Muscle relaxants: Benzodiazepine

In the perioperative setting, benzodiazepines are frequently used for anxiolysis, amnesia, and sedation. They exert these effects via the gamma-aminobutyric acid (GABA) neurotransmitter system. In particular, they bind to specific sites on the GABA type A receptor complex, enhancing the interaction between the receptor and chloride ion channel. Benzodiazepines may also be used to relieve skeletal muscle spasticity and its accompanying pain in a variety of neurologic disorders including stroke and spinal cord injury. Spasticity likely results from a relative difference between excitatory and inhibitory signals in the spinal cord. Consequently, there is excessive muscle tone and hyperactive stretch reflexes. Benzodiazepines exert their muscle relaxant properties by central potentiation of GABA release. The metabolism of benzodiazepines occurs in the liver, and some have active metabolites (e.g., diazepam). Thus, caution must be exercised to prevent toxicity, including excessive sedation and cognitive impairment.

With regard to intraoperative neuromuscular blockade, typical doses of benzodiazepines (i.e., midazolam) demonstrate minimal, if any, potentiation.