This seems to be the first time the potential for these interactions has been studied.

Here are the details.

• 20 volunteers were assigned to 14 days of goldenseal root extract (1,323 mg, 3 times daily, standardized to 24.1 mg isoquinoline alkaloids per capsule) and kava kava rhizome extract (1,227 mg, 3 times daily, standardized to 75 mg kavalactones per capsule).
• Digoxin (Lanoxin) 0.5 mg was administered by mouth before and at the end of goldenseal and kava kava treatment and the control period.
• Digoxin blood levels were drawn and pharmacokinetic calculations were performed.

Goldenseal caused a 14% increase in the peak blood levels of digoxin. But none of the other calculations showed any change in digoxin blood levels by goldenseal or kava kava.

It seems to me that a 14% increase in digoxin blood levels, considering its narrow therapeutic range, might have a significant effect in some patients. Nevertheless, the researchers concluded, “supplementation with these specific formulations of goldenseal or kava kava did not appear to affect digoxin pharmacokinetics.”

3/24/07 19:56 JR