Hey as Tiazac (diltiazem hydrochloride) is a calcium ion cellular influx inhibitor and here I am giving you its details

Uses
Diltiazem is used to treat hypertension (high blood pressure), angina (chest pain), and certain heart rhythm disorders.
Diltiazem may also be used for purposes not listed in this medication guide.

Side effects
A red, blistering skin rash;
Swelling in your hands or feet;
Trouble breathing;
Slow heartbeats;
Dizziness, fainting, fast or pounding heartbeat;
Upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

Diltiazem extended release tablets should not be taken by anyone who:
Is allergic to diltiazem or to any of the ingredients of the medication
Is or may become pregnant
Has certain types of heart rhythm problems and does not use a pacemaker
Has fluid in the lungs due to severe heart failure
Has very low blood pressure