Muscle Relaxants

Presented By:- Dr. Nilofar Rasheed(PT) MPT (Ortho) Asst. Professor Noida International University Muscle Relaxants: -

• Muscle relaxants are used to relieve muscle spasms which may result form some conditions which affect the nervous system.

• Skeletal muscles attach to the bones and are used for voluntarily movements of the body. Muscle spasms occur when a skeletal muscle contracts and does not relax. Muscle spasms are forceful and involuntary. A sustained muscle spasm is called a muscle cramp. • Medication helps the muscles to relax, which may also reduce pain and discomfort. Muscle relaxants

Affects skeletal muscle function

Decrease the muscle tone. used to improve symptoms such as muscle spasms, pain and hyperreflexia. Skeletal Muscle Relaxants: - Skeletal muscle relaxants are drugs that act peripherally at neuromuscular junction/ muscle fiber itself of centrally in the cerebrospinal axis to reduce muscle tone and / or cause paralysis.

Nondepolarizing (Competitive) blockers: - Mechanism of Action: - The site of action of both competitive and depolarizing blockers is the end plate of Skeletal muscle fibers. Non depolarizing Blockers

Bind with Ach receptor(Acetylcholine)

Produces ganglionic receptor

Blocks neuro muscular transmission

Hence. Decreases tone of muscle

Paralysis/ relaxation of muscle  Uses  Facilitate the surgery especially intra abdominal, intra thoracic surgeries.  Prolonged ventilation.  Endo tracheal intubation.

 Adverse effects.  Apnea  Muscle pain  Dizziness. Depolarizing blockers: - Mechanism Of Action: - Similar action to Ach, but longer acting. Depolarizing Blocker

Combine with nicotine receptors

Initial depolarization of motor end plate

Muscle twitching

Persistent depolarization

Relaxation

Directly Acting Muscle Relaxants: -

Dantrolene: - o It interference with release of Ca+ from it stores in Sk.Muscles(Sarcoplasmic reticulum) o Inhibit excitation-contraction coupling. Uses: -  UMN disorder  Hemiplegia  Paraplegia  Cerebral Palsy  Multiple Sclerosis  Malignant Hyperthermia  Neuroleptic Malignant syndrome Adverse Effects: -  Flushing  Dizziness  Drowsiness  Dysphagia  Muscular weakness  Sedation  Malaise  Diarrhoea  Liver Toxity Comparative features of centrally and peripherally acting muscle relaxants

Centrally acting Peripherally acting Decrease muscle tone Cause muscle paralysis, without reducing voluntary movements lost voluntary power Selectively inhibit Block neuromuscular polysynaptic reflexes in transmission CNS Cause some CNS depression No effect on CNS Given orally, Practically always given i.v. sometimes parenterally Used in chronic spastic Used for short-term purposes conditions, (surgical operations) acute muscle spasms, tetanus Centrally acting muscle relaxants: - Classification: - Class Example Mephenesin congeners Mephenesin Carisoprodol Chlorzoxazone Chlormezanone Methocarbamol Benzodiazepines Diazepam and others GABA mimetic Baclofen Thiocolchicoside

Central α2 agonist Tizanidine Baclofen- Oral/Intrathecal

GABA agonist at GABA B receptor increase K+ conductance Hyperpolarization of membrane SK. Mus. Relaxation • Also(-) release of substance P

• Uses • severe spasticity • Pain like multiple sclerosis • Pain like ALS (amyotropic lateral sclerosis) • spinal injuries Adverse effect: -  Drowsiness  Confusion  Seizure  Respiratory depression  Comma  Mental confusion  Weakness and ataxia  Serum transaminases may rise  Sudden withdrawal after chronic use may cause hallucinations  tachycardia and seizures. Centrally acting Mechanism Of Action: - e.g;Tizanidine: - Centrally acting Alpha 2 adrenergic agonist

Inhibits release of excitatory amino acids in the Spinal interneurons.

It re- in forces both pre- synaptic & Post- synaptic inhibition in the cord • It may facilitate the inhibitory transmitter glycine as well. Therapeutic Usages: -  Acute muscle spasms  Torticollis  Lumbago  Backache  Neuralgias  Anxiety and tension  Spastic neurological diseases  Tetanus  Electroconvulsive therapy  Orthopedic manipulations Adverse effect: -  Drowsiness  Hypotension  Dry Mouth  Asthenia  Night-time insomnia  Hallucinations.  Dose- dependent elevation of liver enzymes occurs.  Though no consistent effect on BP has been observed  It should be avoided in patients receiving antihypertensive, especially clonidine.