I have been taking effexor/venlafaxine Hcl 75 mg. a little over 6 years...was prescribed by oncologist when diagnosed with breast cancer in 2004 (DCIS - lumpectomy and radiation). I have been cancer free for these 6 years but am afraid of withdrawing from venlafaxine. (I stopped arimidex at the 5 year mark). 5 days ago I started a new prescription for ven and began feeing like I was getting shots of adrenaline, headaches, and fatigue. The pharmacy said they switched manufacturers to Teva USA. The markings on the pills are correct for 75 mg pills. Is it possible that these effects are due to manufacturers changing?