Rhabdomyolysis is the breakdown of skeletal muscle due to injury. The injury can be from physical damage to the muscle, but significant cases of rhabdomyolysis are more commonly due to high fever or hyperthermia, metabolic disorders , excessive exertion, convulsions, choreoathetosis, muscle trauma, flow of electric current through the body or anoxia of the muscle (e.g. Bywaters' syndrome , a tourniquet left for several hours, local muscle compression due to comatose states, etc.).
A large number of drugs may cause rhabdomyolysis through several mechanisms, such as myotoxicity (for example, animal toxins , antibiotics, statins, alcohol, etc), circulatory ischemia, hyperpyrexia, long duration muscle rigidity and others. Drug-induced rhabdomyolysis is more common nowadays than in the past, due to the introduction of increasingly more potent drugs into clinical practice. Any drug which directly or indirectly impairs the production or use of adenosine triphosphate (ATP) by skeletal muscle, or increases energy requirements so as to exceed ATP production, can cause rhabdomyolysis (Larbi, 1998).
Severe cases of rhabdomyolysis often result in myoglobinuria , a condition where the myoglobin from muscle breakdown spills into the urine, making it dark, or "tea colored" (myoglobin contains iron, like hemoglobin, giving muscles its characteristic red color). This condition can cause serious kidney damage in severe cases. The injured muscle also leaks potassium, leading to hyperkalemia, which may cause fatal disruptions in heart rhythm. In addition, myoglobin is metabolically degraded into potentially toxic substances for the kidneys. Massive skeletal muscle necrosis may further aggravate the situation, by reducing plasma volumes and leading to shock and reduced bloodflow to the kidneys.
Calcium levels are initially low (hypocalcemia), as circulating calcium precipitates in the damage muscle tissue, presumably with phosphate. When the acute renal failure resolves, vitamin D levels rise rapidly, causing hypercalcemia (elevated calcium). Although this resolves eventually, high calcium levels may require treatment with bisphosphonates (e.g. pamidronate ).
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