When USP came out with the og Cissus Rx, I was having debilitating elbow tendonitis. I had actually stopped going to the gym, which is highly rare for me. So I decided to give it a shot. It was miraculous-- 100% effective, got me back in the gym.
Then a couple years later, the problem resurfaced. USP had the new Super Cissus by then, so I bought some. It helped, but not nearly as much as the original stuff. I have no idea why.
What I've learned about tendonitis is this: it's simply from overuse. You should take some time off to recover, and you must adjust your routines accordingly. For instance, I used to work back and biceps on the same day. Now I've actually split it into 3 different days: pullups/pulldowns on the same day I do shoulder presses; rowing movements on the same day I do bench presses; and biceps on my leg day. So I'm doing the same amount of work with my biceps, but it's spread over 3 days instead of 1. This helps immensely. Good luck.