Muscle Relaxants

Front 1

antispastic

Back 1

specific for skeletal m, red spasticity that interferes w/ adl like ms, cp, spinal cord inj

baclofen, dantrolene

bzd, tizanidine also antispastic

Front 2

antispasmodic

Back 2

relieves spasms, m relaxant, adjunct to rest, pt, relief of discomfort w/ msk d/o

cyclobenzaprine

bzd, tizanidine also antispastic

Front 3

spasticity

Back 3

inc tonic stretch reflex (1a sens fiber --> a-motor n, inh intermediate n), flexor m spasms punctuated w/ m weakness, often assoc w/ cp, ms, cva, involves stretch reflex arc + higher centers in cns

dmg desc pathways in spinal cord --> hyperexcitability of a-motor n

tx: red act of 1a afferent fibers and/or a-motor n

Front 4

bzd

Back 4

enh act of gaba at gaba-a R --> open cl channel --> usu hyperpolarization (a-motor n, inh) but can depolarize (1a afferent, disrupt nt release), also anti-anxiety w/in higher cns, partly direct effect on spinal cord since effective on spinal cord transection pt

diazepam most common, use red spasticity from multiple etiologies, ae sedation

Front 5

baclofen

Back 5

lisoresal, gaba-b R agonist (metabotropic) on 1a afferent + motor n --> open k channel (out), close ca channel (in) --> hyperpolarization, also red pain by inh substance p

active po (rapid withdrawal --> hallucination/seizure), adjust for kidney fxn, intrathecal for severe spasticity (doesn't leak out so higher dose possible, inc qol but problem maintaining cath)

use ms (esp flexor spasm, concomitant pain), clonus, m rigidity, spinal cord inj, not helpful for cva pt or rheumatic --> skeletal m spasm

Front 6

tizanidine

Back 6

a2 agonist, congener of clonidine (less hypotensive, more cns), act prexynaptic R on 1a afferent term --> dec glu release

po, onset 1.5 hr, hl 2.5 hr, up to 6 hr, 95% first pass

use ms/spinal inj, central/periph effect, comparable efficacy to diazepam, baclofen, dantrolene but diff ae (sedation, hypotension, dry mouth, lose strength, dizziness)

adjust for renal impair, inc lft, additive cns-dep action w/ diazepam/etoh, may inc conc phenytoin

Front 7

dantrolene

Back 7

dantrium, periph acting, inh ca release from ryanodine channel on sr of skeletal m (not cardiac/smooth), tx (neuroleptic) malignant hyperthermia (inherited, pts can't sequester ca in sr, neuromuscular blockingagent or ga --> massive release ca --> massive contraction --> lactic acid prod, inc temp)

po 1/3 abs, hl 8 hr, ae general weakness, sedation, chem hepatitis

Front 8

cyclobenzaprine

Back 8

use acute m spasm, inh serotonergic input to m nn (local tissue trauma, m strain), related to tricyclic antidepressant so antimuscarininc (dry mouth, avoid in elderly or glaucoma pts), long qt (avoid in arrhythmia pts)

Front 9

gabapentin

Back 9

ns indirectly acting gaba agonist, anti epileptic

Front 10

riluzole

Back 10

rilutek, inh glu release (also red neuronal deg), inact v-dep na channel, use als

Front 11

botulinum toxin

Back 11

inh ach release, local im for generalized spastic d/o like cp

Front 12

botulinum toxin

Back 12

inh ach release, local im for generalized spastic d/o like cp