* Mephenesin group includes carisoprodol ( it’s metabolite meprobamate is used as a CNS depressant), chlorzoxazone, chlormezanone and methocarbamol. These drugs selectively inhibit polusynaptic reflexes and are useful in local muscle spasms like sprains and spasms due to spondylitis.

* Benzodiazepines like diazepam and clonazepam inhibit both polysynaptic as well as monosynaptic reflexes and are useful in muscle spasms of almost any origin. They are mainly used in spinal injuries and tetanus

* GABA B ( it is a G protien coupled receptor unlike GABA A, which is an ionotropic receptor) agonists like baclofen increase K+ conductance and can inhibit monosynaptic as well as polysynaptic reflexes. Beclofen is used to relieve spasticity in mulitiple sclerosis and spinal injuries. it is not in cerebral palsy.

* Tizanidine is a centrally acting Alpha 2 agonist but unlike clonidine,has no effect on blood pressure. it inhibits the release of excitory neurotransmitters in the spinal cord(by its presynaptic action). it can be used to relieve spasms in multiple sclerosis, amyotrophic lateral sclerosis, other neurological disorders, and spinal injuries.

* Thiocolchicoside is muscle relaxant with anti-inflammatory and analgesic effects. it act as a GABA A and glycine receptor antagonist.it has pro-convulsant action and is avoided in epileptic patients

Q. Shortest acting non depolarizing muscle relaxant is

A. Succinyl choline

B. Rapacuronium

C. Atracurium

D. Pancuronium

Ans: B