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