Drug-Induced Myopathy: These 7 Medications May Cause Muscle Weakness

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It's uncomfortable to experience myopathies - better known as muscle injury. Muscle pain, cramps, and weakness can all have an underestimated impact on well-being. Of these, weakness is one of the most common issues that people experience.

Something as simple as strenuous exercise could be responsible for these symptoms. But myasthenia gravis, multiple sclerosis, and other conditions could also be a cause. Medications are sometimes the root issue too.

Like a detective, you're probably looking for clues to find the source. Together with your healthcare professional, you can determine if a medication is contributing to your discomfort.

We'll discuss seven medications that can cause drug-induced myopathy, specifically muscle weakness.

1. Statins and other cholesterol medications

Statins are among the most prescribed medications to manage cholesterol. Atorvastatin (Lipitor, Atorvaliq), simvastatin (Zocor, FloLipid), and rosuvastatin (Crestor) are all go-to choices.

Muscle-related symptoms - such as muscle pain and weakness - are common statin side effects. Researchers believe genetics, calcium leakage, and other factors may contribute to drug-induced myopathy. Statins can also lower levels of the antioxidant coenzyme Q10 in the body. This could play a role in muscle pain.

Taking a statin with other cholesterol medications that cause muscle weakness can be dangerous. In fact, simvastatin's label says it shouldn't be taken with the fibrate gemfibrozil (Lopid) at all. That's because the duo raises the chances of experiencing rhabdomyolysis (muscle breakdown).

Rhabdomyolysis can cause kidney damage and may be life-threatening in some cases. Warning signs to watch for include muscle weakness, pain, and dark-colored urine. If you experience these symptoms, seek medical care immediately.

Good to know: Your healthcare professional will likely check your creatine phosphokinase levels with a blood test if you experience muscle weakness while taking a statin. This test checks for muscle damage.

2. Corticosteroids

Corticosteroids treat many inflammatory health conditions, such as eczema and asthma. Prednisone (Rayos), methylprednisolone (Medrol), and dexamethasone are a few examples. They're effective at lowering inflammation, but there may be side effects, especially with long-term use. One is drug-induced myopathy.

Corticosteroids cause muscle weakness in a variety of ways. For instance, they can change how muscle fibers behave. Corticosteroids can also lower potassium levels in your body. Potassium is a mineral that helps your muscles do their job. If you have low potassium, you can experience muscle weakness.

Long-term corticosteroid use (4 weeks or more) typically carries a higher risk of medication-related myopathy. But high-dose corticosteroids given over a short period of time can also cause it.

Oral and injectable corticosteroids are most likely to cause muscle weakness. This isn't a known risk with topical corticosteroids.

3. Amiodarone

Amiodarone (Pacerone) is an antiarrhythmic medication that manages heart rhythm conditions. Amiodarone is rarely linked to drug-induced myopathy because of how it affects muscle fibers.

This is more likely if you have kidney problems or are taking other medications - such as statins - that can also cause muscle weakness. If you're taking a higher amiodarone dose, you may experience movement problems too.

4. Cancer treatments

Cancer treatments can be life-saving and life-extending. But they also carry a risk of side effects. Chemotherapy and immune checkpoint inhibitors are two types of cancer treatments linked to drug-induced myopathy.

Doxorubicin, cisplatin, and fluorouracil are chemotherapy treatments that may cause muscle weakness. The immune checkpoint inhibitors nivolumab (Opdivo) and pembrolizumab (Keytruda) can rarely cause muscle inflammation and weakness. This often happens within a few weeks of starting them.

5. HIV medications

Thanks to modern advances, HIV medications have fewer side effects today than in the past. But a couple of HIV medications can still cause drug-induced myopathy.

Zidovudine (Retrovir), commonly referred to as AZT, can cause muscle weakness. AZT is also included in other combination medications, such as lamivudine / zidovudine. Researchers believe this older HIV tablet affects mitochondria (the cell's energy house). If your muscle cells don't have enough energy, you may experience muscle weakness. Zidovudine isn't a first-choice medication because it has a lot of side effects.

Raltegravir (Isentress, Isentress HD) is an integrase inhibitor. It can cause muscle weakness and in rare cases, rhabdomyolysis. If you experience any symptoms of rhabdomyolysis, tell your healthcare professional right away.

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Good to know: People living with HIV often experience muscle weakness. If you have questions or concerns about muscle weakness, ask your healthcare professional.

6. Fluoroquinolone antibiotics

Fluoroquinolones, such as levofloxacin and ciprofloxacin (Cipro), are antibiotics that treat bacterial infections. But it's best to avoid them for mild infections. They carry a risk of antibiotic resistance and serious side effects. These include drug-induced myopathy. It's better to use them for severe infections only.

Fluoroquinolones even carry a boxed warning - the FDA's most serious medication warning - about worsening muscle weakness in people with myasthenia gravis. If you have myasthenia gravis, it's best to avoid fluoroquinolones.

7. Colchicine

Colchicine (Colcrys, Mitigare, Gloperba) is FDA approved to prevent and treat gout flares. It's also approved to manage the autoimmune condition familial Mediterranean fever. But in rare cases, colchicine may cause drug-induced myopathy.

In general, there's a higher chance of muscle weakness in people with kidney problems. But certain medications and foods also interact with colchicine, causing it to build up in the body. This makes it more likely to experience muscle weakness.

Examples of these medications include:

• Certain statins, such as atorvastatin and simvastatin

• Grapefruit or grapefruit juice

• Azole antifungals, such as fluconazole (Diflucan) and ketoconazole

• Macrolide antibiotics, such as azithromycin (Zithromax) and clarithromycin

• Calcium channel blockers, such as diltiazem (Cardizem) and verapamil

• Protease inhibitors, such atazanavir (Reyataz) and darunavir (Prezista)

• Cyclosporine (Sandimmune, Gengraf, Neoral)

Other medications that have been connected to muscle weakness

In addition to the medications mentioned above, many others may cause muscle weakness as a side effect. Additional examples include:

• Cyclosporine

• Propofol (Diprivan)

• Chloroquine

• Hydroxychloroquine (Plaquenil)

• Omeprazole (Prilosec)

• Finasteride (Proscar)

• Isotretinoin (Claravis, Absorica)

• Phenytoin (Dilantin, Phenytek)

• Lamotrigine (Lamictal)

• Labetalol

• Metformin (Fortamet, Glumetza)

Can drug-induced myopathy be reversed?

Yes, myopathy can usually be reversed. Muscle weakness often gets better after your body gets used to your medication.

If this doesn't happen, your healthcare professional may lower your medication dose. This works well when side effects of your prescription are thought to be dose related.

Switching to a different medication may also do the trick, especially if you need to take it long term. For instance, if you experience muscle weakness while taking simvastatin, your healthcare professional may switch you to another statin, such as rosuvastatin.

Stopping your medication is another option. After you've stopped the offending medication, your muscle weakness should get better.

Good to know: Keep an updated list of the medications and supplements that you take. Your prescriber and pharmacist can check for interactions that raise the risk of drug-induced myopathy.

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