Celina,
Here's a link to an article which cites a study in which it was discovered that the half-life of Herceptin is longer than originally thought; I've included the quote from the article:
"The half life is now estimated to be approximately 25 days, rather than 5-6 days. Thus Herceptin may persist in the circulation for up to 18 weeks (range 15-22 weeks) after stopping Herceptin treatment," according to an EMEA statement..."
http://www.annieappleseedproject.org/wait22weekbe.html
The purpose of the article is to alert the public to the risk of taking anthracyclines too soon after discontinuing Herceptin, but I thought the info about Herceptin staying in the system for over 3 weeks would be helpful to you.
Love, Lolly