported ever since, is a sedative property. The analgesic property of this herb was also observed, and doctors had success treating the sleeplessness experienced by neurasthenic and hysteric patients, as well as that caused by nervous exhaustion. Early investigators noticed that the herb worked best when sleeplessness could be traced to an inflammation of the brain; passion flower appeared to act as an analgesic and was free from side effects. Later in this century, investigators discovered that the flavonoid fraction was more effective. However, other tests showed that the most effective sedative activity was obtained from a combination of both the flavonoids and the alkaloids. Early research indicated that an extract of passion flower was effective against the disturbance of menopause, and as agent against the sleeplessness that occurred during convalescence from the flu. The herb had no side effects, and appeared to induce a normal peaceful sleep. Observations on the day following administration revealed no depression of body or mind, in contrast to the morning-after effects usually experienced with narcotic drugs. Passion flower is one of the main constituents of a German sleeping pill called Vita-Dor. This product, also containing aprobarbital, valerian root, hops, mellissa, and thiamine, is highly effective in inducing and maintaining sleep throughout the night. A recent Romanian patent was issued for a sedative chewing gum that contains passion flower extract in a base of several vitamins. Many other examples of the widespread application of passion flower in Europe could be cited; however, American recognition of the sedative effects of passion flower has lagged seriously behind. Some of passion flower's main constituents are the harmine and harman alkaloids (passiflorine, aribine, loturine, yageine, etc.). In man small doses (about 3-6 mg) stimulate the central nervous system, much like coffee and tea (black). In larger doses (15-35 mg), these alkaloids produce a strong motoric restlessness followed by drowsiness. Still larger doses intensify the motoric activity and cause hallucinations, convulsions, and vomiting. Oral doses of 300-400 mg will produce marked psychotic symptoms, replete with hallucinations, followed by pronounced central nervous system depression. Hence, passion flower is sometimes used as a mild hallucinogen. Since large doses of pure harman alkaloids are needed to produce psychoactive symptoms of any merit, use of the whole plant probably has no such observable effect. Pharmacological investigations in animals indicate that relatively large doses of harman derivatives excite the central nervous system, producing hallucinations and convulsions that appear to be of extrapyramidal origin. These effects do not agree with the properties of the whole plant. Harman alkaloids arrest spasms in smooth muscle, lower the blood pressure, and expand the coronary vessels, effects which have also been observed in whole herb extracts and appear occasionally in the folk literature. A centrally-depressive chemical, a gamma-pyrone derivative called maltol, has been isolated from passion flower and shown to have mild sedative properties in mice; maltol could offset the stimulant properties of harman alkaloids, but it is unlikely that it account for all sedative effects observed in humans. Presently, the active principle in passion flower remains unknown. It has been verified that the herb's alkaloid fraction is sedative, the flavonoid fraction (also containing some harman) is active, and a combination of the two is most active.