Antibiotics and birth control

Hi All, I know antibiotics can interfere with birth control and make it less effective and even fail. But I am just wondering which antibiotics exactly do this and to what extent? Is it inhaled such as Tobi (taken every other month) or the pill antibiotics such as azithromycin ( I take 3 times a week)? I always want to be safe in preventing pregnancy but this worries me. Thanks for your feed back!
Source: Cystic Fibrosis Pregnancy Forum - Category: Respiratory Medicine Authors: Tags: Pregnancy Source Type: forums