Piperaceae

Piper methysticum

Kava or awa ( Piper methysticum ) is a plant that grows in the South Pacific Islands. Eight species have been identified by the local cultivators on the basis of its habitat, such as mountainous versus lowland, in shade versus in full sun. In the Pacific Islands kava has been widely consumed for hundreds of years as a traditional ceremonial beverage and for its mood-altering and stress relieving properties [ ]. Traditional preparations use aqueous emulsions of the crushed or dried roots or lower stems of the kava shrub, and its pharmacological properties have been attributed to a group of components collectively known as kava pyrones or kava lactones.

However, in recent years there has been an expanding global market for herbal formulations containing lipid kava extracts in the west, largely evolving in Germany and spreading to the American and European markets. Thus, Western formulations may contain compounds that are not present in the drink that is commonly prepared in the South Pacific and may therefore cause different adverse reactions [ ]. This may explain the risk of liver damage that has been seen in the West.

In the UK, three licensed medicines and a large number of unlicensed herbal remedies containing kava were available until they were banned in 2004. These products were marketed for the treatment of mild anxiety, for which kava seems to be effective [ ], insomnia, premenstrual syndrome, and stress, and were sold over the counter as complementary medicines or as dietary supplements and nutraceuticals.

Preparations of Piper methysticum have been withdrawn from many European and North American markets because of safety concerns, and in particular hepatotoxicity. Depending on the preparation and dose used, adverse effects have been reported in 1.5–2.3% of subjects [ ].

Kava contains the pyridine alkaloid pipermethystine, the chalcone flavokavain, the norsesquiterpenoid dihydrokavain, and the pyran tetrahydroyangonin.

The acute and chronic effects of kava were first described by the 19th-century German toxicologist Louis Lewin [ ] in his book Phantastica (1924).

A carefully prepared kava beverage taken in small quantity occasioned only slight and agreeable modifications of sensibility. In this form it is a stimulating beverage after the imbibition whereof hardships can be endured more easily. It refreshes the fatigued body and brightens and sharpens the intellectual faculties. Appetite is augmented, especially if it is taken half an hour before meals…After doses that are not too strong a state of happy carelessness, content, and well-being appears without any physical or mental excitation. It is a real euphoric state which is accompanied by an increased muscular efficiency. At the beginning speech is fluent and lively and the hearing becomes more sensible to subtle impressions. Kava has a soothing effect. Those who drink it are never choleric, angry, aggressive and noisy, as in the case of alcohol. Both natives and whites look upon it as a sedative in case of accidents. Reason and consciousness remain unaffected. After the consumption of greater quantities, however, the limbs become weary, the muscles seem out of control of the will, the gait is slow and unsteady, and the subject appears half drunk. An urgent desire to lie down manifests itself. The eye sees objects before it but is unable to identify them with exactness. In the same way the ears hear everything, but the individual is unable to account for what he hears. Everything becomes more and more diffuse. The drinker succumbs to fatigue, and experiences a desire to sleep which is stronger than all other impressions. He becomes somnolent and finally falls asleep. Many Europeans have themselves experienced this action of kava which paralyses the senses like magic and finally leads to deep sleep. Frequently a state of somnolent torpor accompanied by incoherent dreams and occasionally erotic visions remains without sleep supervening.

The sleep is similar to that produced by alcohol, out of which the individual can be awakened only with difficulty. If moderate quantities have been consumed it occurs twenty to thirty minutes later, and lasts from two to eight hours according to the degree of habituation of the subject. If the beverage is concentrated, that is contains a large amount of the resinous components of kava, intoxication comes on much more rapidly. The drinkers are found lying in the very places where they have been drinking. Occasionally a short state of nervous trembling occurs before they fall asleep. No excitation precedes these symptoms.

The kava drinker is incessantly tormented with the craving for his favourite beverage, which he cannot prepare for himself. It is a repugnant spectacle to see old and white-haired people, degenerate through prolonged abuse of the drug, going from house to house in order to beg for freshly prepared kava and often meeting with a refusal. Mental weakness has also been stated to follow from kavaism. It is said that old kava habitues have red, inflamed, bloodshot eyes, dull, bleary, and diminished in their functions. They become extremely emaciated, their hands tremble, and finally they cannot bring the drinking vessel to their mouths. Numerous cutaneous diseases of the natives of the South Seas, especially a kind of scaly eruption which results in a parchment-like state of the skin, have been attributed to the abuse of kava.

The effects of kava kava have been reviewed [ ]. The chief adverse reactions are a dermopathy and liver damage.

The efficacy and safety of kava kava have been analysed in three double-blind, randomized, placebo-controlled trials in generalized anxiety disorder in 64 adult out-patients, including one study with an active comparator (venlafaxine) [ ]. Since the study designs were comparable, the kava and placebo data were then pooled for further efficacy and safety analyses. There were no significant differences between the groups in any of the trials. In the pooled analyses, kava had no effects, while there was a significant effect in favor of placebo in participants with higher anxiety at baseline. There was no evidence of hepatotoxicity with kava.

Cardiovascular

Tachycardia and electrocardiographic abnormalities have been reported in heavy users of kava [ ]. Whether these observations represent true adverse effects or are due to other factors is unclear.

Respiratory

Shortness of breath has been reported in heavy aboriginal kava users; pulmonary hypertension has been proposed as a possible cause [ ].