Just a little addition to Kenneth's answer. Marijuana can also interfere with Vitamin C absorption which plays a role in the body's immunity and overall cellular health. Smoking Marijuana can definitely interfere with the body's ability to heal and stay healthy due to the aforementioned vitamin absorption issues as well as the fact that smoking anything can irritate the sinus' and the rest of the respiratory tract.
Anitbiotics kill all the good and bad bacteria in the body. The "good" bacteria (flora) in your gut actually assist in synthesizing certain vitamins (like vitamin K and some vitamin B's) thus if you are to take a round of antibiotics without supplementing with probiotics (i.e. acidopholus) and Vitamin K and B-complex, you are perpetuating the cycle of lowering the immunity and becoming sick!
1. stop smoking marijuana while sick
2. take acidopholus or other probiotic supplements
3. take VItamin K and Vitamin B complex
4. If you choose to continue using marijuana after you have fully recovered, use a vaporizer, or edibles, much easier on the body and far less irritating.
Good luck and feel better!
American College of Healthcare Sciences
Been there, done that.