CENTRAL Muscle Relaxants Flashcards
Guaifenesin
aka Glyceryl guaiacolate (GG)/Guaiacol glyceryl ether (GGE)
-central site of action: SPINAL CORD
-white powder dissolved in water, saline or dextrose for IV infusion
-muscle relaxant used during anesthesia in equine/bovine/swine
MOA
-specific MOA unknown
-depresses nerve impulses in spinal cord, brainstem, & subcortical areas of brain to cause centrally mediated generalized muscle relaxation, sedation, +/1 analgesia
PHYSIOLOGIC EFFECTS
-Resp-no significant effect on resp function (ie/ intercostal mm & diaphragm)
-Cardiovascular-transient hypotension seen (equines)
-but HR and CO minimally affected
PHARMACOKINETICS
-IV to horses & cattle
-often combined with anesthetic agents
-onset of action ~2min
-duration of action 10-20 min
-conjugated w/ glucuronic acid in liver
-metabolites excreted in urine
-crosses placental barrier (but no injury to fetus)
CLINICAL USES
-approved in horses, also used in cattle
-part of anesthetic protocol
–facilitates intubation
–smooth induction & recovery
–anesthetic sparing effect (reduces larger dose of other drug)
-Expectorant in horses?
CAUTIONS
-5% soln recommended
–>thrombophlebitis w/ 10% soln
–>Hemolysis with >10% soln (cattle>horses)
-may slightly precipitate out of soln @ 22C/72F or cooler (warm/agitate to resolubilize)
-Extralable in food animals
–>w/drawal times 3d meat, 48hr milk
DRUG INTERACTIONS
-commonly used with other drugs for LA anesthesia (“triple dip”)
-GG + a-2 agonist (xylazine or detomidine) +ketamine used for TIVA (total IV anesthesia)
-thiopental
-physostigmine-specific interaction unknown but listed as contraindicated by manufacturer. Consider caution w/ other anticholinesterases (neostigmine, etc)
Methocarbamol
-Central site of action: spinal cord
-carbamate guaifenesin (not metab to guaifenesin)
-exact MOA also unknown but likely works centrally
-approved for dogs, cats, horses
-available as oral tab, or inj
-typically IV or PO in dogs, cats; IV horses
-Generally NOT used with anesthesia
-used as adjunct for tx acute inflammatory & traumatic conditions of skeletal muscles & to reduce muscular spasms
-intervertebral disc dz
-functional urethral obstruction/urinary retention
-strychnine, metaldehyde, tetanus, permethrin poisoning
CAUTIONS
-used as IV can be irritating (avoid extravasation and DO NOT GIVE IV/SQ)
-sedation (2ndary effect, mild), weakness or ataxia possible
-salivation, emesis (V+)
-may darken urine
