Atenolol vs metoprolol: beta blockers compared

At a glance

• Approved for

  Atenolol

  High blood pressure, angina, after a heart attack

  Metoprolol

  Tartrate: high blood pressure, angina, heart attack; succinate: high blood pressure, angina, heart failure

• How it leaves the body

  Atenolol

  Mainly through the kidneys, unchanged

  Metoprolol

  Broken down by the liver (CYP2D6)

• Kidney disease

  Atenolol

  Maximum dose is lowered

  Metoprolol

  No dose change needed

• How often

  Atenolol

  Usually once a day

  Metoprolol

  Tartrate once or twice a day with meals; succinate once a day

• Generic

  Atenolol

  Yes

  Metoprolol

  Yes, both tartrate and succinate

Kidneys or liver

Atenolol undergoes little or no breakdown in the liver and leaves the body mainly through the kidneys, so its label caps the daily dose when kidney function is reduced (50 mg a day for a creatinine clearance of 15 to 35 mL/min, and 25 mg below 15), and people on hemodialysis take it after each session under supervision. Metoprolol is broken down mainly by the liver enzyme CYP2D6: kidney failure does not change its dose, but liver impairment calls for a lower starting dose, and fluoxetine, paroxetine, quinidine and propafenone raise its levels.

The two forms of metoprolol

Metoprolol tartrate (Lopressor) is taken with or right after meals, once or twice a day for blood pressure and twice a day for angina. Metoprolol succinate (Toprol-XL) is an extended-release tablet taken once a day; it is scored and can be split, but whole or half tablets are swallowed without crushing or chewing. Only the succinate form is approved for heart failure, where it lowers the risk of death from heart causes and of hospital stays for heart failure, so the two forms are not interchangeable. Atenolol is not approved for heart failure, and its label says not to use it with overt heart failure.

Never stop suddenly

The atenolol label sets its warning about stopping suddenly in a box, and the Lopressor and Toprol-XL labels give the same warning in their warnings sections: stopping abruptly can worsen chest pain and, in some cases, cause a heart attack in people with coronary artery disease. Doses are reduced gradually and with close observation; the metoprolol labels say over one to two weeks. Because heart disease can go unrecognized, this applies to people taking either medicine for blood pressure alone.

Cautions shared by both

Both labels say beta blockers are generally avoided in asthma and other bronchospastic disease, and are used, if at all, at the lowest effective dose with an inhaler on hand. Both labels warn that beta blockers can hide the fast heartbeat that warns of low blood sugar and can raise the risk of severe or prolonged low blood sugar, especially when fasting, which matters for people with diabetes. Neither is used with a very slow heart rate, heart block beyond first degree or cardiogenic shock, and verapamil, diltiazem and digoxin add to the slowing. Tell surgeons you take a beta blocker; it is not routinely stopped before surgery.

Side effects and pregnancy

Tiredness, dizziness and depression appear on both labels; atenolol’s also lists cold hands and feet, and metoprolol’s lists diarrhea, shortness of breath, slow heart rate and rash. The atenolol label states it can cause fetal harm and has been linked to smaller babies when started in the second trimester. The metoprolol labels say observational studies have not shown a higher risk of major birth defects, but newborns exposed to either may have a slow heart rate or low blood sugar and are watched after birth. Tell your prescriber if you are pregnant, planning a pregnancy or breastfeeding.

Cost

Atenolol, metoprolol tartrate and metoprolol succinate are all available as generics, and each pharmacy sets its own cash price for each form and strength, so ask for a quote on the exact form prescribed, immediate-release or extended-release.

Read more

• Atenolol guide
• Metoprolol guide
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• Metoprolol guide
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