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Muscle weakness

Raltegravir (Isentress) is a highly effective and generally safe part of potent combination therapy for HIV infection. There have been rare reports of cases of raltegravir-associated rhabdomyolysis—the breakdown of muscle tissue leading to muscle weakness.

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Muscles are highly active tissues, which require a lot of oxygen. They contain a protein called myoglobin that captures oxygen from the blood and helps to bring this gas to parts of the muscle that burn fuel to release energy. When muscles are damaged they release myoglobin into the blood. This protein and the products into which it is broken down can—in large amounts—cause kidney dysfunction.

Rhabdomyolysis can occur under the following circumstances:

  • alcoholism
  • serious accidents where tissues are compressed (crush injuries)
  • exposure to stimulants such as amphetamine and methamphetamine, cocaine, ecstasy and excessive caffeine
  • inherited muscle disorders
  • heat stroke
  • muscle injury arising from veins being blocked by blood clots
  • lower-than-normal levels of phosphorus in the body
  • seizures
  • very intensive and exhaustive exercise
  • chills
  • many medicines have been associated with rhabdomyolsis but one class stands out: statins (a group of drugs used to treat high cholesterol levels)

Rhabdomyolysis may not initially cause symptoms but the following signs may appear later:

  • dark-coloured urine
  • decreased production of urine
  • fatigue
  • stiff or aching muscles
  • tender muscles
  • painful joints
  • seizures

Lab tests

Blood tests may reveal abnormal levels of an enzyme called creatine kinase. Levels of the waste product creatinine may also be abnormal.

Treatment

In some cases, nurses may provide intravenous saline solution to hydrate the body. This solution, in cases of rhabdomyolysis, may also be rich in bicarbonate to help increase the production of urine and accelerate the removal of myoglobin.

In very severe cases of rhabdomyolysis, dialysis (artificial filtration of the blood) may be necessary to remove myoglobin and other proteins temporarily.

Some people quickly regain their energy after being treated for rhabdomyolysis, while others can have fatigue and muscle aches for several months after treatment.

—Sean R. Hosein

REFERENCE:

Parekh R, Care DA, Tainter CR. Rhabdomyolysis: advances in diagnosis and treatment. Emergency Medicine Practice. 2012 Mar;14(3):1-15.