You should not take carvedilol if you have asthma, bronchitis, emphysema, severe liver disease, or a serious heart condition such as heart block, "sick sinus syndrome," or slow heart rate (unless you have a pacemaker).
Avoid drinking alcohol within 2 hours before or after taking extended-release carvedilol (Coreg CR). Also avoid taking medicines or other products that might contain alcohol. Alcohol may cause the carvedilol in Coreg CR to be released too quickly into the body.
If you are being treated for high blood pressure, keep using carvedilol even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.
Before taking this medicine
You should not take carvedilol if you are allergic to it, or if you have:
asthma, bronchitis, emphysema;
severe liver disease; or
a serious heart condition such as heart block, "sick sinus syndrome," or slow heart rate (unless you have a pacemaker).
To make sure carvedilol is safe for you, tell your doctor if you have:
diabetes (taking carvedilol can make it harder for you to tell when you have low blood sugar);
angina (chest pain);
liver or kidney disease;
a thyroid disorder;
pheochromocytoma (tumor of the adrenal gland);
circulation problems (such as Raynaud's syndrome); or
a history of allergies.
FDA pregnancy category C. It is not known whether carvedilol will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.
It is not known whether carvedilol passes into breast milk or if it could harm a nursing baby. You should not breast-feed while you are taking carvedilol.
 Carvedilol pregnancy and breastfeeding warnings (more detail)
