Simple FactSheet: Myopathy, Cardiomyopathy, Myositis

Myopathy, Cardiomyopathy, Myositis
a Simple FactSheet from the AIDS Treatment Data Network

||||| Myopathy and cardiomyopathy:

This side effect is thought to be caused by damage to the mitochondria in muscle cells.

||||| Symptoms:

Symptoms are weakness and loss of muscle tissue in the arms, legs and buttocks. This type of toxicity can also affect the heart muscle, a problem called cardiomyopathy.

||||| Drugs responsible:

This side effect is most often associated with zidovudine (AZT, Retrovir), but has also been reported with stavudine (d4T, Zerit).

||||| Risk of experiencing this side effect:

Myopathy has been reported in 6% (around 1 in 20) of people taking Retrovir for more than 6 months, although the problem may have been more frequent when higher doses were used. A study has also found that the length of time taking the drug is the biggest risk factor for developing myopathy. There is no information on the risk of developing Retrovir-related myopathy in people taking the drug for more than two years. A very recent report has shown that Zerit can cause myopathy, but the number of people likely to experience this problem is not yet known for certain.

The risk of developing cardiomyopathy is uncertain. A recent experimental study in mice found that HIV proteins were linked to cardiomyopathy, but that Retrovir made the problem significantly worse. What happens in people is more difficult to figure out. A 1995 study found that children taking Retrovir were over 8 times more likely to develop this problem than children taking ddI or no treatment. An Italian study from 1998 found that people taking Retrovir were at greater risk for developing cardiomyopathy, but that the problem was also linked to HIV infection regardless of treatment. In this study, 76 out of a group of 952 people (8%, or about 1 in 12) were diagnosed with cardiomyopathy. A study from Cook County hospital in Chicago found evidence of cardiomyopathy in 20 out of 84 people (1 in 4), but the differences between this and the Italian study may be due to the history of drug use in the people involved. A history of cocaine abuse has been linked to cardiomyopathy, and this can make it even harder to sort out how much Retrovir and/or HIV contribute to the problem. As yet, there is no information on Zerit and cardiomyopathy.

||||| Diagnosis:

A blood test for an enzyme called creatinine kinase (CK or CPK) is used to help diagnose myopathy. CK levels are often higher than normal in people with myopathy. Normal CK levels are generally 10-79 u./L for women and 17-148 u./L for men. Taking a small piece of muscle tissue (a muscle biopsy) and studying it under the microscope can show if the mitochondria in muscle cells are damaged. In the case of cardiomyopathy, a heart test called an echocardiogram can help look for problems with heart function. Studies are needed to work out if regular echocardiograms should be done in people taking anti-HIV drugs, particularly Retrovir or Zerit.

||||| Treatment:

Because there is no known treatment for NRTI-related myopathy, the best approach may be to identify the drug that is causing it. If possible, an alternative anti-HIV drug can then be substituted. A study published in 1998 looked at muscle biopsies from people with Retrovir-related myopathy. The researchers found that mitochondrial damage in the muscle tissue improved rapidly after Retrovir was stopped.

||||| Myositis:

A related problem is called myositis, which is when toxicity to mitochondria in the muscle tissue causes inflammation, pain and muscle damage. Like with myopathy, zidovudine is the most commonly reported cause of myositis. Myositis can be acute, which means it happens soon after starting the drug. The major symptom is muscle pain. Switching to another drug is necessary if myositis develops.

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\|\|\|\|\| Myopathy and cardiomyopathy:
This side effect is thought to be caused by damage to the mitochondria in muscle cells.
\|\|\|\|\| Symptoms:
Symptoms are weakness and loss of muscle tissue in the arms, legs and buttocks. This type of toxicity can also affect the heart muscle, a problem called cardiomyopathy.
\|\|\|\|\| Drugs responsible:
This side effect is most often associated with zidovudine (AZT, Retrovir), but has also been reported with stavudine (d4T, Zerit).
\|\|\|\|\| Risk of experiencing this side effect:
Myopathy has been reported in 6% (around 1 in 20) of people taking Retrovir for more than 6 months, although the problem may have been more frequent when higher doses were used. A study has also found that the length of time taking the drug is the biggest risk factor for developing myopathy. There is no information on the risk of developing Retrovir-related myopathy in people taking the drug for more than two years. A very recent report has shown that Zerit can cause myopathy, but the number of people likely to experience this problem is not yet known for certain. The risk of developing cardiomyopathy is uncertain. A recent experimental study in mice found that HIV proteins were linked to cardiomyopathy, but that Retrovir made the problem significantly worse. What happens in people is more difficult to figure out. A 1995 study found that children taking Retrovir were over 8 times more likely to develop this problem than children taking ddI or no treatment. An Italian study from 1998 found that people taking Retrovir were at greater risk for developing cardiomyopathy, but that the problem was also linked to HIV infection regardless of treatment. In this study, 76 out of a group of 952 people (8%, or about 1 in 12) were diagnosed with cardiomyopathy. A study from Cook County hospital in Chicago found evidence of cardiomyopathy in 20 out of 84 people (1 in 4), but the differences between this and the Italian study may be due to the history of drug use in the people involved. A history of cocaine abuse has been linked to cardiomyopathy, and this can make it even harder to sort out how much Retrovir and/or HIV contribute to the problem. As yet, there is no information on Zerit and cardiomyopathy.
\|\|\|\|\| Diagnosis:
A blood test for an enzyme called creatinine kinase (CK or CPK) is used to help diagnose myopathy. CK levels are often higher than normal in people with myopathy. Normal CK levels are generally 10-79 u./L for women and 17-148 u./L for men. Taking a small piece of muscle tissue (a muscle biopsy) and studying it under the microscope can show if the mitochondria in muscle cells are damaged. In the case of cardiomyopathy, a heart test called an echocardiogram can help look for problems with heart function. Studies are needed to work out if regular echocardiograms should be done in people taking anti-HIV drugs, particularly Retrovir or Zerit.
\|\|\|\|\| Treatment:
Because there is no known treatment for NRTI-related myopathy, the best approach may be to identify the drug that is causing it. If possible, an alternative anti-HIV drug can then be substituted. A study published in 1998 looked at muscle biopsies from people with Retrovir-related myopathy. The researchers found that mitochondrial damage in the muscle tissue improved rapidly after Retrovir was stopped.
\|\|\|\|\| Myositis:
A related problem is called myositis, which is when toxicity to mitochondria in the muscle tissue causes inflammation, pain and muscle damage. Like with myopathy, zidovudine is the most commonly reported cause of myositis. Myositis can be acute, which means it happens soon after starting the drug. The major symptom is muscle pain. Switching to another drug is necessary if myositis develops.