Skeletal Muscle Relaxants (Central muscles relaxants (Diazepam (Uses:…
Skeletal Muscle Relaxants
Central muscles relaxants
Uses: Muscle spasm due to trauma, tension & over-exertion.
Adverse effects: Sedation or drowsiness (interferes in physiotherapy). ↑ the action of other CNS depressants.
Mechanism and action: ↑ the action of gamma amino-butyric acid (GABA), an inhibitory transmitter in CNS. * Control flexor and extensor spasms.
Tolerance and dependence can develop to its action.
Chlorzoxazone (usually combined with paracetamol/NSAIDS)
Acute muscle spasm due to injury.
Sprain and strains,
Low back pain.
Cervical root and disk syndrome.
Adverse effects: Hepatotoxic- Drowsiness- Urticaria,rash.
Baclofen ( A derivative of GABA)
Uses: Spasticity in spinal cord injury & multiple sclerosis. * Not suitable for Cerebral palsy & stroke.
Drowsiness & muscle weakness.
Sudden withdrawal can cause hallucination (auditory & visual), anxiety & tachycardia.
Mechanism and action:
Acts on the spinal cord.
↑ the release of excitatory transmitters in spinal cord. * Controls flexor and extensor spasms.
Direct muscle relaxants
Malignant hyperthermia ( of general anesthetics) In this condition sudden Ca release causes muscle contraction, lactic acid production & high grade fever,
Multiple sclerosis and cerebral palsy.
Adverse effects: Can cause muscle weakness, sedation & hepatitis.
Mechanism and action:
Inhibit release of Ca from sarcoplasmic reticulum.
↓ Ca release in muscle causes relaxation. * Cardiac and smooth muscle is very affected.
Tolerance does not develop to its action.
Mechanism and action
Tubocurarine & Succinylcholine: Both acts on neuro-muscular junction (NMJ)
Tubocurarine: Competitively block N-II receptors, prevents action of Ach & causes relaxation.
Succinylcholine: Depolarizes motor end-plate more persistently, muscle is unable to contract & is relaxed.
Muscle relaxation during surgical anesthesia.
Adjustment of dislocations of bones & joints (accidents).
Endotrachial intubation. * Crush injuries of chest, ECT, Tt. of poisioning (convulsant drugs).
Causes the release of histamine: ↓ BP & Bronchospasm ( should not be used in asthmatics)
a. Malignant hyperthermia ( when used with halothane). b. Apnea. c. Hyperkalemia.
Over dosage can relax diaphragm & cause dyspnea.
Acetylcholine release inhibitors
Mechanism and action: ↓ release of acetylcholine from motor nerve terminals. * Long acting & effect remains for few months.
Uses: Blephrospasm & cerebral palsy.