Kava extract has been shown to potently inhibit a wide range of hepatic enzymes, suggesting a very high potential for interactions with many pharmaceuticals and herbal medications. For this reason, kava should never be consumed without the permission of your primary care physician, psychiatrist, and/or any other doctor who is prescribing medication for you. It is also recommended that you discuss your kava use with your pharmacist. Inform your anesthesiologist of your kava use well in advance of any surgery, you may be instructed to temporarily discontinue your kava use for a set period of time before and after the surgery.
Several kavalactones (e.g. Flavokavain B, Methysticin and Yangonin) have been reported to be toxic and/or carcinogenic, although further research into these mechanisms is needed and it is not yet known if kava consumption induces toxic/carcinogenic effects in vivo. Despite this, hepatoxicity has been reported in a small portion of previously healthy kava users.
Numerous kavalactones have apoptotic effects on various human tissues, which may be involved in some of the purported toxic effects of kava use.
^Tang, J; Dunlop, RA; Rowe, A; Rodgers, KJ; Ramzan, I (2010). "Kavalactones Yangonin and Methysticin Induce Apoptosis in Human Hepatocytes (HepG2) In Vitro.". Phytotherapy research : PTR25 (3): n/a. doi:10.1002/ptr.3283. PMID20734326.
^Zi X, Simoneau AR. "Flavokawain A, a novel chalcone from kava extract, induces apoptosis in bladder cancer cells by involvement of Bax protein-dependent and mitochondria-dependent apoptotic pathway and suppresses tumor growth in mice.". Cancer Research. PMID15833884.