Metoprolol

Brand names

• Apo-Metoprolol
• Betaloc
• Co-Betaloc [CD]
• Dom-Metoprolol
• Gen-Metoprolol
• Lopressor
• Lopressor HCT [CD]
• Lopressor OROS
• Novo-Metoprol
• Nu-Metop
• PMS-Metoprolol
• Toprol XL

Usage

To treat mild to moderate high blood pressure or angina; also used to prevent or control heartbeat irregularities (cardiac arrhythmias). Injection is used in hospitals for emergency treatment of heart attack, followed by maintenance with oral forms.

How it works

Metoprolol slows the rate and force of contraction of the heart by blocking certain nerve impulses, thus reducing blood pressure. By modifying nerve impulses to the heart, the medicament also helps to stabilize heart rhythm.

Side effects

Serious

Shortness of breath, wheezing; irregular or slow heartbeat (50 beats per minute or less); chest pain or tightness; swelling of the ankles, feet, and lower legs; mental depression. If you experience such symptoms, stop taking metoprolol and get medical help right away.

Common

Dizziness or lightheadedness, especially when rising suddenly to a standing position; decreased sexual ability; unusual fatigue, weakness, or drowsiness; insomnia.

Less common

Anxiety, irritability, nervousness; constipation; diarrhea; dry, sore eyes; itching; nausea or vomiting; nightmares or intensely vivid dreams; numbness, tingling, or other unusual sensations in the fingers, toes, or scalp.

Possible interactions

Other medicaments:

Metoprolol may increase the effects of:

• other antihypertensive medicaments, causing excessive lowering of blood pressure; dose adjustments may be necessary.
• reserpine (Ser-Ap-Es, etc.) and cause sedation, depression, slowing of the heart rate and lowering of the blood pressure.
• verapamil (Calan, Isoptin) and cause excessive depression of heart function; monitor this combination closely.

Metoprolol taken concurrently with:

• amiodarone (Cordarone) may result in extremely slow heartbeat and cardiac arrest.
• clonidine (Catapres) requires close monitoring for rebound high blood pressure if clonidine is withdrawn while metoprolol is still being taken.
• digoxin (Lanoxin, others) may increase heart slowing.
• fluoxetine (Prozac) may cause metoprolol toxicity.
• fluvoxamine (Luvox) may lead to metoprolol toxicity.
• insulin requires close monitoring to avoid undetected hypoglycemia.
• lidocaine can lead to lidocaine toxicity (cardiac arrest).
• methyldopa (Aldomet, others) can have a rare paradoxical hypertensive response--caution is advised.
• nifedipine (Adalat, Procardia, others) may result in heart failure.
• oral antidiabetic medicaments can result in prolonged hypoglycemia if it occurs.
• phenothiazines can result in low blood pressure or toxicity due to the phenothiazine.
• quinidine (Quinaglute, others) can lead to abnormally slow heartbeat and shortness of breath.
• ritonavir (Norvir) and perhaps other protease inhibitors may cause toxicity.
• tocainide (Tonocard) may lead to depressed contraction ability of the heart (myocardial contractility).
• venlafaxine (Effexor) may lead to metabolic changes and toxic blood levels of both medicines.

The following medicaments may increase the effects of metoprolol:

• alpha one adrenergic blockers, such as prazosin (Minipres).
• cimetidine (Tagamet).
• ciprofloxacin (Cipro).
• diltiazem (Cardizem) and other dihydroperidine calcium blockers, especially in people with decreased function of the left ventricle.
• MAO inhibitors.
• methimazole (Tapazole).
• oral contraceptives (birth control pills); a different (non-first pass) beta blocker is advisable.
• propafenone (Rythmol).
• propoxyphene (Darvocet, others).
• propylthiouracil (Propacil).
• zafirlukast (Accolate) or zileuton (Zyflo); dose decreases of metoprolol may be needed.

The following medicaments may decrease the effects of metoprolol:

• barbiturates (phenobarbital, etc.).
• indomethacin (Indocin) and possibly other aspirin substitutes or NSAIDs may impair metoprolol's antihypertensive effect.
• rifampin (Rifadin, Rimactane).

Foods:

Peak medicament concentration and peak effect will increase if taken with food. Avoid excessive salt intake.

Herbal medicines or minerals:

Valerian and kava kava may intensify drowsiness. Ginseng may increase blood pressure, blunting the benefits of these medicines. Hawthorn, saw palmetto, ma huang, goldenseal, yohimbe and licorice may also increase blood pressure. Calcium and garlic may help lower blood pressure. Indian snakeroot has a German Commission E monograph indication for hypertension-talk to your doctor. Eleuthero root should be avoided by people living with hypertension.

Alcohol:

Alcohol may exaggerate this medicament's ability to lower the blood pressure and may increase its mild sedative effect.

Tobacco smoking:

Nicotine may reduce this medicament's benefit in treating high blood pressure.

Exposure to heat:

Hot environments can lower the blood pressure and exaggerate the effects of this medicament.

Exposure to cold:

Cold environments can increase circulatory deficiency in extremities. The elderly should take care to prevent hypothermia.

Heavy exercise or exertion:

Best to avoid exertion that produces light-headedness, excessive fatigue or muscle cramping. This medicament may intensify the blood pressure response to isometric exercise.

Occurrence of unrelated illness:

Fever can lower the blood pressure and require adjustment of dose. Nausea or vomiting may interrupt the regular dose schedule. Ask your doctor for help.

Discontinuation:

Do not stop this medicament suddenly. Gradual dose lowering over 1 to 2 weeks is recommended. Ask your doctor for help.

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