Unit 3_Pharm

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

Skeletal Muscle Relaxants and Anesthetics:

Skeletal Muscle Relaxants and Anesthetics

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Increased Muscle Tone: Spasticity vs Spasm Spasticity: injury to brain or spinal cord Results in muscle “stiffness” exaggerated stretch reflex Velocity dependent Loss of control by higher brain centers

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Increased Muscle Tone: Spasticity vs Spasm Spasm: orthopedic injury to muscle or peripheral nerve root Tonic contractions-excite a-motor neurons? - protective to joint, bone as compensation?

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Muscle Spasm Benzodiazepines - Diazepam (Valium) GABA mechanism Side effects: sedation, generalized weakness 2. Polysynaptic Inhibitors (polysynaptic implies interneurons involved in reflex) - generalized CNS depression? - inhibit 5-HT? Both classes produce muscle weakness as Side Effect

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants 1. Some Common Polysynaptic Inhibitors L=less frequent M=more freq. R=rare Drug drowsiness dizziness headache nausea/ vomiting Cardisoprodol (Soma) M L L L Chlorphenesin Carbamate (Maolate) L L R R Chlorzoxazone (Paraflex) M M L L Metaxalone (Skelaxin) M M M M Methocarbamol (Skelex) M M L L Orphenadrine ( Norflex ) L L L L

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity Baclofen - typically oral Mechanism of action: - Binds GABA B- inhibition of alpha motor neurons in spinal cord Side effects: - muscle weakness, fatigue, drowsiness - in CVA and elderly, confusion and hallucinations

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity Intrathecal Baclofen - severe spasticity - delivery to subarachnoid space - lower doses - less systemic effects - fewer hallucinations in CVA, elderly

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity 2. Diazepam (Valium) 3. Gabapentin ( Neurontin ) Mechanism of Action: inhibits alpha motor neuron mechansim unclear- not same receptors as GABA may block voltage gated Ca++ channels Side Effects: sedation, fatigue, dizziness, ataxia

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity 4. Tizanidine ( Zanaflex ) Mechanism of Action: Alpha 2 agonist Inhibits interneurons that are stimulatory to alpha motor neurons Side Effects: sedation, dizziness, dry mouth less generalized weakness than other relaxants less cardiac effects than clonidine

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity- 1. Botulinum Toxin Mechanism of Action: Destroys SNARE proteins at NMJ that help fuse vessicles Administration: Injection into site ~ 3 month intervals Side Effects: Respiratory depression Other Applications hyperactive bladder with CVA better fit of orthotics cosmetic

Skeletal Muscle Relaxants:

Skeletal Muscle Relaxants Drugs to Treat Spasticity- Direct Acting 1. Dantrolene Sodium ( Dantrium ) Mechanism of Action: Blocks release of Ca++ from SR Side Effects muscle weakness hepatotoxicity drowsiness, dizziness Other Applications: Malignant Hyperthermia

General Anesthetics:

General Anesthetics General Goals: - loss of consciousness and sensation - amnesia - skeletal muscle relaxation - inhibition of sensory and ANS reflexes - minimum toxicity - rapid onset and recovery

General Anesthetics:

General Anesthetics Stages of Anesthesia Analgesic stage: Loss of somatic sensation, but conscious Excitement stage: unconscious and amnesiac, but agitation and restlessness Surgical Anesthesia: regular, deep respiration Medullary Paralysis: loss of respiratory and cardiac control Want to get pt to stage 3 as fast as possible!

General Anesthetics:

General Anesthetics Anesthetics classified according to route of administration: IV - rapid onset, less control Inhaled- longer onset, better control Usually use combination!

General Anesthetics- IV:

General Anesthetics- IV IV Anesthetics- CNS depressants Benodiazepines - Diazepam (Valium), Lorazepem ( Ativan ) Barbiturates - Thiopental (truth serum) 3. Ketamine ( Ketalar )- dissociative anesthesia - for short procedures- inhibits NMDA 4. Opiates ( Fentanyl ) + Antipsych ( Droperidol ) -dissociative with or without loss of consciousness 5. Short acting hypnotics - Propofol ( Diprivan ) - will see often in trauma centers or ICU - GABA mechanism

General Anesthetics- Inhalation:

General Anesthetics- Inhalation Inhalation Anesthetics Gas or Volatile liquid mixed with air or O2 Endotrachael tube or mask Classes: Halogenated volatile liquids- Halothane Newer drugs- also volatile liquids- desflurane faster onset, recovery Gas anesthetic : Nitrous oxide shorter procedures

General Anesthetics- Inhalation:

General Anesthetics- Inhalation Mechanisms of Action: Inhibit neuronal activity in RAS (unconsciousness, amnesia) Inhibit neuronal activity in spinal cord (immobility, inhibit painful stimuli) Interferes with Na+ channel? GABA binding, ACH inhibition? Side Effects: Confusion, muscle weakness, Lethargy, respiratory depression

General Anesthetics- Inhalation:

General Anesthetics- Inhalation Pharmacokinetics: Lipid Soluble Widely distributed Stored in adipose slow release elderly affected Little metabolism of inhalation anesthetics Excretion of inhalation via lungs

General Anesthetics- Adjuvants:

General Anesthetics- Adjuvants PREOPERATIVE MEDICATIONS 1. Neuromuscular Junction (NMJ) Blockers Rationale: 1. Blocks spontaneous contractions 2. Intubation easier 3. Reduces amount of anesthetic 2 types: Non-depolarizing Depolarizing

General Anesthetics- Adjuvants:

General Anesthetics- Adjuvants PREOPERATIVE MEDICATIONS 1. Nondepolarizing agents ( Pancuronium , Tubocurrarine ) Block N receptors (comp. antagonists) 2. Depolarizing agents - Succinylcholine ( Anectine ) Bind N receptor and depolarize muscle Drug not readily inactivated by cholinesterase Muscle stays depolarized, no further stimulation Slow vs fast metabolizers Both result in muscle paralysis Both increase histamine release and affect lungs Can cause hyperkalemia , muscle pain, anaphylaxis

General Anesthetics- Adjuvants:

General Anesthetics- Adjuvants PREOPERATIVE MEDICATIONS Sedatives- opiates, benzodiazepins , barbiturates- depends on type of anesthesia Antihistamines- sedate, reduce vomiting Antacids - reduce risk of lung injury from aspiration Anti-inflammatory steroids - help prevent vomiting, pain

Local Anesthetics- the “caines”:

Local Anesthetics- the “ caines ” Block pain transmission in peripheral nerves Na channel blockers small diameter fibers most susceptible applications: 1. peripheral nerve pain 2. Post-surgical pain 3. bursitis 4. tendonitis 5. trigger points 6. reflex sympathetic dystrophy syndrome (RSDS) 7. Minor surgeries

Local Anesthetics:

Local Anesthetics Administration: Topical Transdermal (patch or iontophoresis ) Infiltration - diffuses to sensory nerve ending (suturing) Peripheral nerve block – close to nerve trunk (dentistry) Central block- epidural or spinal Sympathetic block – - in ganglia - Bier block in selected limb (esp. in RSDS ) May be administered with vasoconstrictor, opiate

Local Anesthetics:

Local Anesthetics Mechanism of Action: Have lipophilic and hydrophilic groups connected by intermediate chain - Terminal amine neutral in plasma, ionized in cell Enter axoplasm and block VG Na Channels

Local Anesthetics:

Local Anesthetics Side effects: 1. Drowsiness 2. Dizziness 3 Blurred vision 4. Slurred speech 5. Poor balance 6. Tingling around lips/mouth 7. arrhythmias 8. respiratory depression 9. seizure

authorStream Live Help