by
John Untisz, Cecelia Candelario, and Joseph Rowlands
Wilkes University, Wilke-Barre,
PA
July 2005
Piper
methysticum Forest. f., commonly referred to as kava or
kava-kava, is a member of the Piperaceae (the pepper family). P.
methysticum is
characterized as an eight to twenty foot tall shrub with large heart
shaped leaves and a woody rhizome (Dwyer & Rattray, 1990). Cultivated mostly on tropical
Pacific Islands, kava is grown for its large rootstock rhizome.
The common name is derived from the Polynesian word, “awa” meaning
bitter. Kava is believed to have the ability to bring the
indigenous people closer to the supernatural (Stevinson et al.,
2002). Also, the calming nature of kava was involved in the
restraint of aggressive individuals in Micronesian societies (Cairney
et al., 2003).
The plant yields a supplement
that was often made into a beverage via pulverization, mixed with water
and/or coconut milk, and then filtered. Today, it is served as
powder, capsule, or beverage and therapeutically serves to relieve
anxiety, stress, and restlessness (Miller & Murray, 1998).
The traditional context of this herb is social, traditional, and at
ceremonial events (Lewis & Elvin-Lewis, 2003). Historically,
this drink was used to remove curses, celebrate marriages and births,
placate gods, and cure illnesses (Dwyer & Rattray, 1990).
Rootstocks of the kava plant
contain a collection of eighteen kavapyrones (or kavalactones), which
belong to a general category of molecules known as cyclic-esters.
Six kavalactones have been largely studied in vitro and in vivo animal
models (Lewis & Elvin-Lewis, 2003; Foster & Tyler, 1999;
Rotblatt & Ziment, 2002). Ninety-five percent of the active
and most potent chemical compounds include kawain, methysticin,
5,6-dihydrokavain, dihydromethysticin, yangonin, and
desmethoxyyangonin. Kava also contains inactive compounds
including colored chalcones (flavokavins A, B, and C), minerals
(sodium, potassium, calcium, magnesium, iron, and aluminum), and amino
acids (Lewis & Elvin-Lewis, 2003; Singh & Singh, 2002; Zeping
et al., 2005). These compounds may be the cause of the mild skin
dermopathy called kavaism (Lewis & Elvin-Lewis, 2003).
Multiple animal studies have
indicated that dihydrokawain and kawain are rapidly absorbed into the
gastrointestinal tract and into the brain with peak concentration
levels that occur within ten minutes of administration followed by
rapid decay (Rotblatt & Ziment, 2002). The brain also absorbs
methysticin, dihydromethysticin, desmethoxyyangonin, and yangonin, but
more slowly, resulting in a maximum level within thirty to fifty
minutes yet with a slower decay. Collectively, these substances
block voltage-gated sodium channels that results in an anesthetic
effect of the extract (Cairney et al., 2002).
Kava has been researched
through multiple studies, which indicate that it has been beneficial
when used as a moderate anti-anxiety medication. The drug is
currently being reviewed as a possible treatment for fear and
anxiety-related disorders and has shown a dramatic elevation in mood
and positive effects on cognitive performance, such as attention,
learning, and memory (Thompson et al., 2004). It is possible that
the use of kava may replace the usage of a category of the
pharmacological synthetic drugs benzodiazepines. Benzodiazepines have
antidepressant and anti-anxiety properties, but the adverse effects of
the drugs are significant, including memory impairment, sedation, and
dependence (Starbuck, 2000). Unlike the benzodiazepines,
discontinued use of kava does not result in any withdrawal symptoms
(Gregory et al, 1981). In various clinical studies, kava
patients have been shown to improve on the Hamilton Anxiety Scale, and
the Clinical Global Impressions Scale only after one week of treatment,
with no apparent side effects (Miller & Murray, 1998). In
addition, one particular randomized, double-blind trial (seven studies
total) using fifty-eight individuals who suffer from anxiety disorders
were placed on a 100 mg, three times a day kava regiment. After
four weeks of treatment, anxiety levels were greatly reduced with no
adverse effects (Lewis & Elvin-Lewis, 2003). Although the
mechanism for the beneficial properties of kava are unclear, strong
sedation, anticonvulsive, antispasmodic, and central muscular relaxant
effects are also attributed to the plant (Miller & Murray,
1998).
According to Stevinson et al.
(2002) and Mills et al. (2003), P.
methysticum has been associated with minor skin discoloration to
severe hepatic failure. Specifically, the method of preparation
has been shown to correlate with the degree of side effect.
Anxiolytic properties have also been shown to be dose-dependent (Garret
et al., 2003). The Michael reaction between glutathione and the
kava lactones, results in the opening of the lactone ring, and
decreases the side effects of kava extracts (Whitton et al.,
2003). The minor adverse effects of kava include: yellowing and
drying of the skin, reddening of the eyes, and loss of appetite, which
are all symptoms of kavaism (Foster & Tyler, 1999; Singh &
Singh, 2002). After a few weeks of discontinued use, the skin
returns to normal. However, in nine cases severe hepatic toxicity
later resulted in hepatic failure then death associated with high
doses, 300 to 400 mg daily, of the extract (Eisenberg & Kaptchuk,
2002; Stevinson et al., 2002). In addition, high doses may cause
blurred vision and muscle coordination inhibition, which results in
staggered walking (Lewis & Elvin-Lewis, 2003; Stevinson et al.,
2002; Cairney et al., 2002).
Indigenous people use kava in
other ways, including treatments for gonorrhea, headaches, menstrual
problems, asthma, and insomnia. Kava mave have effective
antifungal properties, specifically blocking Apergillus niger, a pathogenic mold
responsible for otomycosis, which is an infection of the external ear
canal (Starbuck, 2000). Kava is also said to be effective as a
mild anesthetic, analgesic, antithrombotic, hypnotic, neuroprotective,
and it may reduce the occurrence of hot flashes in menopausal women
(Singh & Singh, 2002). Data overwhelmingly supports the use
of kava for nonpsychotic anxiety and possibly for sleeping disorders.
P. methysticum has certainly shown
several beneficial properties within the human body when taken in
proper dosages and without the influence of benzodiazepines and
alcohol. Its harmful side effects occur after large dosages and
in conjunction with other inhibitors of the peripheral nervous system
(Garret et al., 2003; Clough et al., 2003). Further research is
required to determine the exact reason(s) for hepatic toxicity after
large doses. If shown to be effective with few adverse effect,
the use of kava to treat anxiety and stress related disorders will be
further accepted.
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