Skeletal muscle relaxants.department of pharmacology

Skeletal muscle relaxants.department of pharmacology

1. SKELETAL MUSCLE RELAXANTS

2. Neuromuscular Junction 1: Cholinergic motor neurone,2: motor end-plate, 3: vesicles, 4: N M R, 5: mitochondrion

3. PERIPHERALLY ACTING NEUROMUSCULAR BLOCKING AGENTS   NON DEPOLARISING AGENTS [COMPETETIVE BLOCKERS] Long acting - d– Tubocurarine , Pancuronium , doxacurium . Intermediate acting- vecuronium,Atracurium Short acting- mivacurium

4. DEPOLARISING Succinylcholine Decamethonium . Directly acting Dantroline sodium

5. Competetive blocking -Non depolarizing combine with the receptors in the end plate denying the access of Ach to the receptors and thus blocks end plate depolarization Flaccid paralysis DEPOLARISING AGENTS: Fasciculations , flaccid paralysis Produce persistant depolarization and an electrical inexcitability of the structure with failure of further excitation by Ach molecules.

6. CURARE ALKALOIDS HISTORY- The curare plant extract was used by natives of South. America to kill wild animals. Arrows dipped in the extract was shot… Animals are caught alive. D- tubocurarine Absorption: Not absorbed from the GIT.  1V action lasts for 30-40mts Fate 25% exereted in urine does not cross placental barrier

7. Actions Flaccid paralysis Ganglionic blockade Histamine release Vagal blockade

8. Succinylcholine Fasciculations Onset- 1-1.5 min. Duration-5-8 min In Deficiency of pseudocholinesterase as genetic disorder Succinylcholine apnoea occurs ADR Hyperkalemia Cardiac arrhythmias

9. Pancuranium Little ganglionic blockade Low histamine release Better CVS stability Long acting, needing reversal Vecuronium Short duration of action

10. ATRACURIUM: Rapid on set of action. At body temperature it breaks down spontaneously and (Hoffman’s elimination) ROCURONIUM RAPID ONSET, intermediate duration of action

11. Drug interactions Choline esterase inhibitors such as neostigmine , pyridostimine and edrophonium reduces or overcome their activity. DRUGS WHICH POTENTIATE TUBOCURARINE ANAESTHETICS: Ether, Halogenated hydrocarbons , calcium channel blockers. Antibiotics: Aminoglycosides antibiotics. 7/10/2020 12

12. ADVERSE EFFECTS: Respiratory paralysis, apnoea Flushing Fall in BP, CV collapse Cardiac arrhythmias, cardiac arrest Precipitation of asthma Post operative muscle soreness, myalgia Malignant hyperthermia 13

13. Uses 1 )Adjuvant in surgical anaesthesia . 2 ) orthopaedic procedures such as corredtion of fractures. 3) Laryngoscopy,bronchoscopy and oesophagoscopy 4) during electroconsulsive therapy to prevent trauma. 5) diagonosis of myasthenia gravis.

14. 15 CENTRALLY ACTING MUSCLE RELAXANT CLASSIFICATION ( i ) Mephenesin congeners: Mephenesin , Chlorzoxazone , Methocarbamol . (ii) Benzodiazepines: Diazepam and others. (iii) GABA mimetic: Baclofen , Thiocolchicoside (iv) Central α 2 agonist: Tizanidine

15. 16 CENTRALLY ACTING MUSCLE RELAXANT They act on cerebrospinal axis without altering consciousness Selectively depress spinal and supraspinal polysynaptic reflexes Sedative property

16. USES Acute muscle spasm Torticollis , lumbago, backache, neuralgias Anxiety Spastic neurological disease Tetanus ECT Orthopedic manipulation 17

17. 18 DIRECTLY ACTING MUSCLE RELAXANT DANTROLENE: It acts on ryanodine receptor calcium channel and prevents calcium release from SR

18. The End