Skeletal Muscle Relaxants PDF

Part 4 4: Sk keletal Muscle M Relaxan nts Classiffication Dru ugs act on n brain hig ers: e.g. ca gher cente arisoprodo...

Part 4 4: Sk keletal Muscle M Relaxan nts Classiffication Dru ugs act on n brain hig ers: e.g. ca gher cente arisoprodo ol, benzodi azepines, general ane esthetics, anticonvuls a sant drugs , and antip parkinsonia an drugs (ssee later). Dru ugs act on n neurona al cord: e..g. tizanidine and al transm ission in the spina bac clofen. Dru ugs act onn the neu on: e.g. ne uromuscullar junctio euromuscuular blocke ers and boto olinum tox xin. Dru ugs act dirrectly on the t muscle anisms: e..g. dantrole e contracttile mecha ene. 1. Carrisoprodo ol  Carrisoprodol – (and its metabolitee mebrobamate) – are centraally acting skeletal musscle relaxxants. Their mechan nism is unclear but seems to be sim milar to barrbiturates.. They bind d to GABAAA recepto ors in the CNS C leadi ng to antia anxiety, antiiconvulsan nt, and ske eletal musc cle relaxatio on.  Thee drug and its metabo olite have a abuse potential, so so ome countrries limit its s use. 343  2. Baclofen  Baclofen is a GABA derivative that selectively stimulates GABAB receptors in the spinal cord → ↓ release of excitatory transmitters.  It is used as a skeletal muscle relaxant in neurological spastic conditions. 3. Tizanidine  Tizanidine is a centrally acting α2 agonist with greater effect on presynaptic α2 in the spinal cord, so it inhibits neurotransmission and reduces muscle spasm with minimal effect on blood pressure. 4. Dantrolene  Dantrolene inhibits Ca2+ release from the sarcoplasmic reticulum of skeletal ms cells. It acts directly on the muscle contractile mechanisms.  It is used for emergency management of malignant hyperthermia (1 mg/kg i.v.) 5. Botulinum toxin (Botox)  Botulinum toxin is a neurotoxic protein produced by the bacterium Clostridium botulinum. It inhibits the release of ACh from motor nerve terminals leading to skeletal muscle paralysis.  It is injected locally to treat local muscle spasm e.g. in cervical dystonia (spasmodic torticollis), and blepharospasm (uncontrolled muscle contraction or twitch of the eyelid). It is also used for cosmetic reduction of facial wrinkles. 6. Neuromuscular blockers: see ANS. Mephensin Therapeutic uses of skeletal muscle – Mephensin is a selective relaxants inhibitor of polysynaptic excitation of the spinal motor  Neurological spastic conditions such as neurons through stimulation of multiple sclerosis, back pain, and spine glycine receptors in the spinal injuries. cord.  Dantrolene is used for emergency man- – It was historically used as agement of malignant hyperthermia. antidote for treatment of  Botolinum toxin is injected locally to relive strychnine poisoning but its blepharospasm, and for cosmetic clinical use now is very limited because of serious side reduction of facial wrinkles. effects including respiratory  Neuromuscular blockers are used to depression and hemolysis. produce muscle relaxation during surgical procedures. 344