I am not sure why finasteride/propecia/proscar works antagonistically with Deca, but from my research, DHT conversion inhibition is attatcked in the same way by proscar/propecia, saw palmetto, or avodart. In other words if one is bad with Deca, they are all bad with Deca. Why would avodart be good to go with Deca and not Propecia/Proscar ? Propecia/Proscar = finisteride, Avodart = dutasteride; they work in the same manner, it's just that Avodart blocks both types of DHT conversion inhibitors, where Propecia/Proscar blocks only one. The jury is still out on how effective saw palmetto is on DHT conversion inhibition. I have been taking it for 4 years now, just in case it works, 1. Can't be bad. 2. Good for prostate.