Although most antibiotics probably do not affect hormonal birth control such as pills, patch, or ring, some antibiotics may decrease their effectiveness.

By reducing the number of bacteria in intestines antibiotics might decrease the effectiveness of soy.

Certain antibiotic may stimulate further verotoxin production and thereby increase the risk of HUS However there is also tentative evidence that some antibiotics like quinolones may decrease the risk of haemolytic uraemic syndrome.

Appropriate antibiotics decrease the average 3-5 day duration of symptoms by about one day, and also reduce contagiousness.

Some antibiotics might decrease how quickly the body breaks down caffeine.

The evidence that preventative antibiotics decrease urinary tract infections in children is poor.