skeletal muscle relaxants -decr ms tone

1. peripherally acting on NMJ Nm receptors (i.v. for short procedures) (quaternary -no BBB/oral/placenta) – nondeplz[dTB], deplz[SCh] –> paralysis(voluntary movts lost)
2. directly acting on ms by decr Ca+2 release – dantrolene –> drug of choice in malignant hypothermia(from flourinated anaesthetics/SCh in succeptibles), decr UMNDspacticity in hemi/paraplegia,Cpalsy,MS,ALS,spinal inj.incr RP & decr excitation quinine -use in myotonia congenita, nocturnal leg cramps [ADR-decr ms strength,sedation,diarrhoea,liver toxicity]
3. spamolytics acting centrally by decr spinal supraspinal reflexes of ms tone without affecting stretch reflex [ADR-sedation]–>
   • pain<–>spasm: acute (overstretch,sprain,tear, dislocation,bursitis, rheumatoid disorders), torticollis,lumabago,backacke,neuralgias -mephenesin like/DZP +analgesics.
   • deseased desc pathways(UPMND)–>spasticity: decerebrate rigidity, hemi/paraplegia, MS,ALS, Cpalsy, parkinsonism, spinal inj, stroke -DZP,baclofen,tizanidine.
   • hyperreflexia of anxiety -DZP,chlormezanone.
   • ECT, ortho manipulations,tetanus -DZP [w/ SCh]

nondeplz/competitive Nm blocker	deplz/noncompetitive Nm blockers
bulky molecule – metabolized by AChE.	slender long flexible -cant be disossiated.
affinity to alfa subunits  + physically block preventing subunits conformational changes.	affinity to alfa subunits + intrinsic partial deplz of Na+ ch.
no Na+ ch opening -decr end plate pot -no AP –> initial weakness, flaccid paralysis first of small/fast response ms[eye,limbs] & last on head trunk[diaphragm] –> use in ocular,abd,thoracic surgery to produce adequate ms relxn & decr reflex contr during light anaesthesia [among more potent long acting drugs -pancuranium is inexpensive so used in developing countries] severe tetanus & status epilepticus uncontrolled by DZP. rocuranium intermediate acting use in intubation w/out SCh ADRs. [ADR- prolonged apnoea w/ long acting drugs: dTB,pan,dox,pipe -neostigmine reversal required]	Na+ ch in open inactivated state –> initial fasciculatiins [soreness in man]. decr EPP -no AP –> flaccid paralysis [phase1]  rapid onset & recovery w/out the ms sequence appreciation & only transient apnoea –> use intubation, endoscopy, ortho manipulations, ECT. [ADR- prolonged/high dose SCh/deficient pseudoChE/florinated anaesth --> phase2 slow onset & recovery of desensitization to ACh --> prolonged apnoea]
dTB,pancuronium,vecocuranium -block autonomic ganglia[Nn] –>vagal tachycardia. decr BP by ganglion block+limb ms paralysis+histamine (CI- hypovolemia, hepatic/renal insufficiency – so CISATRACURIUM can be used /w does not release histamine & undergoes hoffman elimination spontaneously in plasma)	SCh stimulates autonomic ganglia –> vagal brdycardia initially, later sympth tachycardia. sympth HTN, incr postoperative Paralyticileus.
dTB causes high histamine release -flushing, decr BP, brspasm & incr secretions(ppt asthma) [not w/ cisatracurium, rocurarium]	low histamine release -flushing
	burns/tetanus + prolonged SCh deplz –> hyperkalaemia -arrhyth [CI- digitalized Pt]