Lopressor is used for:
Treating high blood pressure, alone or with other medicines; long-term treatment of chest pain; and reducing the risk of death because of heart problems in patients who have had a heart attack. It may also be used for other conditions as determined by your doctor.

Lopressor is a beta-adrenergic blocking agent ("beta-blocker"). It works by reducing the amount of work the heart has to do (reduces chest pain) and the amount of blood the heart pumps out (lowers high blood pressure). It is also used to stabilize the heart rhythm in conditions in which the heart is beating too fast or at an irregular rhythm.

Do NOT use Lopressor if:
you are allergic to any ingredient in Lopressor
you have a very slow heart rate condition (eg, bradycardia, AV block); heart failure controlled by diuretics (eg, furosemide) and digoxin; or very low systolic blood pressure (less than 100 mm Hg)
you are taking mibefradil

Contact your doctor or health care provider right away if any of these apply to you.

Before using Lopressor :
Some medical conditions may interact with Lopressor . Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
if you are pregnant, planning to become pregnant, or are breast-feeding
if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
if you have allergies to medicines, foods, or other substances
if you have tumors on your adrenal gland, have an overactive thyroid, or are scheduled to have surgery
if you have or have a history of liver, heart, or blood circulation problems
if you have diabetes mellitus, chronic obstructive pulmonary disease (COPD), bronchitis, bronchospastic disease (difficulty breathing), or a history of asthma

Some MEDICINES MAY INTERACT with Lopressor . Tell your health care provider if you are taking any other medicines, especially any of the following:
Barbiturates (eg, phenobarbital), indomethacin, or phenylpropanolamine because they may decrease Lopressor 's effectiveness
Amiodarone, cimetidine, disopyramide, flecainide, hydralazine, ketanserin, mefloquine, mibefradil, quinazolines (eg, imatinib), quinidine, birth control pills, thioamines (eg, propylthiouracil), or verapamil because serious side effects, such as very slow heart rate and very low blood pressure, may occur
Bupivacaine, disopyramide, flecainide, hydralazine, ketanserin, or lidocaine because the risk of their side effects may be increased by Lopressor
Clonidine because stopping either of these medicines suddenly can lead to a rapid increase in blood pressure

This may not be a complete list of all interactions that may occur. Ask your health care provider if Lopressor may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Lopressor :
Use Lopressor as directed by your doctor. Check the label on the medicine for exact dosing instructions.
Lopressor is usually given as an injection at your doctor's office, hospital, or clinic. If you will be using Lopressor at home, a health care provider will teach you how to use it. Be sure you understand how to use Lopressor . Follow the procedures you are taught when you use a dose. Contact your health care provider if you have any questions.
Do not use Lopressor if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.
Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.
If you miss a dose of Lopressor , use it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not use 2 doses at once.

Ask your health care provider any questions you may have about how to use Lopressor .

Important safety information:
Lopressor may cause drowsiness, dizziness, blurred vision, or lightheadedness. These effects may be worse if you take it with alcohol or certain medicines. Use Lopressor with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
Lopressor may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects.
Patients being treated for high blood pressure often feel tired or run down for a few weeks after starting treatment. Be sure to take your medicine even if you may not feel "normal" Tell your doctor if you develop any new symptoms.
If you have angina (chest pain) or have had other heart problems, do not suddenly stop taking Lopressor without first consulting your doctor. If your doctor decides you should no longer use Lopressor , you will need to stop Lopressor gradually according to your doctor's instructions.
If your doctor has instructed you to check your blood pressure and heart rate regularly, be sure to do so.
Do not take any medicines used to treat colds or congestion without first consulting with your doctor or pharmacist.
Diabetes patients - Lopressor may affect your blood sugar. Check blood sugar levels closely. Ask your doctor before you change the dose of your diabetes medicine.
Tell your doctor or dentist that you take Lopressor before you receive any medical or dental care, emergency care, or surgery.
Lab tests, including liver and kidney function, blood pressure, and complete blood cell counts, may be performed while you use Lopressor . These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
Use Lopressor with extreme caution in CHILDREN; safety and effectiveness have not been confirmed.
PREGNANCY and BREAST-FEEDING: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Lopressor while you are pregnant. Lopressor is found in breast milk. If you are or will be breast-feeding while you use Lopressor , check with your doctor. Discuss any possible risks to your baby.

Possible side effects of Lopressor :
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Blurred vision; cold hands and feet; confusion; constipation; depression; diarrhea; dizziness; dry mouth/eyes; gas; hair loss; headache; heartburn; itching; lightheadedness; mild drowsiness; muscle aches; nausea; nightmares; ringing in the ears; short-term memory loss; sleeplessness; stomach pain; unusual tiredness or weakness.
Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fainting; pounding in the chest; swelling of the arms, hands, and feet; wheezing; yellowing of the skin or eyes.