Definition: Generalised destructive effects on the skeletal musculature.

Signs and symptoms:

• Muscle pain, spasms, weakness and paralysis,
• myoglobinuria,
• hyperkalaemia.

Myotoxicity as defined here does not include localised muscle necrosis, which is of particular significance following snakebites. Localised muscle necrosis at the site of venom application is discussed in "Local venom/poison effects". It is not usually accompanied by generalised rhabdomyolysis and is commonly of secondary origin.

Marked systemic myotoxic envenoming, such as is typical for some Australian elapids, Hydrophiidae and the South American rattlesnake (Crotalus durissus terrificus), is generally not accompanied by significant local manifestations. It is associated with specific phospholipases A that act systemically on muscle membranes (see "Neurological venom/poison effects"). This probably causes hydrolysis of plasma membranes, thus leading to rhabdomyolysis. Hyperkalaemia and secondary renal failure may result.

A surprising aspect of systemic myotoxic envenoming is that the basal lamina of the muscle fibres remains intact. This means that regeneration of the affected musculature is possible. Regeneration usually takes place within 21–28 days (Harris 1989).
          
Literature: Harris 1989, Mebs and Ownby 1990, Mebs et al. 1983