Oh, definitely take them! You don't want to be in excrutiating pain at any time, or risk an asthma attack. You should stop taking supplements and vitamins for the duration of the cleanse, but not prescribed meds.
Interestingly, I had severe rheumatoid arthritis and asthma too, before I started my first master cleanse. I stopped taking my prednisone when I started The Master Cleanse because I decided that I couldn't live like that anymore. I am not suggesting that you do the same, by any means. Just telling you that there is hope. The pain that I suffered was debilitating - I literally could not get out of bed without medication. Now I take no medications for anything. I do have a bit of joint ache or stiffness still, sometimes, but am confident that that too will go away in time. I had total relief from the arthritis after a 15 day master cleanse and several liver flushes. I swear by the forums here - they're life savers! Cleansing and flushing will eventually restore your health if you are diligent about it.