Interfering with how the medicine is digested and absorbed by the body. For example, milk blocks iron absorption in the stomach. Calcium found in dairy products can bind some medications, such as iron supplements and some antibiotics (Cipro and Levaquin, a quinolone.)
Pros of elongated: much more comfortable for adults. I would definitely choose it for the master bathroom. Pros of round: easier for very young children to use due to the smaller opening in the seat. Also, there are code requirements of how much foot space you need in front of a toilet.
Most people find elongated toilet bowls to be more comfortable, but in a small bathroom, a round bowl can save space. Elongated toilet bowls measure up to 31 from the wall, while round fixtures max out at 28.