As far as I’m aware, simethicone doesn’t interact with other drugs, so is safe to give.
According to the Dana Kimpels article: (http://www.bio.miami.edu/hare/ileus.html)
(liquid, pediatric suspension or tablets) is essential for the relief of gas pain which usually accompanies ileus. For relief of acute gas pain, 1-2 cc (20mg/ml suspension) can be given as often as every hour for three doses, then 1 cc every three to eight hours. This substance has no known drug interactions, is not absorbed through the intestinal lining and acts only on a mechanical principle: it changes the surface tension of the frothy gas bubbles in the gut, joining them into larger, easier-to-pass bubbles. Simethicone is practically inert, and is safe to give, even as a precaution, as long as it is not given long term. (Note: liquid suspensions of simethicone are relatively expensive. Less expensive versions, such as 125mg gel capsules are equally effective. A bunny can safely receive the contents of half a capsule at the rate described above.) A flatulent bunny is a happy bunny!