Muscle relaxants Flashcards
Hyper excitable skeletal muscle caused by an injury in the CNS; neurologic injury; including cord-related problems and injuries to the brain
Spasticity (seen in CP, MS, SCI, CVA)
Increased tension often seen in skeletal muscle after certain musculoskeletal injuries and inflammation; Nerve impingements, muscle strains, muscle overuse; Chemical or mechanical stimuli in the peripheral nervous system
Spasms
What are some symptoms you would see with spasticity?
- Increased tonic stretch reflexes
- Increased tone
- Muscle weakness
- Decreases in viscio-elastic properties of the muscle
What is the mechanism of action in spasticity?
- Loss of supra spinal inhibition of alpha and gamma motor neurons
- Leads to excitability of alpha motor neurons
What does pharmacology aim to alter in spasticity?
- Modify stretch reflex arc
2. Interfere directly with skeletal muscle contraction
What cycle can cause spasms?
pain-tension-pain cycle
What does pharmacology aim to alter in spasms?
Depress spinal “polysynaptic” reflex arc
What are the 3 main categories of drugs used for muscle spasms?
- Diazepam (Valium) - CNS depressant
- Polysynaptic inhibitors
- Dichlorodifluoromethane - topical treatment
Muscle spasm drug that increases the central inhibitory effects of gamma-aminobutyric acid (GABA); Has some sedative effects in the brain; ADRs = Hypotension, Rash, Muscle weakness, Ataxia, Incoordination, Somnolence, Euphoria, Respiratory depression, Fatigue; Can cause tolerance/physical dependence, withdrawal, and overdose
Diazepam (Valium)
What are some polysynaptic inhibitors?
- Carisoprodol (Soma)
- Chlorphenesin carbamate (Maolate)
- Chlorzoxazone (Paraflex)
- Cyclobenzaprine (Flexeril)
- Metaxalone (Skelaxin)
- Methocarbamol (Robaxin)
- Orphenadrine (Norflex)
Decrease [part of drug name] reflex activity in the brainstem;
Inhibiting these pathways cause a decrease in alpha motor neuron excitability and therefore cause relaxation of skeletal muscle; DO NOT WORK for spasticity; ADRs: Drowsiness, Dizziness, nausea, Lightheadedness, Vertigo, Ataxia, Headache, Long term or excessive use may cause tolerance and physical dependence, Fatal overdoses can occur
Polysynaptic inhibitors
What conditions are cautions for polysynaptic inhibitors?
- Patients with hyperthyroidism
- Patients with glaucoma
- Patients with urinary retention
- Enhances the effect of alcohol, barbiturates and other CNS depressants
Uses for managing pain and muscle spasms and myofascial pain; spray from origin to insertion of muscle; for trigger points
Dicholorfluoromethane
What drugs are used for spasticity?
- Baclofen (Lioresal) - GABA agonist
- Dantrolene (Tantrum) - acts on muscles
- Diazepam (Valium)
- Gabapentin (Neurontin)
- Tizanidine (Zanaflex)
Drug for spasticity that binds preferentially to GABA-B Receptors- inhibiting transmission within the spinal cord at specific synapses of the alpha motor neurons; ADRs: Transient drowsiness, Confusion and hallucinations, Fatigue, dizziness, muscle weakness, headache, Withdrawl symptoms
Baclofen
How is baclofen administered for patients with severe, intractable spasticity?
Intrathecal (subarachnoid) administration [no systemic effects, only small drug amount needed, requires surgical implant, complications include pump malfunction, catheter displacement, tolerance build up]
Impairs the release of calcium from the sarcoplasmic reticulum within the muscle cell during excitation; Severe spasticity, particularly where other drugs are not effective; Uses include Traumatic cord lesions, Advanced MS, Cerebral Palsy, CVA , Malignant Hyperthermia ; Not used for spasms caused by musculoskeletal injury; ADRs: Generalized muscle weakness, Hepatotoxicity , Fatal hepatitis, Drowsiness, dizziness, nausea, diarrhea
Dantrolene
Drug for muscle spasticity that decreases spasticity by raising the overall level of inhibition in the spinal cord, thereby decreasing excitation of the alpha motor neuron with subsequent skeletal muscle relaxation; ADRs: dizziness, sedation, fatigue, ataxia; also can be used for chronic pain
Gabapentin (neurontin)
Drug for muscle spasticity that is an Alpha 2 adrenergic agonist in the CNS, Stimulation of these receptors inhibits the firing of interneurons that relay information to alpha motor neurons; Used to relieve spasticity after a neurological injury; ADRs: Sedation, Dizziness, Dry mouth, Hypotension, Less generalized weakness when compared to baclofen and diazepam
Tizanidine (Zanaflex)
Local use for generalized spastic disorders (CP) or local spastic disorders (CVA); Permanently block the release of ACh; PT is done when the effects are working to enhance function and decrease symptoms when drug wears off
Botulinum toxin
What are benefits of muscle relaxants during PT?
Drugs will complement physical rehab; PTs can do more aggressive PT with pts, which leads to prevention of reinjury
How can muscle relaxants interfere with physical rehab?
- Motor control problems
- Functional decline for daily activities
- Decreased alertness
- Weakness
- Tolerance and physical dependence
What solutions can a PT use for ADRs of relaxants?
- Schedule PT at a time when sedative effects are minimal
2. Discuss with MD the generalized weakness implications
In a pt with spasticity, intensive PT is used to promote
normal physiological motor control
In a pt with spasms, intensive PT is used to improve
muscle strength, posture and flexibility, including proper body mechanics to decrease the need for the drugs
