• Myopathy: enthusiasm for liberal use of neuromuscular blockings agents has waned because of myopathy
• Myasthenia gravis: usually resistant to SCh and highly sensitive to nondepolarizing muscle relaxants
• Myotonia: sustained contracture in response to SCh; normal response to nondepolarizing muscle relaxants
• Muscular dystrophy: SCh is contraindicated
• Neurologic diseases: isolated reports of hyperkalemia in response to SCh
• Hemiplegia or paraplegia: hyperkalemia in response to SCh; resistant to nondepolarizing muscle relaxants
• Burn injury: hyperkalemia in response to SCh; resistant to the effects of nondepolarizing muscle relaxants

SCh = succinylcholine.