Download Muscle Relaxants

Muscle Relaxants
I. Central Acting
A.
Action: Work in the brain and spinal cord (upper levels of the CNS) to interfere
with the reflexes that cause muscle spasms, by lysing or destroying the spasm
(they are often referred to as spasmolytics)
B.
Adverse Effects:
Because they work in the CNS, there is a potential for CNS
depression
- GI- nausea, constipation, anorexia
- CV- hypoTN
- GU- urinary frequency, enuresis(bed wetting), feelings of urgency
- Ataxia (loss of muscle coordination)
- Use with caution! (Check BP, etc. before administering)
C.
Examples:
1. Prototype: Baclofen (Lioresal)
Indications: Alleviation of S&S of spacticity; used in spinal cord
injuries or diseases
Actions: GABA analog; inhibits spinal reflexes; CNS depression
2. Methocarbanol (Robasin)
Indications: Tetanus; parentaeral only for tetanus
3. Cyclobenzapine (Flexeril)
Indications: painful, acute conditions; 3 wk max usage; oral only
4. Diazepam (Valium)
Indications: antianxiety agent that also is effective for acute spasm and
pain
II. Direct Acting
A.
Action: Enter muscle fibers directly
B.
Examples:
1. Dantrolene (Dantrium)
Indications:
- Tx of spasticity directly affecting peripheral muscle contraction
associated with neuromuscular diseases
- Tx of malignant hyperthermia (intense muscle contraction resulting
in hyperpyrexia). There is a genetic predisposition for this. It
results in the hypermetabolism of skeletal muscles in surgery that
results in a dangerously high temp.
- Interferes with the release of intracellular calcium necessary to
initiate contractions.
Adverse Effects:
- CNS depression (drowsiness, fatigue, HA, confusion, vision
problems)
- GI- diarrhea, constipation, abd cramps
- Hepatic: fatal hepatitis
- GU: urinary frequency, enuresis, urgency, burning on urination
- Acne, hirsutism (excessive hair), photosensitivity, myalgia (muscle
aches)
Contraindications to Dantrolene:
Presence of allergy to drug
Spacticity that contributes to locomotion, upright position, or
increased function (those things would be lost if the spasticity was
blocked)
- Active hepatic disease
- Lactation
2. Botulinum Toxin Type A
- Approved by the FDA in 2002
- Temporarily improves the appearance of glabellar lines b/w the
eyebrows
- 4 units injected b/w the eyebrows every 3 months
- Adverse effects: HA, dizziness, flu-like symptoms, pain, droopy
eyelids, anaphylactic reactions
3. Botulinum toxin Type B
- Direct-acting skeletal muscle relaxant approved for neck pain
associated with cervical dystonia (causing distorted head position
and pain)
- IM injection directly into affected muscle
-
Anesthetics
I. General anesthetics
A.
Action: CNS depressants used to produce loss of pain sensation and
consciousness
B.
Goals: Analgesia (loss of pain perception); Unconsciousness (loss of awareness
of one’s surroundings), Amnesia; muscle relaxation; some cause temporary
paralysis (reversible)
C.
Risk Factors:
- CNS: stroke, seizures
- CV: CAD, HTN
- Respiratory: Ventilation; smokers have increased postop
complications x6
- Decreased renal and hepatic function
- Also: Weight, obesity, drug use, age (more risk with elderly)
- These drugs have an affinity for nerve tissue. The overtin-Meyer
theory states that the more lipid soluble a drug, the greater the
effect it will have, because nerve cell membranes and the blood
brain barrier have a high lipid content, therefore the drugs will
concentrate in those areas and decrease the senses
D.
Types: Barbituate, nonbarbituate, volatile liquids, gasses
1. Barbituates
A. Examples
1. Prototype: Thiopental (Pentothal)
- most widely used of the IV anesthetics
- rapid onset of action; ultrashort recovery period
- Indications: induction and maintenance of anesthesia; induction of
a hypnotic state
- Action: Depresses CNS to produce hypnosis and anesthesia w/o
analgesia
2. Methohexital (Brevital)
- rapid onset of action
- recovery period that is even more ultrashort (affective in seconds)
2. Non-barbituate
A. Examples
1. Prototype: Midazolam (Versed)
- Indications: sedation, anxiolysis, and amnesia prior to diagnostic,
therapeutic, or endoscopic procedures; induction of anesthesia;
continuous sedation of intubated patients
- Actions: Potentiates the effects of GABA; has little effect on
cortical function; exact mechanism of action is not understood
2. Ketamine(Ketalar) – dissociative (pt. Can’t remember); pt. Appears
awake but cannot feel pain
3. Propofol (Diprivan): used for short procedures. Increase in use b/c
there are not many SEs
4. Droperidol (Inapsine) – also has antiemetic effects
3. Anesthetic gases (volatile liquids are more popular than the gasses)
A. Examples
1. Prototype: Nitrous Oxide (blue cylinder)
- weakest, less toxic
2. Cyclopropane (orange cylinder)/Ether
- has a rapid onset of action and a rapid recovery
- not considered a good choice
3. Ethylene (red cylinder)
- less toxic than most of the other gasses, but leaves pt. With a
Haand unpleasant taste in their mouth
4. Volatile Liquids
A. Excreted through expiration over 24 hours (encourage deep breathing,
incentive spirometer, ambulation)
B. Examples
1. Prototype: Halothane (Fluothane)
- Indications: induction and maintenance of general anesthesia
- Actions: Depresses the CNS, causing anesthesia; relaces muscles
- Adverse effects: vomiting, decrased VS & hepatic toxicity
2. Sevoflurane (Ultane): newest, less adverse effects, rapid onset and
emergence, unstable at room temp; inhaled
3. Desfulrane (Suprane)
4. Enflurane (Ethrane)
5. Isoflurane
6. Methoxylflurane (Penthrane)
II. Local Anesthetics
A. Used to cause loss of pain sensation and feeling in a designated area of the body;
doesn’t produce systemic effects associated with general anesthetics (severe CNS
depression)
B. Methods of administration
- topical: cream, lotian, etc. (“-caine” drugs)
- infiltration: direct injection into tissues
- field block: all around area affected
-
nerve block: injection along nerves that run to and from the region,
i.e. epidural
Anxiolytic and Hypnotic Agents
I. Types
A. Anxiolytics (for anxiety: feeling of tension, nervousness, apprehension, or fear
involving unpleasant reactions to a stimulus)
B. Sedatives (to calm and make patients unaware of their environment)
C. Hypnotics (cause sleep/extreme sedation resulting in further CNS depression and
sleep)
II. Uses
1. Geriatric pts: comprise only 12% of our pop, but they consume 35-45% of
the sedative-hypnotic drugs
- for those in long-term care, benzos are prescribed first, and hypnotics are
used for no longer than 10 consecutive days in a 30 day period
2. Pediatric use: very limited, because paradoxical reactions have been
reported.
- always use lowest dose possible
III. Examples
1. Benzodiazepines
- widely used, lower fatality rates with toxicity and OD, lower
potential for abuse, less SE/adverse effects, fewer drug interactions
- Indications: anxiety disorders; alcohol w/drawal (Librium);
hyperexcitability and agitation; preop relief of anxiety and tension
(Xanax); seizure disorders. *not all benzos are used for all of these
indications – some are specific*
- Antidote to benzos: Flumazenil (Romazicon): inhibits the effects
of benzos at the GABA receptors; reverses sedation, coma,
respiratory depression; used IV only, rapid onset; monitor closesly
for rapid w/drawal
A. Examples of Benzos:
1. Prototype: Diazepam (Valium)
- Indications: anxiety disorders, DT’s, muscle relaxation, tetanus, status
epilepticus, preop relief of anxiety
- Actions: acts in the limbic system and reticular formation to potentiate
the effects of GABA (an inhibitory neurotransmitter); may act in the
spinal cord to produce muscle relaxation
- Long half life (20-80 hrs)
- commonly used for many years but now shorter acting drugs are more
often prescribed (like Ativan and Xanax)
- don’t mix valium IV with other drugs!
- administer orally if possible
- Adverse effects:
CNS: drowsiness, lethargy, confusion, dizziness, depression
GI: N/V, diarrhea, dry mouth, increased liver enzymes
CV: hypo or HTN, brady or tachycardia, palpitations
GU: hesitancy & retention, decreased libido, renal dysfunction
May lead to w/drawal syndrome if stopped abruptly
2. Lorazepam (Ativan)
3. Alprazolam (Xanax)
4. Clonazepam (Klonopin)
5. Chlordizepoxide (Librium)
2. Barbituates
I.
Action: general CNS depressant; sedation, hypnosis, anesthesia, and, in
extreme cases, coma
- inhibit neuronal impulse conduction in the ascending RAS
- depress the cerebral cortex
- depress motor output
- largely replaced by benzos b/c they are habit forming, have a
narrow therapeutic index, and numerous SE
II.
Indications: relief of S/S of anxiety, insomnia, preanesthesia, seizures
III.
Contraindications: allergy to any barbituate; hx of addiction to a
sedative or hypnotic drug; latent or manifest porphyria (rare hereditary
disease in which blood pigment Hgb is abnormally metabolized); marked
hepatic impairment or nephritis; respiratory distress or dysfunction;
pregnancy
IV.
Evaluation of pt. Receiving barbiturates
1. monitor pt. Response to the drug (alleviation of S&S of
anxiety, sleep, sedation, reduction in seizure activity)
2. monitor for adverse effects and dependence
3. evaluate effectiveness of teaching plan
4. monitor compliance w/ regimen
V.
Example
1. Prototype: Phenobarbital
- Indications: insomnia, tonic-clonic seizures and cortical focal
seizures, emergency control of certain acute convulsive episodes,
preanesthetic
- Actions: inhibits conduction in the ascending RAS; depresses
cerebral cortex; alters cerebellar function; depresses motor output;
AED activity
- Adverse effects:
CNS depression (drowsiness, lethargy, thinking abnormalities,
hallucinations, feeling of “hangover”
GI: N/V, diarrhea, epigastric pain
CV: decreased VS, syncope (fainting)
Hypersensitivity
- Long half life = 79 hrs.
3. Antihistamines
-
pre and post-op meds to decrease the need for narcotics
Examples
1. Promethazine (Phengran)
2. Diphenhydramine (Benadryl)
3. Hydroxyzine (Vistaril)
4. Buspirone (BuSpar)
-
reduces S&S of anxiety w/o severe CNS and adverse effects
newer drug w/ low abuse potential
5. Zolpidem (Ambien) and Zaleplon (Sonata)
- for short-term insomnia
- don’t disturb sleep quality but may have some next day
forgetfulness
- Sonata is known as a “rescue drug” – it is short acting, so only take
it if you are already having trouble sleeping. Lasts 4 hrs.
Psychotherapeutic Agents
I. Typical Antipsychotics
A. Prototype: Chlorpromazine (Thorazine)
1. Indications: manage psychotic disorders; relieve preop restlessness;
treat tetanus; acute intermittent porphyria; severe behavioral
problems in children; control hiccups, N&V
2. Actions: blocks postsynaptic DA receptors in the brain; depresses
parts of the brain involved in wakefulness and emesis
II. Atypical antipsychotics
A. Prototype: Clozapine (Clozaril)
1. Indications: manage severely ill schizophrenics unresponsive to
standard drugs; reduce the risk of recurrent suicidal behavior in
pts with schizophrenia or schizoaffective disorder
2. Actions: blocks DA and serotonin receptors; depresses the RAS;
anticholinergic; antihistamine; alpha adrenergic blocking
3. Newer drug: risperdal (risperidone): can cause cardiac arrest
Antiepileptic Agents
*Note: she said that we don’t need to know about each specific seizure type, AND we don’t
need to know exactly which seizure each drug is used for.*
I. Action: unclear (thought to act in two ways)…
1. Decrease responsiveness of neurons to stimuli by altering Na and other ions at cell
membrane, making the cell membrane less responsive
2. Enhance effects of GABA- stops or slows firing of neurons and decreases seizure
activity
II. Examples of antiepileptic agents
1. Hydantoins
A. Side Effects: hirsutism, constipation, drowsiness, confusion, dizziness, urine
may turn pink, gingival hyperplasia, increased blood glucose, decreased WBCs
and platelets, acne
B. Nursing implications: take w/ meals; with oral care use soft toothbrush; IV
ALONE with dilutent provided; use large vein and infuse slowly (25-50 mg over
1-5 min) b/c it is very irritating; monitor labs (blood glucose); watch for drugdrug interactions with antipsychotics, ASA, and anticoagulants
C. Examples
1. Phenytoin (Dilantin)
- treats tonic-clinic seizures and status epilepticus
- prevents and treats seizures after neurosurgery
- decreases Na influx across cell membranes
- has a narrow therapeutic index (5-20 mg/ml)
- takes 4-6 weeks for balance to be reached
2. Ethotoin (Peganone)
- controls tonic-clonic and myoclonic seizures
3. Fosphenytoin (Cerebyx)
- controls short-term status epilepticus; prevents seizures after
neurosurgery
2. Barbituates and barbituate-like drugs
A. Examples
1. Phenobarbital (Solfoton, Luminal): long half life
2. Primidone (Mysoline)
3. Mephobarbital (Mebaral): also an anxiolytic/hypnotic agent
3. Benzodiazepines
A. Examples
1. Prototype: Diazepam (Valium)
2. Clonazepam (Klonopin): more adverse effects, i.e. moodiness, aggression
Cholinergic/Parasympathetic Agents
I. Direct-acting cholingergic agonists
A. occupy receptor sites for Ach on the membranes of the effector cells of the
postganglionic cholinergic nerves, causing increased stimulation of the cholinergic
receptor (mimic Ach), but they are longer-lasting than Ach, and are resistant to Achesterase
B. Examples
1. Bethanechol (Duvoid, Urechoine):
a. indications: treats urinary retention, neurogenic bladder atony; reflux
esophagitis; stimulates gastric motility in paralytic ileus
b. actions: acts directly on cholinergic receptors to mimic the effects of Ach;
increases tone of detrusor muscles and causes emptying of the bladder;
increases GI muscle tone
c. given orally or Sub Q only
d. If given IV, pt will OD (Sludge)
e. Antidote: Atropine
2. Carbachol (Miostat) and Pilocarpine (Pilocar): induce miosis or pupil
constriction, relieve intraocular pressure of glaucoma, perform certain surgical
procedures
II. Indirect-acting cholinergic agonists
A. react with enzyme ACH-esterase and prevent it from breaking down the Ach that
was released from the nerve (it prolongs the effect of Ach).
B. Also called cholinesterase inhibitors
C. Increased stimulation of Ach receptor sites, prolonging the effect of Ach
D. Adverse effects: bradycardia, hypoTN, increased GI secretions and activity,
increased bladder tone, relaxation of GI genitourinary sphincters,
bronchoconstriction, pupil constriction
E. Used to treat: Myasthenia Gravis
1. Definition: chronic muscular disease caused by a defect in neuromuscular
transmission. It is an autoimmune disease (pts make antibodies to eh Ach receptors,
causing them to be destroyed)
2. Symptoms: progressive weakness and lack of muscle control w/ periodic acute
episodes; ptosis (drooping of the upper eyelid), double vision, difficulty chewing
and swallowing
3. Specific acetylcholinesterase inhibitors used to treat myasthenia gravis:
1. Prototype: Pyridostigmine (Regonol, mestinon): longer
duration of action than neostigmine; considered maintenance
drug of choice for MG
-Indications: myasthenia gravis. Also used as an antidote
after exposure to nerve gas
- Actions: reversible cholinesterase inhibitor that increased
the levels of ACh
- drug of choice of myasthenia gravis. Also improves muscle
strength and function by increasing the force of contraction
- antidote: atropine
- take AC (helps with chewing and swallowing)
2. Neostigmine (Prostigmine): strong influence at neuromuscular
junction
E.
Used to treat: Alzheimer’s disease
1. Definition: progressive disorder involving neural degerneration in the cortex,
that leads to a marked loss of memory and of the ability to carry on ADLs.
Cause is not yet known, but there is a progressive loss of ACh-producing
neurons and their target neurons
2. Specific acetylcholinesterase inhibitors used to treat AD
1. Prototype: Donepezil (Aricept)
- Indications: tx of mild to mod. AD
- Actions: reversivle cholinesterase inhibitor that causes elevated
ACh levels in the cortex, which slows the neuronal degradation
- Long half life (70 hrs)
2. Tacrine (Cognex): 1st drug that treated AD
3. Galantamine (Reminyl): used to stop progression of AD
4. Rivastigmine (Exelon): available in solution for swallowing ease
III. Anticholinergic Agents
A. Action: block the effects of ACh; also called parasympatholytic agents b/c they lyse
or block effects of the parasympathetic nervous system. Block mainly the
muscarinic effectors in the PNS. Compete with ACH for the muscarinic ACH
receptor sites; do NOT block nicotinic receptors
B. Uses: decrease GI activity and secretions (need to encourage fluids to prevent
constipation); decrease parasympathetic activities to allow the sympathetic system
to become more dominant (need to monitor blood pressure and pulse); widespread
effects on body limit their clinical value.
C. Better drugs are available now. There is not too much clinical value b/c of adverse
effects.
D. Derived from the plant belladonna
E. Examples of anticholinergic agents
1. Prototype: Atropine
- blocks parasympathetic effects in many situations
- depresses salivation and bronchial secretions
- dilates bronchi
- inhibits vagal responses in the heart – inc. HR
- relaxes the GI and GY tracts (antispasmodic)
- Inhibits GI secretions
- Causes mydriasis (dilated pupils), inc. intraocular pressure
- Causes cycloplegia (paralysis of ciliary muscles)
- Readily absorbed (can be given orally)
- Adverse effects: blurred vision, confusion, delusions, photophobia,
palpitations, tachycardia, dry mouth, altered taste perception,
urinary hesitancy and retention, decreased sweating, predisposition
to heat prostration
3. Tolterodine (Detrol)
4. Oxybutin (Ditropan)
5. Scopolamine (Hyoscine): treats motion sickness, preop amnesia
6. Propantheline (Pro-Banthine): adjunct tx for ulcers
F.
Anticholinergics are used to treat Parkinson’s disease (but they are not as
effective as those that increase DA). Only minimize symptoms. Must cross
blood brain barrier to treat PD. Early on they are used alone, and later in
combo.
1. Prototype: Biperiden (Akineton)
-Indications: adjunctive therapy of parkinsonism; relieves EPS symptoms
- Actions: Acts in CNS, returning balance to the basal ganglia and reducing
the severity of rigidity, akinesia, and tremors
- SE: confusion, dry mouth
2. Benztropine (Cogentin)- used in elderly who can’t tolerate artane
3. Trihexyphenidyl (Artane) – most frequenty used
G.
Dopaminergic drugs are also used to treat parkinsons (not anticholinergics, just
putting this here b/c it relates to treatment of parkinsonism)
1. Action: increase levels of DA in substantia nigra, and directly stimulates the
receptors in that area; enhance neurotransmission of DA
2. Indications; relief of S&S of idiopathic parkinson’s disease. Only work of
there are enough intact neurons to respond
3. nursing implications: give with food, avoid foods high in protein or vit B6
b/c they interfere w/ absorption. Divide foods high in protein into several
meals.; monitor hepatic, renal, hematological tests periodically
4. Examples:
1. Prototype: Levodopa (Dopar)
- Action: precursor of DA, crosses blood brain barrier, where it is
converted to DA and acts as a replacement. Only effective for 2-5
years
- Only 1% actually gets converted, therefore you increase doses and
subsequently side effects as well.
If you abruptly DC: NMS
Sometimes need a “drug holiday”, when S&S return, stay in
hospital, then re-start the drug
2. Carbidopa-levodopa (Sinemet)
- combo of levodopa and carbidopa as a fixed dose combo drug
- carbidopa decreases the amount of levodopa needed to reach a
therapeutic level in the brain, therefore the dosage of levodopa can
be decreased, reducing adverse side effects (ortho HypoTN, dry
mouth, fatigue)
-
Adrenergic/Sympathomimetic Agents (mimic sympathetic nervous system)
I. Sympathetic nervous system receptors:
1. Alpha 1 receptors: vasoconstriction, increase peripheral resistance, raise
blood rpessure, decrease nasal congestion; pupil dilation; contracts urinary
bladder and GI sphincters
2. Alpha 2 receptors: prevent further release of Norepi (antiadrenergic effect!);
help moderate insulin release stimulate by sympathetic nervous system
stimulation
3. Beta 1 receptors: increase myocardial activity and HR; increase breakdown
of fat for energy in peripheral tissues
4. Beta 2 receptors: vasodilation; dilates bronchi; increases muscle and liver
breaddown of glycogen and increase release of glucagons; relaxes uterine
smoothe muscle
II. Alpha and Beta Adrenergic Agonists
A. Examples:
1. Prototype: Dopamine (Inotropin): drug of choice for shock. (corrects
hemodynamic imbalances) Increased renal perfusion
Action: acts directly by release of norepi from sympathetic nerve terminals.
In low doses, it mediates dilation of vessels in the kidneys to maintain renal
perfusion. In higher doses: increase CO and BP
2. Dobutamine (Dobutrex): treats CHF
3. Norepinephrine (Levophed) – vasoconstrictor
4. Epinephrine (Adrenalin, Sus-Prhin): treats shock, glaucoma, prolongs effects
of regional anesthetic, tx of bronchospasm
5. Ephedra: used for weight loss. Associated with sudden death
B. Contraindications
1. pheocrhromocytoma (tumor of adrenal cortex that increase norepi and epi,
therefore cause high BP and HA)
2. tachyarrhythmias or V-fib
3. hypovolemia
4. halogenated hydrocarbon general anesthetics
5. caution should be used with PVD
III. Alpha-Specific Adrenergic agonists
A. drugs that bind primarily to alpha receptors rather than beta receptors
B. Examples
1. Clonidine (Catapres): used for htn, pain, to ease opiate w/drawal
2. Phenylephrine (Neo-synephrine)
3. pseudoephedrine (Sudafed): decrease swelling and congestion w/ allergies
IV. Beta specific adrenergic agonists
A. Examples
1. Isoproterenol (Isuprel)
Effects: increased heart rate (chronotropic), conductivity (dromotropic),
contractility (inotropic), causes bronchodilation, increased blood flow to
skeletal muscles and splanchnic beds; relaxes uterus
- absorption best by injection or aerosol
- stimulates beta 1 (heart) and beta 2 (bronchi) receptors
- treats shock, cardiac standstill, heart block, prevents bronchospasm
during anesthesia, inhaled to treat bronchospasm
V. Adrenergic Blocking Agents “Sympatholytic” b/c they block effects of SNS
A. Alpha and Beta adrenergic blocking agents:
1. Action: syppress pathological responses to activity, stress, or
other stimuli by preventing norepi (decrease SNS activity, i.e.
decrease BP)
*she said not to memorize examples of these*
B. Alpha-adrenergic blocking agent
1. Prototype: Phentolamine (Regitine)
- manages severe HTN caused by pheochromocytoma
- prevents cell death with IV infiltration of norepi or levophed
- blocks alpha 1 and 2 receptors
C. Alpha 1 selective adrenergic blocking agents
1. not frequently used – maybe for benign prostatic hypertrophy (don’t
memorize examples)
D. Beta-adrenergic blocking agents
1. treat cardiovascular problems: HTN, angina, migraine HA, prevent
reinfarction after an MI
2. Block beta 1 and 2 receptors (nonselective) = bronchioles and blood vessels
affected
3. Adverse effects: GI upset, SOB, bronchospasm, bradycardia, orthostatic
HypoTN, loss of libido, impotence, hypoglycemia
4. Example
A. Prototype: Propranolol (Inderal)
1. treats HTN, (don’t need to memorize the rest)
2. decreases oxygen demand, myocardial contractility, HR and
BP
E. Beta 1 selective adrenergic blocking agents
1. advantage is that they don’t usually block beta 2, including the
sympathetic bronchodilation, therefore it is preferred for
patients who have asthma, COPD, or seasonal or allergic
rhinitis (respiratory issues)
2. used for HTN, angina, some arrhythmias