Drug Interaction with Black Cohosh?

My sister is on the medication Tikosyn for her heart. Is it safe for her to take black cohosh for hot flashes with this medication?

Tikosyn is used to regulate an irregular heartbeat. It comes with the warning that when taken with other drugs, the amount of tikosyn in the body can increase, causing a different and dangerous kind of irregular heartbeat. I do not know any reason why black cohosh would cause an interaction with this drug. I do not know of any studies or incidents that show whether an interaction may or may not occur.
I recommend that your sister visit a qualified natural health practitioner who can perform a complete health assessment, recommend the most suitable diet and herbs for her individual health pcutre, and follow up on their effect.