Muscle Pharmacology: Muscle Relaxants and Stimulants Flashcards
1
Q
Centrally-Acting Muscle Relaxants
A
Used For Muscle Spasm and Spasticity
- 2 groups that relax skeletal muscle
- 1 group- localized muscle spasm
- other groups-spasticity
- Produce effects through CNS
- except dantrolene (acts solely on the muscle)
- Groups are not interchangable
2
Q
Muscle Spasm
A
- Involuntary contraction of muscle or group of muscles
3
Q
Treatment: Muscle Spasm
A
- Physical:
- immobilization of affected muscle
- cold compresses
- whirlpool baths
- Physical Therapy
- Drug Therapy
- Analgesic anti-inflammatory (aspirin)
- Centrally Acting muscle relaxants
- Diazepam
- Tizanidine
4
Q
Centrally Acting Muscle Relaxants:
MOA
Therapeutic Use
A
- MOA: Unclear- might be from sedative properties of the drugs or presynatpic action
- Diazepam
- enhane effects of GABA
- Tizanidine
- agonist-presynaptic alpha2 receptor
- Diazepam
- Therapeutic use
- relieve local muscle spasm
- decrease local muscle pain
- increase range of motion
- no studies show one drug is better than another
5
Q
Centrally Acting Muscle Relaxants: Side Effects
A
- Generalized CNS depression
- Hepatic Toxicity
- Tizanidine (Zanaflex) & Metaxalone (Skelaxin)
- can cause damage
- Chlorzoxazone (paraflex)
- can cause hepatitis and necrosis
- Tizanidine (Zanaflex) & Metaxalone (Skelaxin)
- Physical Dependence
- Abstinence syndrome (addiction)
6
Q
Spasticity
A
- Movement disorder of CNS origin
- Common Cause:
- multiple sclerosis
- cerebral palsy
- Characteristics:
- Increased muscle tone
- Spasm
- Loss of dexterity
7
Q
Drugs for Spasticity
A
- Baclofen (Lioresal)
- acts in the CNS
- Diazepam (Valium)
- Acts in the CNS
- Dantrolene (Dantrium)
- acts directly on smooth muscle
8
Q
Baclofen
A
- Aka: Lioresal
- Acts in the Spinal Cord (CNS)
- Suppresses hyperactive reflexes
- MOA: Unknown
- may mimic th action of GABA on spinal neurons
- Therapeutic Uses:
- Multiple Sclerosis, spinal cord injury, cerebral palsy
- NOT with stroke
- Decreases flexor and extensor spasms
- Suppresses resistance to passive movement
- no direct effect on skeletal muscle
- Multiple Sclerosis, spinal cord injury, cerebral palsy
- Adverse Effects
- no antidote for overdose
- Gradual withdrawal over 1 to 2 weeks
- abrupt intrathecal withdrawal-rhabdomyolysis (destruction of skeletal muscle)
- CNS Depressant
- GI symptoms (Nausea, constipation)
- Urinary Retention
9
Q
Diazepam
A
- Aka Valium
- Member of the benzodiazepine family
- only one approvd to treat spasticity
- MOA
- acts in the CNS
- mimics action of GABA
- Adverse Effect:
- sedation
10
Q
Dantrolene
A
- aka Dantrium
- MOA:
- acts directly on skeletal muscle
- suppresses the release of calcium from the Sarcoplasmic reticulum (SR)
- Therapeutic uses:
- spasticity associated with multiple sclerosis, cerebral palsy, spinal cord injury
- Malignant hyperthermia
- fatal condition baused by combo of succinylchoine and general inhalation anesthetics
- Adverse effects
- hepatic toxicity
- muscle weakness
- drowsiness
- Diarrhea
- Acne-like rash
11
Q
Centrally Acting Muscle relaxants: Other agents
A
- Gapapentin (Neurontin) and Pregabalin (lyrica)
- antiepileptic drugs
- some promise
- Progabide (Gabrene)
- mimics action of GABA at both receptor populations
- not approved in US
- Glycine
- inhibitory amino acid neurotransmitter
- Idrocilamide (Talval) and Riluzole (Rilutek)
- glutamate antagonists
- might be useful in ALS
- Talval not available in US
12
Q
Neuromuscular Drugs: Types
A
- Non-depolarizing Antagonists
- Depolarizing Antagonists
13
Q
Non-depolarizing Neuromuscular Blocking Drugs
A
- d-Tubocurare;
- (-nium)
- pancuronium
- Vecuronium
- rapacuronium
- Rocuronium
- cisatracurium
- atracurium
- mivacurium
- Competitive inhibition of ACh binding at nAChR (Nm) receptor
- stabilizing blockade
- Rapid muscle weakness followed by flaccid paralysis
- Curare
- 1st in class
- least selective bc it also produces some ganglionic blockade and induces release of histamine
14
Q
Depolarizing Neuromuscular Blocking Drugs
A
- Acetylcholine
- pure agonist of nicotonic receptor
- Succinylcholine
- ideal bc composed of 2 Ach
- Nicotinic receptor requires 2 Ach
- Nicotine
- pure agonist of nicotinic receptor
15
Q
Depolarizing Neuromuscular Blocking Drugs: How does it work
A
- Acetylcholine, Succinylcholine and Nicotine
- inhibit the activation of the neuromuscule nicotinic receptor
- Similar to Desensitization
- Administer succinylcholine
- Muscle Fasciculations
- initial depolarization (muscle contraction) followed by increasing weakness–>flaccid paralysis
- Densensitization
- end plate is repolarized but not able to be activated by agonists
- Phase I block of voltage-gated channels will be enhanced by AChE inhibitors which will reverse late Phase II Block
