Sedatives / Tranquilizers Flashcards
Drugs acting on the CNS
Sedative & Tranquilizers - Alpha 2 agonists & antagonists - Opioids - Injectable anesthetics - Inhalant anesthetics
Tranquilizer aka..
Neuroleptic, anxiolytic
Tranquilizer effects
Induces state of behavioral change, anxiety relieved, patient is relaxed & aware of surroundings
Sedative
CNS depression & drowsiness, decreased awareness of surroundings
Hypnotic
Induces sleep
Narcotic
Induces stupor bordering general anesthesia
Local/Regional anesthesia
Loss of sensation to a circumscribed body area
General anesthesia
Drug-induced unconsciousness with controlled, reversible CNS depression & analgesia. Patient cannot be aroused. Sensory, motor and autonomic reflexes reduced
Dissociative anesthesia
Dissociate thalamacortic & limbic systems. Catatonic state with open eyes & swallowing reflexes remain functional. Skeletal muscles maintain tone
4 parts of pain pathway
Transduction - Transmission - Modulation - Perception
Transduction
Nociceptive Input (turn physical stimulus into electrical signal for nerves) - PGs, Substance P, K+, Bradykinin, increase peripheral sensitization (when light touch feels painful)
Transmission
Afferent nerve: A-delta fibers (sharp pain) & C fibers (dull pain)
Modulation
To spinal cord via Dorsal Horn - Enhanced/Diminished depending on neurotransmitters & drugs - “Spinal cord windup” at this level (sensitization of nerves)
Perception
In cerebral cortex - Experience/Be aware of the pain - Somatic=bones/muscles/joints
Excitatory neurotransmitters
Glutamate (NMDA receptor) & ACH (acetylcholine)
Inhibitory neurotransmitters
GABA - Glycine (spinal cord)
Neurotransmitters metabolized by MAO
MAO=Monoamine Oxidase - Dopamine, NE, 5-HT (serotonin), Histamine
Goals of sedative use
What is signalment of patient? What is temperament of patient? What is the goal of drug use? Medical conditions/other drugs to consider?
Phenothiazines -Drug list
Acepromazine - *Proclorperazine - *Chlorpromazine - *Trimeprazine w/prenisolone - Promethazine - Ethylisobutrazine - Triflupromazine
Phenothiazine uses
Sedative - Premed - Antiemetic - Antihistamine - Antipsychotic (human)
Phenothiazine mechanism
Block dopamine receptors in CNS!! (also- block H1/ A1/ ACH-muscarinic receptors)
Phenothiazine effects overview
Sedation - Some muscle relaxation - No analgesia - Hypotension & minimal effects on respiration
Phenothiazine Effects on CNS
Emotional quieting - Sedation - Decreased spontaneous motor activity
Which Phenothiazines have less of a sedative effect?
Prochlorperazine / Chlorpromazine
What can large doses of Phenothiazine cause
Extrapyramidal signs (rigidity, tremors, akinesia)
Other CNS mediated effects of Phenothiazine
Hypothermia (hypothalamus) - Antiemetic (CRTZ) - Hyperprolactinemia (hypothalamus)
Phenothiazine effects on ANS
Blocks Alpha-1 receptors - Weak anti-cholinergic (block M receptors)
Phenothiazine blocking Alpha 1
Vasodilation –> hypotension - “Epinephrine reversal” (Block A1, epinephrine still promoting vasodilation. It’s vasoconstrictive effects are blocked)
Phenothiazine anticholinergic efect
Not usually clinically significant - Decreased tear production in cats & rabbits
Phenothiazine CV effects
Hypotension - Bradycardia - Anti-arrhythmic
Which dog breed is more susceptible to Phenothiazine
Boxers sensitive to CV effects
Phenothiazine Respiratory effects
Minimal @ therapeutic doses (may decrease rate, not oxygenation) - Depression possible @high doses or used with opioids (&other respiratory depressants)
Phenothiazine effects at skeletal muscle
Moderate muscle relaxation
Phenothiazine other effects
Reduced hematocrit (splenic sequestration) - H1 antagonist/ Antihistamine - Reduced platelet function - ADH inhibition causing mild diuresis? - Hyperglycemia? - Hyperprolactinemia?
Phenothiazine reduced platelet function
In vitro hanges in platelet aggregation - Not demonstrated with acepromazine in healthy dogs in vivo
Phenothiazine Administration
IV, IM, SQ, PO
Phenothiazine PO
Oral bioavailability low (~20%)
Phenothiazine bound in plasma?
Highly protein bound, unclear clinical significance when % varies
Phenothiazine distribution
High Vd - well distributed, crosses BBB into CNS
Phenothiazine Metabolism
In liver
Phenothiazine excretion
Metabolites excreted in urine
Phenothiazine duration of action variables
Depends on route of admin, species, breed, etc
Phenothiazine clinical uses
Preanesthetic (usually with opioids) - Tranquilizer - Chemical restraint - Antiemesis (motion sickness) - Antihistamine
Which Phenothiazines are used for antiemesis?
Chlorpromazine & Prochlorperazine
Phenothiazine Cautions
Boxer dogs sensitive - Stallions get penile prolapse & paraphimosis - MDR1 mutants have more, prolonged sedation - Aggressive dogs startle more easily & CNS stimulation sometimes (reduced sedative effect in excited patients)
Phenothiazine vasodilation contraindications
DON’T use if vasodilation is contraindicated (Cardiac dz, hypovolemia, dehydration etc)
Phenothiazine Toxin contraindication
Tetanus, strychnine, etc because of extrapyramidal effects
Phenothiazine contraindication in cattle
Not approved in food animals, ruminal regurgitation sometimes seen
Phenothiazine Other contraindications
Liver disease - concurrent Epinephrine dosing - epidurals
Drug interactions with acepromazine
Epinephrine/ephedrine - Other CNS depressants - Metoclopramide (& others that cause extrapyrimidal signs) - Cholinesterase inhibitors - Emetics - Opiates - Misc. other drugs
Miscellaneous other drugs that interact with acepromazine
Dopamine, phenytoin, procaine, propanolol, quinidine, antacids, acetaminophen, antidiarrheals
Butyrophenones main action
Dopamine antagonist!!
Butyrophenone dopamine antagonist effects
Antipsychotics in human med - Declining use in vet med - Very similar to phenothiazines (vasodilation, minimal analgesia, paraphimosis in boars) - No approved products in US
Azaperone / Stresnil
Labeled for IM in UK swine (reduce aggression during group mixing, control sow aggression) A in BAM (darting wild ungulates)
BAM
Butorphanol- Azaperone - Medetomidine - used for darting wild ungulates
Haloperidol
To birds for feather picking
Benzodiazepines - 3 categories
Agonists - Antagonist - Inverse agonist
Benzodiazepine - Agonists
*Diazepam (valium) - *Midazolam - *Alprazolam (xanax) - Lorazepam (ativan) - Oxazepam - Clonazepam - *Zolazepam/Tiletamine (telazol)
Benzodiazepine - antagonist
Flumazenil (romazicon)
Benzodiazepine - Inverse agonist
B-carboline
Review! Agonist/Inverse Agonist / Antagonist
Agonist (binds & causes effect of usual ligand) - Inverse Agonist (binds & causes opposite effect of agonist) - Antagonist (binds and does nothing but block, “neutral agonist”)
Benzodiazepine mechanism of action
Bind site on GABAa receptors (Cl- channels) –> hyperpolarization of neurons
Benzodiazepine Overview of pharmacological effects
Some Sedation - Good Muscle relaxation - No Analgesia - Minimal Cardiorespiratory effects - Anticonvulsant - Appetite stimulant (unk mechanism)
Benzodiazepine CNS effects
Sedative-hypnotic (mild) - Anxiolytic - Centrally mediated muscle relaxation (supraspinal GABA) - Anticonvulsant -
Benzodiazepine CV & respiration effects
Minimal at therapeutic doses - Depression seen at larger doses
Benzodiazepine clinical uses
Anxiolytics/behavior modifier - Anticonvulsants (emergency seizure treatment) - Preanesthetic (in combo) - Sedation in ruminants - Muscle relaxation (anesthesia, urinary) - appetite stimulation
Benzodiazepine Administration types
Different products for different routes: Diazepam IV - Midazolam IM - Oral - Transmucosal/intranasal/rectal
Diazepam IV administration
Most common route - give slowly to avoid hypotension
Midazolam IM
Better IM choice than diazepam
Oral benzodiazepines
Generally good oral absorption - Diazepam=short duration - Alprazolam/lorazepam better
Problematic Diazepam administrations
Has slow & poor absorption IM & is painful from propylene glycol - Oral=short duration & hepatic necrosis in cats
What can oral diazepam cause in cats?
Hepatic necrosis
Transmucosal administration of diazepam
Decent bioavailability
Benzodiazepine Distribution
Lipid solube - wide distribution - cross BBB - protein bound
Benzodiazepine Metabolism
In liver into active metabolites
Benzodiazepine excretion
Primarily in urine
Benzodiazepine caution in cats
Hepatotoxicity with oral diazepam
Benzodiazepine caution in horses
Muscle fasciculations seen, ataxia @higher doses
Benzodiazepine benefits
Generally very safe bc lack of CV / respiratory depression (good in very young, old, sick)
Benzodiazepine paradoxical excitement
Sometimes seen - usually in combo with other animals or in fear-aggressive animals (disinhibition)
Benzodiazepine caution with diazepam injection
Propylene glycol causes pain IM - Hypotension with rapid IV injection - Hemolysis with large IV doses
Benzodiazepine caution in pregnancy
Maybe teratogenic (causes birth defects)
Benzodiazepine caution in liver/kidney disease
Altered metabolism / excretion
Benzodiazepine - Reversal
Flumazenil - Often unneccessary. B-carboline not used clinically
Most important phenothiazine for sedation
Acepromazine
Acepromazine + opioids = ?
Neuroleptanalgesia for chemical restraint - Or as pre-anesthetic
Acepromazine effects
Effective sedation - Some muscle relaxation - No analgesia
Acepromazine adverse effects
Hypotension - Always use with caution when hypotension is already a risk (epidurals)
What dog breed is sensitive to Acepromazine?
Boxers - Suffer worse cardiovascular effects
What happens to dogs with MDR1 mutations that are given Acepromazine
Have more profound clinical effects - Longer duration
What horrifying thing can happen to stallions on acepromazine?
May exhibit paraphimosis (can’t put foreskin back over the head) can lead to penile injury #gladIdon’thaveone
Trimeprazine Use & formulation
Antihistamine effects - Often combined with prednisolone “Temeril-P” - May see some sedative side effects, but not main use
Acepromazine & seizures
Once thought to lower seizure threshold, now thought to pre-dispose patients to them.
Butyrophenones Uses
Similar to phenothiazines - Human med: antipsychotic - Use in Vet Med declining
Butyrophenones - Name them
Azaperone - Droperidol - Haloperidol
Azaperone use
Swine, in UK - Reduce aggression
What is BAM?
Butorphanol-Azaperone-Medetomidine for darting wild ungulates
Haloperidol uses
Sometimes to control feather-picking in birds (psitticines)