Clin med 2 Flashcards
Pharm
General classes of drugs based on therapeutic use Those used to reduce muscle excitability
Spasticity Muscle spasm
Skeletal muscle relaxants
what is the goal of skeletal muscle relaxants?
Goal is to decrease muscle excitability without limiting muscle function
Spasticity
(Hypertone) is ?
Occurs after a CNS injury or disease
Due to an exaggerated muscle stretch reflex
Is velocity dependent
Usually in antigravity muscles (biceps)
a Spasms?
-Increased muscle tension following injury and inflammation
-Due to an orthopedic injury
-Myogenic, does have a neuro component/time
-Continuous, tonic
Hypertone develops when there is:
-↓ in inhibition from cortex and inhibitory sp cord interneurons
-Following an Upper Motor Neuron lesion
-Spasticity – velocity dep hypertone, on the against gravity mm side of a joint
Muscle Spasm develops due to:
Electrolyte imbalance
Dehydration
Mm overuse
Mm strain
Has both a neurogenic and myogenic components when prolonged
what are the Muscle Relaxants for Hypertonicity OR Spasms
Baclofen – primarily used for hypertone
Tizanidine – poly synaptic inhibitor (within spinal cord)
Diazepam- poly synaptic inhibitor AND central acting
Dantrolene – acts directly on the muscle
Botox – acts at the NMJ
Muscle Tone Management
Mo = Motor neuron in Sp Cord
Ii = Inhibitory interneuron
Ie = Excitatory interneuron
NMJ = Neuromuscular Junction
Muscle Relaxant Agents –Polysynaptic inhibitors
-Polysynaptic inhibitors
Centrally acting
Mechanism of action is poorly understood
Can cause a general reduction in CNS activity
This may be the reason why the muscles tend to relax
-Commonly used agents
Diazepam
Carisoprodol, chlorphenesin carbamate, chlorzoxazone, cyclobenzaprine, metaxalone,
Methocarbamol, orphenadrine citrate
Muscle Tone Management - Baclofen
GABA-B agonist
+ hyperpolarization
↓s release of excitatory NT
↑neuronal inhibition
Baclofen
“Intrathecal Administration”
The Programmer
-Externally programmed via computer software
-Instructions transmitted through a “wand” by radio telemetry to the infusion pump
-Can be programmed for a continuous dose over 24 hours up to 12 specific dosages throughout the day
*Simple continuous
*Periodic Bolus
*Complex-Continuous
Average doses – 300- 1000mcg
Refill every 4 – 12 weeks
Baclofen
“Intrathecal Administration”
The Pump
*Surgically implanted SC in abdomen
*Stores & releases prescribed amounts of drug
*Holds 18 ml (3.5 teaspoons)
*Refilled q 1-5 months depending on pump size, concentration, and dose
Baclofen
“Intrathecal Administration”
The Catheter
*Small diameter, silicone rubber tube
*Travels from pump, under skin, to delivery site in spinal cord
*Catheter introduced below L3, advanced to T8-10
disadvantages of Intrathecal Pump
*Requires surgery to implant the pump
*Expensive
*Tubing can become disconnected or kinked
*Risks
-Infection
-Baclofen overdose
-Pump dysfunction
-Symptoms of withdrawal
Advantages of Intrathecal Pump
*Medicine is sent directly to the nerve cells
*Medicine dosage can be adjusted
*Less medication is needed, which reduces side effects.
*Reservoir can be easily refilled when needed
*Surgery is reversible
what are S&S of Intrathecal Pump
over dose
Somnolence
Drowsiness
Seizures
Respiratory Depression
Hypertonia
Loss of consciousness
Intrathecal Baclofen Candidates
*Moderate to severe hypertonicity
*Potential to be more independent with ADL’s
*Non-ambulatory with tone interfering with caregiving
*Pain or at risk for skeletal deformity
*Committed support system
*Over 4 y/o
*Respond to intrathecal test dose < 100 micrograms
*One year post TBI
Muscle Tone Management- Diazepam
↑s GABA’s central
inhib effect @ Ii
CNS depressant
Muscle Tone Management – Dantrolene (Dantrium
*Acts directly on mm
*An antagonist of the ryanodine receptor (Ca channel receptor in SR of skeletal mm)
Muscle Tone Management – Zanaflex (Tizanidine)
Central acting -2 agonist
↑inhib effects of Ii
Muscle Tone Management – Botulinum Toxin
*Prevents release of acetylcholine vesicles from presynaptic axon @ NMJ
-Toxin binds to presynaptic axon terminal
-Internalization of toxin
-Inhibition of NT release
*Administered IM in specific muscles
*Chemical denervation within days – lasts approx 3 months
Anti-Muscle Spasm Agents
Drug
Onset of action (min)
Duration of action (hrs)
*Carisoprodol (Soma)
onset 30 mins
duration 4 - 6hrs
*Chlorzoxazone (Paraflex, Parafon Forte)
onset Within 60 mins
duration 3 - 4hrs
*Cyclobenzaprine (Flexeril)
onset Within 60
duration 12 - 24 hrs
*Diazepam (Valium)
onset 15-45 min
variable
*Metaxalone (Skelaxin)
onset 60 min
duration 4 - 6 hrs
*Methocarbamol (Carbacot, Robaxin)
onset Within 30
duration 24 hrs
*Orphenadrine citrate (Antiflex, Norflex)
onset-Within 60
duration 12hrs
Clinical Implications – Muscle Relaxants
adverse reactions
*Generalized muscle weakness
*Decreased muscle tone
*Sedation
*Dizziness
*Ataxia
Clinical Implications – Muscle Relaxants
Effects interfering with rehabilitation
*Motor control problems
*Functional decline
*Decreased alertness
*Weakness
*Tolerance and physical dependence
What are side effects
constipation
dizziness
low blood pressure
dry mouth
allergic reactions
impaired thinking
heart problem