Succinylcholine's duration of action is prolonged in patients with low plasma pseudocholinesterase activity, potentially leading to extended apnea, and it is contraindicated in heart failure patients on digoxin due to risks of electrolyte imbalances.

Dantrolene acts peripherally by directly affecting muscle contractile mechanisms, making it suitable for chronic spasticity, while centrally acting agents like baclofen target GABA-B receptors in the spinal cord to reduce glutamate release.