I stopped prempro 2 weeks ago and started to take Black Cohosh 540mg 4 days ago. Am now having terrible headaches but can't find anything that says this is a side effect. Anyway I'm thinking about taking Estroven because I have read alot of good things about it and it has only 40mg of Cohosh in it. Anybody else taking this. BTW I am on my 6 year of hot flashes & night sweats. Don't know if they are ever going to go away without being on something. Ugh!!