Toprol is a Beta Blocker. Beta Blockers have several effects and can be used for different conditions. I was on Toprol XL (time release) for several years to suppress heart arrhythmias (primarily Premature Contractions and Atrial Fibrilation) and to keep my Heart Rate from going too high. One of the side effects is to also lower blood pressure but that is not it's primary purpose.
You should have received an information sheet with each prescription. A more detailed information sheet comes with the original bottles and most pharmacists will give you a copy if you ask. Pharmacists often seem to know more about drug actions, interactions, and side effects than the Doctors.
Many drug stores carry books on prescription drugs (paperbacks are much cheaper than hardbacks!). Or, simply do an Internet Search for the Drug Name.
'AL Capshaw'