From Google Scholar:
Herbals and Breastfeeding
http://www.msp.mb.ca/wp-content/uploads/2014/03/Herbals_and_Breastfeeding.pdf
"Kava Kava: Kava kava is a popular herbal medication used for nervous anxiety and restlessness. It acts by depressing the central nervous system. The drug consists of kava pyrones, called kawain, extracted from the dried rhizomes of the Piper methysticum plant. Kava kava is available in galenical preparations as well as in comminuted decoctions. Equivalent doses are based on the kava pyrone amount and are 60–120 mg daily for adults.
Kava kava is believed to enter breast milk and therefore, due to its depressant effects on the central nervous system,
it is contraindicated in nursing mothers. In addition, long-term exposure to Kava kava can cause a temporary, yellow discoloration of skin, hair, and nails. [10]"
Is Kava (Piper Methysticum) Safe and Effective for Reducing Anxiety in Adult Patients 18-65? [Systematic Review]
http://digitalcommons.pcom.edu/cgi/viewcontent.cgi?article=1083&context=pa_systematic_reviews
[Mrnjavac, Tamara, "Is Kava (Piper Methysticum) Safe and Effective for Reducing Anxiety in Adult Patients 18-65?" (2012).PCOM
Physician Assistant Studies Student Scholarship.Paper 83.]
"Key words used to locate the literature consisted of Kava (piper methysticum) and anxiety. All articles were published in English and published in peer-reviewed journals. The articles were researched by the author and obtained via OVID, PubMed, CINAHL, and COCHRANE databases. Articles were selected based on relevance and significance of outcomes to the patients (POEMS). Inclusion criteria consisted of double blind, RCT studies, included patient oriented outcomes, and were published after 1996. Exclusion criteria included: patients under 18 years old, recent anxiety/depression treatment or disorder, substance abuse, breastfeeding, pregnancy, history of liver disease, lifetime history of bipolar disorder, psychiatric disorder, organic brain syndrome, or mental retardation."
"
Presently, it is contraindicated in pregnancy and lactation, as well as Parkinson’s disease due to it’s potential dopamine antagonistic effects." [10]
[10]:Kava kava. LexiComp Online Web site.
http://online.lexi.com/crlsql/servlet/crlonline. Published 2011. Updated 2011. Accessed December 01, 2011.
Breastfeeding and Medications: Public Health Implications Frank J. Nice, DPA, CPHP Derwood, MD 20855
ftp://184.168.73.58/phscof-events/docs/2013Presentations/Thursday/Pharmacy/PharmNice.pdf
Kava hepatotoxicity solution: A six-point plan for new kava standardization-
R. Teschke et al. / Phytomedicine 18 (2011)
"In Western countries such as Germany, a set of quality specifications for kava drugs has been developed as regulatory standards in the years before the ban was issued. The standards have been compiled by experts of the Germany regulatory agency in the German kava monograph (Commission E 1990) and were supplemented later on in the official German drug codex (DAC 1998). To summarize these previous standards, the ingredients of the kava extracts had to be derived from the peeled and dried rhizome (i.e. not exposed to light) of the kava plant, maximum daily use was 120mg kavalactones for no longer than 3 months, and indications for kava extracts were anxiety, tension, and restlessness.
Pregnancy, breastfeeding, and endogen depression
were listed as contraindications."