Herbal medicine
Kava is chewed by some to relieve symptoms of throat pain, as Kava produces a “numbing” effect on the tongue and throat. The Kava is first chewed in the back of the mouth for 5 to 10 minutes while swallowing the saliva and kavalactones released from the process. The Kava produces an effect similar to that of a chloraseptic spray (An over-the-counter medicine to alleviate sore throat by numbing it, via pump-sprayed into the mouth).
Pills
Pharmaceutical companies and herbal supplement companies extract kavalactones from the kava plant using solvents such as acetone and ethanol and produce pills standardized with between 30% and 90% kavalactones. Some kava herbal supplements have been accused of contributing to very rare but severe hepatotoxic reactions such may have been due to the use of plant parts other than the root, such as stems or peelings that are known to have been exported to European manufacturers. A kava pill usually has anywhere from 60 mg to 150 mg of kavalactones. By comparison the typical bowl of traditionally prepared kava beverage has around 250 mg of kavalactones.
Pharmacology
Kava’s active principal ingredients are the kavalactones, of which at least 15 have been identified and are all considered psychoactive. Only six of them produce noticeable effects, and their concentrations in kava plants vary. Different ratios can produce different effects. The general structure of the kavalactones, without the R1-R2 -O-CH2-O- bridge and with all possible C=C double bonds shown.
Pharmacodynamics
Effects of kavalactones include mild sedation, a slight numbing of the gums and mouth, and vivid dreams. Kava has been reported to improve cognitive performance and promote a cheerful mood. Kava has similar effects to benzodiazepine medications, including muscle relaxant, anaesthetic, anticonvulsive and anxiolytic effects. They are thought to result from direct interactions of kavalactones with voltage-gated ion channels.
Research currently suggests that kavalactones potentiate GABAA activity but do not alter levels of dopamine and serotonin in the CNS. Heavy, long-term kava use does not cause any reduction of ability in saccade and cognitive tests but is associated with elevated liver enzymes.
Desmethoxyyangonin, one of the six major kavalactones, is a reversible MAO-B inhibitor (Ki 280 nM) and is able to increase dopamine levels in the nucleus accumbens. This finding might correspond to the slightly euphoric action of kava.
Kavain, in both enantiomeric forms, inhibits the reuptake of noradrenalin at the transporter (NAT), but not of serotonin (SERT). An elevated extracellular noradrenalin level in the brain may account for the reported enhancement of attention and focus.
Effects
Medical literature sometimes claims Kava has a “potential for addiction” because “it produces mild euphoria and relaxation” In a traditional setting, a moderately potent kava drink causes effects within 20–30 minutes that last for about two and a half hours, but can be felt for up to eight hours. Some report longer term effects up to two days after ingestion, including a feeling of mental clarity, patience, and an ease of acceptance. The effects of kava are most often compared to alcohol, or diazepam.
The sensations, in order of appearance, are slight tongue and lip numbing (the lips and skin surrounding may appear unusually pale); mildly talkative and sociable behavior; clear thinking; calmness; relaxed muscles; and a sense of well-being. As with other drugs that affect the GABA receptors, there can also be paradoxical dysphoria.
The numbing of the mouth is caused by the two kavalactones kavain and dihydrokavain which cause the contraction of the blood vessels in these areas acting as a local topical anesthetic. These anesthetics can also make one’s stomach feel numb. Sometimes this feeling has been mistaken for nausea. Some report that caffeine, consumed moderately in conjunction with kava can significantly increase mental alertness.
The effects of a kava drink vary widely with the particular selection of kava plant(s) and amount. A potent drink results in a faster onset with a lack of stimulation; the user’s eyes become sensitive to light, the person soon becomes somnolent and then has deep, dreamless sleep within 30 minutes. Sleep is often restful and there are pronounced periods of sleepiness correlating to the amount and potency of kava consumed.
After wakening the drinker usually does not experience any mental or physical after effects. However, this sleep has been reported as extremely restful and the user often wakes up more stimulated than he or she normally would (though excessive consumption of exceptionally potent brew has been known to cause pronounced sleepiness into the next day). Although heavy doses can cause deep dreamless sleep, it is reported that many people experience lighter sleep and rather vivid dreams after drinking moderate amounts of kava.
Adverse effects
Australian studies focused on populations with heavy concomitant consumption of alcohol and overall poor health. In one study, heavy kava use in an Aboriginal community in Arnhem Land was associated with overall poor health, a puffy face, scaly rash, and a slight increase in patellar reflexes.
There are also several documented adverse interactions with drugs, both prescription and non-prescription – including, but not limited to, Anticonvulsants, Alcohol, Anti-Anxiety Medications (CNS depressants such as benzodiazepines), Antipsychotic Medications, Levodopa, Diuretics, and Drugs metabolized by the liver.
Detection in biological fluids
Recent usage of kava has been documented in forensic investigations by quantitation of kavain in blood specimens. The principal urinary metabolite, conjugated 4′-OH-kavain, is generally detectable for up to 48 hours.
