I've been taking Venlafaxine XR, 225 mg, for over 10 years. I have found the only generic I can tolerate is manufactured by Greenstone. My insurance has just changed and they are telling me Greenstone's venlafaxine is on backorder and we don't know how long. What should I do? FYI, Brand Necessary would cost $1015.00 for 90 days.