I have been on birth control for 10 years. Right now I'm taking Yasmin. My GI doctor is recommending me to take erythromycin long-term (maybe a month or two) for treatment of chronic constipation. I'm concerned about the erythromycin decreasing the effectiveness of the pill. I've been reading all kinds of different opinions, some pages say that antibiotics (except rifampin) don't really change the effectiveness, while some pages say to use a back-up method. Can anyone give me opinions/first hand experiences with the pill and antibiotics? As far as back-up birth control, any recommendations (besides condoms)?