A few years back, I wanted to delay my bleeding by a week. I was on birth control, so I took an extra week of pills and it worked great. I was left with a partial pack (1 week taken, 2 weeks of active pills still there), and over the years I've made sure to swap the partial pack back in every few months, and move some fresh pills out of circulation, so that my partial pack remains "current" (i.e., not expired), in case I need it again sometime. Hope that explanation makes sense.
Anyway, so my pill provider doesn't carry my previous brand (Levora) anymore, and they now give me Chateal instead. I'm coming up on the expiration date of the current partial pack, which is still Levora. Do you think it will be a problem to take one week of one of my fresh Chateal packs, then follow it with two weeks of Levora? For what it's worth, they do have the same active ingredients (0.15 mg levonorgestrel, 0.03 mg ethinyl estradiol). I haven't noticed any difference between them whatsoever in how they affect my mood, etc. Guess I would just be a little worried if they didn't do their job as far as preventing pregnancy...but I'm probably over-thinking this.