Chapter 7 Pharmacology

• functions of the nervous system

  Receive stimuli and transmit information to the nerve centers to initiate appropriate responses
• 3 types of neurons

  sensory, motor, associative
• sensory


  carry impulses towards CNS
• motor


  carry impulses away from CNS
• associative


  carry impulses from neuron to neuron
• parts of neuron

  cell body, dendrites, axon, terminal end fibers, synapse, neurotransmitter
• cell body


  responsible for maintaining life of neuron (has nucleus)
• dendrites


  structures that receive impulses and conduct them towards cell body
• axon


  single process extending away from cell body and conducts impulses away from cell body towards muscle cells, glands, or other nerves
• terminal end fibers


  branching fibers that lead impulses away from axon and towards synapse
• synapse


  space between two neurons or between neuron and its receptor
• neurotransmitter


  chem substance allows impulse to move across synapse from one neuron to another. Different neurotransmitters for diff functions
• CNS (central nervous system)


  brain and spinal cord (interpret info sent by impulses sent from PNS system and return instructions through PNS for appropriate cellular actions)
• PNS (peripheral nervous system)


  sends impulses to CNS and receives instructions for cellular actions in return
• CSF (cerebrospinal fluid)


  cushions and nourishes CNS; clear and colorless fluid produced by special capillaries within the ventricles in the brain
• sympathetic nervous system


  Fight or flight; responsible for increased HR, RR, and blood flow to muscles; decreased blood flow to GI functions and causes pupillary dilation; releases acetylcholine, epinephrine, and norepinephrine
• parasympathetic nervous system


  Homeostatic system; returns HR, RR, and blood flow to normal level; also returns GI functions to normal and constricts pupils to normal size; releases acetylcholine
• Barbiturates


  drugs that are chem. Derivatives or barbituric acid and act as CNS depressants
• phenobarbital


  (barbiturate) long acting; controlled drug in dogs in cats; increase in liver enzymes; side effects are ataxia, drowsiness, liver famage, respiratory depression, pu/pd, and polyphagia
• pentobarbital


  (barbiturate) short acting; controlled drug, controls seizures from toxins and can be used for euthanasia in high doses (multiple uses: anesthetic, control seizures, euthanasia)
• zonisamide


  long acting; not barbiturate but in class of sulfonamides; anticonvulsant medication used to treat dogs and cats with epilepsy
• seizures

  periods of altered brain function due to recurrent abnormal electrical impulses; seizures are due to traumatic, idiopathic, infectious, toxic, and metabolic reasons
• benzodiazepines


  used as anticonvulsant, muscle relaxation, or to relieve anxiety
• diazepam (Valium)


  benzodiazepine; short acting; IV or rectally (only drug rectally); stops seizure-then switch to another med short acting (also an anesthetic)
• lorazepam (Ativan)


  benzodiazepine; lasts longer than diazepam; IN, IM, and buccal
• gabapentin (Neurontin)


  oral add-on anticonvulsant; contains xylitol and can cause toxicity in dogs; used in dogs with nerve pain; excreted by kidneys
• Phenothiazine derivatives

  acepromazine (Promace), chlorpromazine (Thorazine)
• acepromazine (Promace), chlorpromazine (Thorazine)


  (phenothiazine derivative) reversal is flumazenil; calms animals for PE, transport, used as preanesthetic agent, antiemetic, and prevents motion sickness; lowers threshold for seizures (controversial); adverse effects are hypotension, protrusion of third eyelid (nictating membrane)
• diazepam (Valium), Telazol (ketamine and Valium mixed), Versed, Klonopin


  (benzodiazepines) reversal is flumazenil; anticonvulsant, antianxiety agent, muscle relaxant while remaining alert; can be used as an appetite stimulant in cats; short term anesthesia when mixed with other drugs; not analgesic; side effect CNS excitement and weakness
• Alpha 2 agonists

  xylazine (Rompun, AnaSed, Gemini); dormosedan; dexdomitor
• xylazine (Rompun, AnaSed, Gemini)


  (alpha 2 agonist) reversal yohimbine (Yobine); analgesic, short term anesthesia with other drugs, emetic- especially in cats, used in horses for colic; side effects include cardiovascular effects, hypoventilation, and cyanosis
• Dormosedan


  (alpha 2 agonist) for horses only; better analgesia than xylazine; causes severe cardiovascular and respiratory side effects
• Dexdomitor


  (alpha 2 agonist) dogs and cats; reversal antiseden
• Opioids


  derived from poppy seed
• morphine sulfate


  (opioid) treats severe pain, preanesthetic, anesthetic; side effects (GI stimulation, severe respiratory depression); if given IV to cat or dog w/ no other drugs on board, will throw up immediately 1-2 times
• hydromorphone


  (opioid) 5-7x more potent than morphine; lasts 4h longer than morphine; less vomiting
• butorphanol (Torbugesic, Torbutrol, Torb)


  (opioid) potent antitussive, 2-5x more analgesia than morphine; analgesic and preanesthetic
• hydrocodone (Hycodan, Tussigon)


  (opioid) antitussive (in dogs); some behavioral problems
• fentanyl (Duragesic)


  (opioid) transdermal patch (tab, injectable); good for 72h; never cut patch
• M-99


  (opioid) used in zoo/exotic animals; analgesic effects 1000x more potent than morphine; possibly fatal to humans