myotoxicity

Myotoxicity refers to toxic injury to skeletal muscle caused by exogenous toxins or metabolic disturbances. It can present as myopathy, myositis, or rhabdomyolysis, ranging from mild weakness to life-threatening muscle necrosis.

Common causes include pharmacologic agents (statins, fibrates, colchicine, daptomycin, linezolid), certain venoms (snake venoms containing myotoxins such as phospholipase A2), alcohol, heavy metals (lead, mercury), illicit drugs, and environmental toxins. Exercise-induced rhabdomyolysis with dehydration or heat can also produce myotoxic injury.

Mechanisms often involve disruption of calcium handling and energy production in muscle fibers, direct membrane damage by toxins, mitochondrial dysfunction and oxidative stress, or immune-mediated injury.

Clinically, patients may have weakness, soreness, and dark urine from myoglobin. Diagnosis relies on history of exposure, elevated serum creatine kinase (often markedly), and, when appropriate, myoglobinuria and renal function tests. Imaging and biopsy may help in unclear cases.

Management focuses on removing the offending agent, supportive care, and preventing complications. This includes aggressive hydration, electrolyte management, monitoring and treating acute kidney injury, and specific antidotes or neutralizing agents when available (for example, antivenoms for certain venoms).

Prognosis and prevention: Prognosis varies with cause and timeliness of treatment. Prevention involves judicious use of myotoxic drugs, dose adjustments, hydration, and avoidance of known toxins in at-risk individuals.