Im on sprintec birth control,i just finished 5 days of azithromycin will it effect it or will i need a backup for how long?

Newer ideas on this: The current thinking is that except for the antibiotic rifampin, other commonly-used antibiotics such as azithromycin do not alter the effectiveness of birth control pills. Of course, this is presuming a person is not sick with vomiting or diarrhea, or some other condition that decreases the absorption of a swallowed pill. One can look up: http://www.ncbi.nlm.nih.gov/pubmed/12063491

No to both questions: According to professional drug references, azithromycin does not affect how sprintec works, and Sprintec would be no more likely to fail in this case than it normally would, so you should not need a backup