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Intro to Pharm

Muscle relaxants, anesthetics

QuestionAnswer
Spasticity exaggerated muscle stretch reflex or rapid lengthening of the muscle invoking a strong contraction in stretched muscle; supraspinal inhibition or control is lost because of a lesion in the spinal cord or brain; not a disease but part of pathologies such a
Spasm increased tension seen in skeletal muscles after injuries and inflammation; tension is involuntary, so patient is unable to relax; different from spasticity: involves input from pain receptors in damaged tissues which excite motor neurons to muscle buildi
Muscle spasm treating drugs baclofen, diazepam (centrally acting agents)
Centrally acting muscle relaxants: muscle spasm mechanism of action unknown, treatment always contains sedation, all drugs equipotent
Adverse effects of centrally acting muscle relaxants CNS depression, hepatic toxicity, physical dependence, all can be administered orally
Baclofen-muscle spasms derivative of GABA, inhibits motor neuron activity in the spinal cord, uses: paraplegia/quadriplegia, MS (not as much generalized weakness as dantrolene); less effective for stroke/cerebral palsy
adverse effects of baclofen: muscle spasms drowsiness, confusion & hallucinations, fatigue/nausea/dizziness/muscle weakness/headache
diazepam: muscle spasms increases GABA inhibition; use: cord lesions or cerebral palsy/acute low back strains
adverse effects of diazepam: muscle spasms sedation, tolerance, physical dependence
other central relaxants: muscle spasms use: adjuncts to other measures, incorporated into tablets with an analgesic, not effective for treatment of spasticity
Muscle spasticity treatment centrally acting agents: diazepam/baclofen; direct acting agent: dantrolene
Centrally acting agents: muscle spasticity Baclofen/diazepam treat spasticity, intrathecal baclofen
intrathecal baclofen administered to severe, intractable spasticity; need smaller doses/less side effects, catheter attached to a pump; decrease in rigidity/increase in muscle function; possibility of tolerance; need better pumps
Direct acting relaxants: muscle spasticity dantrolene
Dantrolene direct acting muscle relaxant: muscle spasticity; suppress release of calcium from sarcoplasmic reticulum resulting in the muscle losing ability to contract; minimal effects on smooth and cardiac muscles; overall function is reduced rather than improved;
Uses for dantrolene advanced MS; cerebral palsy; spinal cord injury
Side effects of dantrolene generalized muscle weakness
Other muscle relaxants Botulinum toxin (binds to presynaptic ACh receptors and prevents release of ACh; only temporary relief for spasms); Transdermal clonidine (antihypertensive agent; binds to CNS receptors-alpha2 & stimulates; unknown why works on spasticity; patch delivery)
treatment of muscle spasm drugs & therapy; relaxants often combined with analgesics: sedatives; no drug best
treatment of muscle spasticity drugs: increase motor function/decrease pain; side effects: sedation, muscle weakness, liver toxicity; reducing spasticity may effect person who relies on increased muscle tone for daily function; Baclofen: lesions on spinal cord; Diazepam: spinal and sup
Spasticity and Spasm concerns in rehab pts encounter often; complement thermal, electrotherapeutic, manual techniques; allows more ROM & stretching activities; sedation is problem; decrease in muscle tone/muscle weakness in antispasticity drugs (facilitate substitution of normal motor control for
General anesthetics produce unconsiousness & lack of responsiveness to all painful stimuli; two groups-inhalational & intravenous; analgesia: loss of sensibility to pain; anesthesia-loss of pain and all other senses
properties of an ideal anesthetic loss of consciousness & sensation; amnesia; muscle relaxation; inhibition of reflexes; low side effects; rapid onset, adjustable & rapid recovery
Balanced anesthesia combination of drugs to compensate for lack of ideal drug; ensure induction is smooth & rapid and analgesia & muscle relaxation are adequate; use short-acting barbituates for induction; use neuromuscular blocking agents for muscle relaxation; use opioids/
Stage I of anesthesia analgesia
stage II of anesthesia excitement: agitated/restless
stage III of anesthesia surgical anesthesia: deep respiration (want as rapidly as possible and maintain for duration of procedure)
stage IV of anesthesia medullary paralysis: all spontaneous respiration lost
inhalation anesthetics: Minimum Alveolar Concentration (MAC) minimum concentration of drug that will produce immobility in 50% patients exposed to painful stimuli; low MAC indicates high anesthetic potency; most anesthetics low MAC so only need low doses; only nitrous oxide has very high MAC-surgical anesthesia can
inhalation anesthetics pharmacokinetics anesthetic concentration depends on uptake from lungs & distribution
mechanism of action-inhalation anesthetic inhibit neuronal activity in CNS; exact mechanism unknown but 2 theories: general perturbation & specific receptor
general perturbation theory general effect on membrane structure & function by dissolving lipid bilayer
specific receptor theory membrane proteins rather than lipid bilayer are targeted
inhalation anesthetics: side effects respiratory & cardiac depression; sensitization of the heart to catecholamines (halothane specifically, develop dysrhythmias); malignant hyperthermia (genetic predisposition, muscle rigidity & elevated temp, inhalational anesthetic w/succinylcholine--trea
inhalational anesthetics: drug interactions Analgesics, CNS depressants, CNS stimulants
Adjuncts to inhalation anesthesia preanesthetic medications (reduction of anxiety-BDZ/Barb; production of perioperative amnesia; relief of pre & post op pain-opioids; anticholinergic drugs given to decrease risk of bradycardia); neuromuscular blocking agents-induce relaxation; postanesth
Classification of inhalational anesthetics volatile liquids-Halothane, Isoflurane; gases-nitrous oxide
Halothane highly potent, smooth and rapid induction, weak analgesic, low degree of muscle relaxation
Side effects of halothane hypotension, respiration depression, dysrhythmias, malignant hyperthermia, hepatoxicity (liver toxicity only in adults, therefore widely used in children)
Isoflurane most widely used inhalation anesthetic, high potency, induction is rapid & smooth & pts emerge rapidly; more effective than halothane as muscle relaxer
side effects of isoflurane hypotension, respiratory depression (does not cause myocardial depression or sensitize heart to catecholamines
Enflurane similar to halothane, wide spread use, may result in seizures
Desflurane identical to isoflurane, used for maintenance of anesthesia in adults and children and induction of anesthesia in adults
Sevoflurane relatively new similar to desflurane, pleasant odor-mask induction in children
Nitrous oxide low potency but high analgesic properties, impossible to produce surgical anesthesia, complement analgesic properties of primary anesthetic, reduces dose of primary anesthetic used, no serious adverse effects, does not precipitate malignant hyperthermia
intravenous anesthetics used alone or to supplement inhalation agents-permit dose of inhalation agent to be reduced, produce effects that cannot be achieved with inhalation agent alone
Short acting barbituate (thiopental) induction of anesthesia, weak analgesic/muscle relaxer; side effects: cardio/resp depression
Benzodiazepines produce unconsciousness & amnesia, normally use short acting barbs; diazepam-little muscle relax, no analgesia; midazolam-produces conscious sedation (endoscopic procedures)-dangerous cardio/resp effects
Propofol induction and maintenance of anesthesia; high risk of bacterial infection (mixture of egg lecithin)
Ketamine causes dissociate anesthesia; unpleasant psychological reactions may occur (hallucinations, disturbing dreams) but in children; used for children undergoing minor surgery and diagnostic procedures, changing of burn dressings; not in patients with history
Inhalation anesthetics: concern for rehab pts pt. may be woozy, nauseous, muscle weakness, bronchial secretions which may produce respiratory infections-implement respiratory hygiene
local anesthetics do not reduce consciousness but blunt sensation to limited area, suppress pain by blocking impulse conduction along axons (specifically block sodium channels), localized suppression
two classes of local anesthetics esters (procaine/novocain); amides (lidocaine/xylocaine)
local anesthetics: esters procaine/novocain: low incidence of allergic reactions; metabolized by plasma esterases
local anesthetics: amides lidocaine/xylocaine: very low incidence of allergic reactions; metabolized by hepatic enzymes
nonselective modifiers of neuronal function (so deliver to spectific area) block small nonmyelinated neurons more rapidly than large myelinated; lose perception of pain first, followed by in order perception of cold-->warmth-->touch-->deep pressure; drugs can block sensory and motor neurons
onset determined by molecular size/lipid solubility/tissue pH small size, high lipid solubility, low ionization cross rapidly; termination depends on above plus regional blood flow to carry away anesthetic; frequently used with vasoconstrictor (epi) to decrease local blood flow & delay systemic absorption (prolongs
Adverse effects of local anesthetics CNS excitation followed by depression, bradycardia/heart block/cardiac arrest/hypotension; allergic reactions-more likely with ester type; depress uterine contractions prolonging labor
procaine (novocain) ester-type; give by injection; given with epi to delay absorption; systemic toxicity is rare because rapidly converted to nontoxic products; use has declined
Lidocaine (xylocain) amide-type; widely used (topical/injection); more rapid/more intense/more prolonged anesthetic than procaine; combine with epi; CNS/cardio toxicity can result; used to treat dysrhythmias
Cocaine ester-type; excellent local anesthetic; topical administration for ear/nose/throat; causes intense vasoconstriction: do not give with EPI; CNS stimulant-psychological dependence; stimulates the heart and causes vasoconstriction; may result in hypertension
topical administration of local anesthetics relieve pain/itching/soreness, mucous membranes of nose/mouth/bronchi/urethra, hemorrhoids; possible systemic toxicity
injection administration of local anesthetics may result in severe systemic reactions; IV line in place to treat toxicity; monitor patient for cardio/respiratory function
concerns for local anesthetics with rehab pts produce long term improvements in motor function; ionto/phonophoresis; may receive CNS blockade through injection into spinal cord and thus have decreased sensation to thermal/electrical stimulation
Created by: mpost51