Harvard Health Letter

5 common medications that can have serious side effects

Report new symptoms immediately if you take one of these.

Taking blood thinners and prescription painkillers such as opioids can have potentially life-threatening complications. But many medications — even over-the-counter drugs — have the potential for dangerous side effects. “In most cases, the risk of serious side effects is very rare — much less than 1% of the time,” says Dr. Joshua Gagne, a pharmacist and epidemiologist with Harvard-affiliated Brigham and Women’s Hospital.

If you’re taking any of the following drugs, learn the rare risks.

1. ACE inhibitors

Angiotensin-converting enzyme (ACE) inhibitors — such as captopril (Capoten), lisinopril (Prinivil), and ramipril (Altace) — are prescribed to lower high blood pressure. The drugs help the body produce less angiotensin, a chemical that narrows blood vessels.

The rare risks: ACE inhibitors may trigger an allergic-type reaction called angioedema, a rapid swelling under the skin that can lead to swelling of the throat and tongue and difficulty breathing. “It could show up on the eyelids or around the mouth, or it may occur with hives on the chest,” Dr. Gagne says.

2. Diabetes medications

Metformin (Glucophage, Riomet) is one of the most common treatments for type 2 diabetes. It decreases the liver’s production of glucose (sugar that provides energy to cells), makes cells more sensitive to the hormone insulin (which moves glucose into cells), and decreases the absorption of glucose from the intestine. “It can cause upset stomach and diarrhea, but that usually goes away with continued use,” Dr. Gagne notes.

The rare risks: Metformin may cause lactic acidosis, an accumulation of lactic acid in the blood that can lead to hypothermia (low body temperature) and a drop in blood pressure. Symptoms include muscle pain, severe abdominal pain, unusual fatigue, and fast breathing.

3. Statins

Statins, such as atorvastatin (Lipitor), simvastatin (Zocor), rosuvastatin (Crestor), and lovastatin (Mevacor), help lower “bad” LDL cholesterol and have been shown to reduce the risk of heart attack, stroke, or death. “About 10% of people who take statins can get muscle aches. It’s not serious, but it causes people to stop taking statins,” Dr. Gagne says.

The rare risks: Statins may cause a potentially life-threatening breakdown in muscle cells, which can overwhelm the kidneys with muscle proteins, causing the kidneys to fail.

4. Over-the-counter painkillers

Acetaminophen (Tylenol) and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin) or naproxen (Aleve) are often the go-to drugs for fevers or headaches, and NSAIDs are also used for body aches.

The rare risks: Large daily doses of acetaminophen — more than 3,000 milligrams — can damage the liver and lead to liver failure. Drinking alcohol while taking acetaminophen can also cause liver damage. Long-term and even short-term NSAID use is linked to ulcers, stomach bleeding, kidney problems, high blood pressure, and increased risk for heart attack or stroke.

5. Fluoroquinolone antibiotics

A class of antibiotics called fluoroquinolones, such as ciprofloxacin (Cipro) and levofloxacin (Levaquin), were once popular medications to treat sinus and urinary tract infections. They are prescribed less often today because of side effect concerns.

The rare risks: Since 2008, the FDA has been warning about the drugs’ potential risks for irreversible side effects. First it was tendon ruptures, then peripheral neuropathy (numbness and tingling from irritated nerves), and more recently (2018) damage to the aorta, the body’s main artery. “I’m not convinced about the risk for aortic damage,” Dr. Gagne says. “I’m studying it now with a group at our hospital.”

How to stay safe

If your doctor prescribes any of the medications we’ve described, ask why it’s necessary and whether the risks are warranted. In some cases, such as taking statins, the benefits typically outweigh the risks. Muscle pain is annoying, and there is rare risk of muscle cell breakdown causing weakness and kidney injury. “But coming off a statin and then having a major heart problem is also a bad outcome. If you experience muscle pain, talk to your doctor about changing to a different statin or a lowering the dose,” Dr. Gagne says.

Be sure to take your medications as prescribed. Also, follow dosage rules for over-the-counter painkillers, unless your doctor advises otherwise.

And stay vigilant about watching for new symptoms. Any sudden side effects you experience — such as abdominal pain, breathing difficulty, hives, swelling, or muscle cramps — should be reported to your doctor immediately, and may require a trip to the emergency department.

Image: skhoward/Getty Images

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