WARNING: Do not suddenly stop taking this medicine. Sharp chest pain, irregular heartbeat, and, sometimes, heart attack may occur if you suddenly stop this medicine. The risk may be greater if you have certain types of heart disease. Your doctor should slowly lower your dose over several weeks if you need to stop taking this medicine. This should be done even if you only take this medicine for high blood pressure. Heart disease is common and you may not know you have it. Limit physical activity while you are lowering your dose. If new or worsened chest pain or other heart problems occur, contact your doctor right away. You may need to start taking this medicine again. Some medicines or medical conditions may interact with this medicine. INFORM YOUR DOCTOR OR PHARMACIST of all prescription and over-the-counter medicine that you are taking. DO NOT TAKE THIS MEDICINE if you are also taking mibefradil. ADDITIONAL MONITORING OF YOUR DOSE OR CONDITION may be needed if you are taking other prescription and nonprescription medicines (eg, used for infections, inflammation, aches and pains, high blood pressure, heart problems, irregular heartbeat, diabetes, prostate problems, blood thinning, thyroid problems, depression, mental or mood problems, immune system suppression, allergic reactions, asthma, high cholesterol, seizures, local anesthesia, stomach or bowel problems, migraine headaches), multivitamin products, and herbal or dietary supplements (eg, herbal teas, coenzyme Q10, garlic, ginseng, ginkgo, St. John's wort). DO NOT START OR STOP any medicine without doctor or pharmacist approval. Inform your doctor of any other medical conditions, including Wolff-Parkinson-White syndrome, Down syndrome, Raynaud syndrome, an adrenal gland tumor (pheochromocytoma), allergies, pregnancy, or breast-feeding. Tell your doctor if you have a history of other heart problems (eg, angina, congestive heart failure, slow heartbeat), liver or kidney problems, blood vessel disease, lung or breathing problems (eg, chronic bronchitis, emphysema, chronic obstructive pulmonary disease / COPD), diabetes, low blood sugar, overactive thyroid, muscle problems, or glaucoma. Tell your doctor if you smoke or drink alcohol, if you will be having surgery, if you exercise, or if you have been fasting. USE OF THIS MEDICINE IS NOT RECOMMENDED if you have asthma, uncontrolled heart failure, shock caused by serious heart problems, or very low blood pressure after a heart attack. USE OF THIS MEDICINE IS NOT RECOMMENDED if you have moderate to severe heart block, sick sinus syndrome, or a very slow heartbeat and you do not have a permanent pacemaker. Contact your doctor or pharmacist if you have any questions or concerns about taking this medicine.