I have it and my pain dr thinks it is from the tamoxifen

I had extreme muscle and joint pain about 6 months into herceptin treatment only. It was so severe I could barely walk and couldn't write ... I saw a specialist and basically I developed a condition they believe called Anthralgia , essentially a side effect of both chemo and herceptin. I also developed trigger finger. The good news is it is starting to go away... Instead of feeling like I'm a 90 year old with arthritis I'm now feeling like I'm closer to 50 ( true age 46) so it's getting so much better. I will continue to take herceptin until February 2015 and hoping it's completely gone after herceptin. For now an occasional pain pill ( Percocet and 600mg of ibuprofen) helps out

I'm wondering the same thing. I'm on herceptin and I feel like my body had major arthritis. Try to exercise but just makes it hurt more.

Approximately six months from last herceptin and still taking tomoxifen and feeling much better. I don't experience the joint and muscle pain much anymore.

Thanks for sharing, I guess I just need to grin and bear it.