Extreme Side Effects Of Metoprolol

Metoprolol belongs to the class of medications known as beta blockers. It is most commonly prescribed to treat high blood pressure and chest pain, also called angina, and sometimes given to prevent migraine headaches. Metoprolol slows the heart rate and dilates blood vessels, reducing blood pressure and improving blood flow. Many people take metoprolol in either its short- or long-acting forms, and it is considered generally safe if taken as prescribed. However, like every medication, metoprolol has side effects, some of them dangerous.

Low Heart Rate

Metoprolol's potentially most serious side effect is an extreme version of its intended effect: lowering the heart rate. Normal heart rate is between 60 and 100 beats per minute. If the heart rate drops lower, lack of oxygen may cause faintness, dizziness and even passing out. According to the Mayo Clinic, patients on metoprolol who faint or who sustain a low heartbeat for more than a few minutes should notify their physicians. Taking too much metoprolol is very dangerous. Signs of overdose include blue fingernails and lips, confusion, extreme sleepiness and loss of consciousness. In extreme overdose the heart can stop beating.

Dizziness Upon Rising

Metoprolol's affect on blood pressure may cause orthostatic hypotension, a condition in which the body has difficulty adjusting blood pressure abruptly to meet the body's needs. For some people on metoprolol, getting up suddenly from a lying or seated position causes dizziness, lightheadedness or fainting. Falls and injuries can result. Getting up slowly can prevent this side effect.

Heart Failure

Metoprolol has been known to cause heart failure or make existing heart failure worse. Symptoms of worsening heart failure include shortness of breath, chest pain, swelling of the feet and legs, sudden weight gain, wheezing or visibly dilated neck veins.

Masking Hypoglycemia

Diabetic patients, especially those on insulin, are at risk for low blood sugar, also called severe hypoglycemia. A rapid heartbeat, one sign of hypoglycemia, generally alerts diabetic patients to the onset of a hypoglycemic episode, and they can then eat or drink something to prevent it. However, metoprolol may prevent acceleration of the heart rate during a hypoglycemic episode, masking this important warning sign.

Effects on Allergies

According to MedlinePlus, metoprolol may make allergies worse, and it may interfere with emergency medicine for serious allergies. People who carry injectable epinephrine for allergic emergencies may find that the usual dose of epinephrine does not stop an allergic reaction. Thus people with life-threatening allergies may be at extreme risk if exposed to the allergen while on metoprolol.

Rebound Effects

Stopping metoprolol abruptly may cause the heart rate to increase to dangerous levels through a mechanism called rebound cardiac excitation. The increased heart rate may cause chest pain or a heart attack. The Mayo Clinic advises patients to consult their doctors before discontinuing this medication.