in addition to the "avoid side effects," like nausea and upset stomach as posted by others, there are two other case when it is better to take a drug in an empty stomach, and they are: a) a few drugs that are absorb by the stomach mucosa directly, and thus better absorb in an empty stomach, and b) other drugs can be inactivated by too much stomach acid -whose production is stimulated by ingesting food- and so it has to be taken in an empty stomach (this are older drug formulation that have been replaced by modern pharmacological formulations. Spiro does not fit either category, so it can be taken in an empty stomach.
Peky
I am not a doctor, i just stayed at the Holiday Inn Express