Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: metoprolol
BRAND NAMES: Lopressor, Toprol XL
DRUG CLASS AND MECHANISM: Metoprolol is a beta-adrenergic blocking
agent that is used for treating high blood pressure, heart pain, abnormal
rhythms of the heart, and some neurologic conditions. Examples of
beta-adrenergic blockers include propanolol (Inderal), atenolol (Tenormin), and
timolol (Blocadren). Metoprolol blocks the action of the sympathetic nervous
system, a portion of the involuntary nervous system, by blocking beta receptors
on sympathetic nerves. Since the sympathetic nervous system is responsible for
increasing the rate with which the heart beats, by blocking the action of these
nerves metoprolol reduces the heart rate and is useful in treating abnormally
rapid heart rhythms.
Metoprolol also reduces the force of contraction of heart
muscle and thereby lowers blood pressure. By reducing the heart rate and the
force of muscle contraction, metoprolol reduces the need for oxygen by heart
muscle. Since heart pain (angina pectoris) occurs when oxygen demand of the
heart muscle exceeds the supply of oxygen, metoprolol, by reducing the demand
for oxygen, is helpful in treating heart pain. The FDA approved metoprolol in
August 1978.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets: 25, 50, and 100 mg. Tablets (extended release):
25, 50, 100, and 200 mg. Injection: 1 mg/ml
STORAGE: Tablets should be stored between 15-30°C (59-86°F). They
should be protected from moisture and dispensed in tight, light-resistant
container.
PRESCRIBED FOR: Metoprolol is prescribed for patients with high blood
pressure (hypertension). It is also used to treat chest pain (angina pectoris)
related to coronary artery disease. Metoprolol is also useful in slowing and
regulating certain types of abnormally rapid heart rates (tachycardias). Other
uses for metoprolol include the prevention of
migraine headache and the
treatment of certain types of tremors (familial or hereditary essential
tremors).
DOSING: Metoprolol should be taken before meals or at bedtime. The
dose for treating hypertension is 100-450 mg daily in single or divided doses.
Angina is treated with 100-400 mg daily in two divided doses. Acute myocardial
infarction is treated with three 5 mg injections administered 2 minutes apart
followed by treatment with 50 mg oral metoprolol every 6 hours for 48 hours.
After 48 hours, patients should receive 100 mg orally twice daily for at least 3
months.
DRUG INTERACTIONS: Calcium channel blockers and digoxin (Lanoxin) can
lower of blood pressure and heart rate to dangerous levels when administered
together with metoprolol.
Metoprolol can mask the early warning symptoms of low blood sugar
(hypoglycemia) and should be used with caution in patients receiving treatment
for diabetes.
PREGNANCY: Safe use of metoprolol during
pregnancy has not been
established.
NURSING MOTHERS: Small quantities of metoprolol are excreted in
breast
milk and may potentially cause adverse effects in the infant.
SIDE EFFECTS: Metoprolol is generally well tolerated. Side effects
include abdominal cramps, diarrhea, constipation, fatigue, insomnia, nausea,
depression, dreaming, memory loss, fever, impotence, lightheadedness, slow heart
rate, low blood pressure, cold extremities, sore throat, and shortness of breath
or wheezing. Metoprolol can aggravate breathing difficulties in patients with
asthma, chronic bronchitis, or emphysema.
In patients with existing slow heart
rates (bradycardias) and heart blocks (defects in the electrical conduction of
the heart), metoprolol can cause dangerously slow heart rates, and even shock.
Metoprolol reduces the force of heart muscle contraction and can aggravate
symptoms of heart failure. In patients with coronary artery disease, abruptly
stopping metoprolol can suddenly worsen angina, and occasionally precipitate
heart attacks. If it is necessary to discontinue metoprolol, its dosage should
be reduced gradually over several weeks.
Reference: FDA Prescribing Information
Last Editorial Review: 3/4/2008
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- Beta Blockers - Learn more about Beta Blockers, a drug that treats angina and other heart rhythm disorders, migraines, high blood pressure, panic attacks, and tremors. Generic and brand names are included in the article.
- High Blood Pressure - Learn about high blood pressure symptoms like headache, dizziness, shortness of breath, blurred vision and more. Causes, and normal blood pressure information is included.
- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
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