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Anesthesia > Preanesthetic medication > Flashcards

Preanesthetic medication Flashcards

1
Q

Reasons for premed

A

To calm or sedate an excited, frightened or viscous animal
To minimize adverse effects of concurrently administered drugs
To reduce the required dose of concurrently administered agents
To produce smoother anesthetic inductions and recoveries
To decrease pain and discomfort before, during, and after surgery
To produce muscle relaxation

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2
Q

Pre-emptive analgesia is and why to utilize it

A

To provide analgesia before tissue injury, including surgery (and after)
Reasons to utilize pre-emptive analgesia
More effective analgesia and takes less medication than treating pain that already exists
Limiting pain before it occurs allows lowering overall amount of anesthetic required and therefore decreases drug risks
Speeds up recovery times

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3
Q

Considerations for selection of preanesthetic protocol

A

Species and breed
Temperament
Patient history
Physical status of patient
Availability and compatibility of drugs
Route available in that patient (PO,IV,IM,SQ)
Comfort with specific drugs
Procedure
Facilities available

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4
Q

Administering Premedication:

A

In general, time to effect of preanesthetic:
30-40 min before induction of SQ
10-20 min before induction if IM
3-10 minutes if given IV
Effects will be more pronounced and faster
More pronounced side-effects
Often requires an IV catheter
Patient to be left in quiet for drugs to have full effect
Excited patients require a higher dose of drug for equivalent sedation

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5
Q

Assessing sedation

A

Parasympathetic signs
prolapsed 3rd eyelid, drooling, constricted pupils
Ataxia
do not leave unattended; anxiety
Recumbency
Decrease in HR, RR, (BP)
Certain drugs can relax inhibitions and animals can become aggressive or exhibit other unusual behaviours

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6
Q

Preanesthetic precautions

A

Overdose can result in sufficient CNS depression to cause death
In very sick animals, recommended doses can cause lethal overdose
Horses that develop ataxia as a result of sedation can become anxious and enter “fight or flight”
Brachycephalic breeds should be continuously monitored under sedation
Relaxation of the elongated soft palate can cause the airway to close

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7
Q

3 main groups of premedications and would you mix them

A

Anticholinergics
Tranquilizers and sedatives
Phenothiazines
Benzodiazepines
Alpha 2-adrenoceptor agonists (alpha2-agonists)
Opioids
Usually used in combination of 2 or more of the above drugs
DO NOT MIX TWO OR MORE DRUGS UNLESS YOU HAVE A RELIABLE EVIDENCE IT IS SAFE TO DO SO!!

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8
Q

Anticholinergics work on what system and are they controlled

A

PSN and non controlled drug

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9
Q

Indications of anticholinergics

A

To counter the parasympathetic effects of many of the other drugs used in balanced anesthesia
Prevent and treat bradycardia
Decrease salivary secretions arising from parasympathetic stimulation (aids in intubation)
Mydriasis (prevents rolling of the eyeball and opens pupil for eye surgeries)

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10
Q

Routes of admin for anticholinergics

A

Im, SQ, IV and IT (intertracial)

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11
Q

Major effects and adverse effects of anticholinergics

A

Prevention of bradycardia
Increased HR
Cardiac arrhythmias
Reduction and thickening of resp secretions
Bronchodilation
Mydriasis
Reduction of GI, salivary,, and lacrimal secretions
Inhibition of peristalsis - colic horses

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12
Q

Tranquillisers and sedatives work by and act on what system

A

Centrally-acting
Cause depression of the CNS

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13
Q

Are tranquilizers and sedatives part of a balanced anesthesia plan and why

A

Part of balanced anesthesia
Smoother induction
Allows decreased dose of general anaesthetic
Patients recovery faster

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14
Q

Are tranquilizers and sedatives controlled drugs

A

Many are controlled drugs
Controlled drugs and narcotic act
Record! For inventory and with each individual use
Practice standards: lock and key, strict record of use

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15
Q

Indications of tranquilizers and sedatives

A

Tranquilizers = reduces anxiety but does not necessarily decrease awareness and wakefulness
Sedative = causes reduced mental activity
The effects of these drugs often overlap because they produce both effects to some degree, to the terms tranquilizer and sedative are often used interchangeably

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16
Q

Different types of tranquilizers and sedatives

A

Phenothiazines
-Acepromazine
Benzodiazepines
-diazepam (Valium@)
-midazolam (Versed@)
Alpha2-adrenoceptor (alpha2-agonists)
-xylazine (Rompun@)
-dexmedetomidine (DexDomitor@)

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17
Q

Phenothiazines (tranquilizer and sedative) effects what system and is it controlled

A

Ex. acepromazine
Non-controlled (not technically Pr either)
Approved for horses, dogs and cats
Injectable and oral formulations
No reversal

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18
Q

major side effects and adverse effects of phenothiazines

A

Reduction of the seizure threshold
Tachycardia or bradycardia
Antiarrhythmic vasodilation
Hypotension
Antiemetic effects

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19
Q

Mechanism of action for phenothiazines

A

Blocks receptors in the basal ganglia→ CNS depression
Blocks alpha1 adrenergic receptors
Some antihistamine effects

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20
Q

Physiological effects of phenothiazines

A

Causes calming, reluctance to move and decreased interest in surroundings
Decreased spontaneous activity, ataxia
Vasodilation (due to blocking of alpha1-receptors
Suppressors chemoreceptor trigger zone (antiemetic)
Will slowly cross the placenta

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21
Q

Clinical use of phenothiazine

A

Anti-anxiety and sedation (relatively mild)
Chemical restraint ot ease handling
Travel
Decreased dose of general anesthetic
Eases induction and recovery
Blocks morphine-induced excitement in cat
Antispasmodic
Antiemetic (decreases vomiting when used together with hydromorphone as preanesthetic)

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22
Q

Common side effects of phenothiazines

A

Vasodilation (alpha1 receptor blockade); causes hypotension→ monitor BP
Hypothermia in small animals
Sequestering of RBCs in the spleen
Causes splenic enlargement and drops PVC
Caution in splenectomies, anemia
Overdose may cause rigidity or tremors
Ptosis, prolapsed 3rd eyelid in dogs and cats
Can cause aggression of excitement

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23
Q

Other considerations of phenothiazines

A

Bradycardia but less than many other agents
No analgesia
Antiemetic
Prevents histamine release and decreases allergic response
Worsens depressive effect of other drugs in the resp system
Metabolized by liver

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24
Q

Side effects specific to horses of phenothiazines

A

Penile prolapse
Facilitates sheath cleaning, examination
But can be irreversible
Caution in breeding stallions
Possible excitement, sweating, tachypnea

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25
Q

Relative contraindications of phenothiazine

A

Breeding stallions- penile prolapse
BOXERS- may exacerbate underlying arrhythmias
Also avoid in severely debilitated, neonates, geriatrics, preexisting hypotension (blood loss, shock, dehydration), CHF, liver disease, CRF
Related to vasodilation and resultant hypotension
Always use caution when sedating brachycephalic breeds

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26
Q

How to use acepromazine

A

Can also use alone for anti-anxiety and minor restraint
Used in combination with other drugs for pre-anesthesia
There is a mg/kg dose AND a maximum dose
Increasing the dose does NOT increase sedation but does increase hypotension due to peripheral vasodilation
Works better if not already excited; excitement can decrease the effect
Lasts 4-8 hours
Do not combine with dexmedetomidine
No reversal. If overdose, provide supportive care
Support BP-fluids
Increase the sympathetic response

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27
Q

Butyrophenones is what

A

Azaperone/Stresnil@
Drug class: butyrophenones (similar to phenothiazines)
Only used in pigs
Very unpredictable results in other species
Blocks dopamine and norepinephrine activity in the CNS

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28
Q

Clinical indications for azaperone

A

Decreases aggression/fighting during weaning and mixing
Premedication and sedation (castrations)
Antiemetic
Decreases malignant hyperthermia
Potentially fatal genetic condition; increased metabolic rate and muscle activity in response to isoflurane, transport/handling stress
Most commonly occurs in pigs

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29
Q

Benzodiazepines is/when to use/ is it controlled

A

Ex. diazepam (Valium@), midazolam (Versed@)
Controlled (schedule IV of the controlled drugs and substances act)
Most not labelled for veterinary use therefore an example of ELDU
Injectable and oral (tablets) formulas available

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30
Q

Major effects and adverse effects of benziodiazepines

A

Antianxiety and calming
Anticonvulsant activity
Disorientation and excitement in young, healthy dogs
Dysphoria and aggression in cats
Muscle fasciculation in horses
Ataxia in recumbency in large animals
Few cardiopulmonary effects
Skeletal muscle relaxation
No analgesia

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31
Q

Does benzodiazepines have a reversal agent

A

Reversal → flumazenil

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32
Q

Mechanism of action for benzodiazepines

A

Increase GABA levels in the brain
GABA is an inhibitory neurotransmitter

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33
Q

Indications of benzodiazepines

A

As part of balanced anaesthesia
Premed to smooth induction and recovery
Can combine with ketamine for induction
Other common indications
Antianxiety to sedation; behavioural modifier
Anticonvulsant for treating seizures
Skeletal muscle relaxant (including urethral relaxation)

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34
Q

benefits of benzodiazepines

A

Minimal CV effects at appropriate dose
Dose cause dose-dependent resp depression
Smoother induction and recovery
Decreases amount of inhalant GA required
Increase skeletal muscle relaxation

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35
Q

Is benzodiazepine reversable

A

Reversible drug class
In the event of overdose or adverse reaction, can give the reversal agent (aka antagonists or antidotes)

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36
Q

Precautions of benzodiazepines

A

Sedation is not always reliable when used alone in animals
Dysphoria/excitement can occur
May unmask latent aggression in some animals (animals lose inhibitions)

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37
Q

Precautions with horses on benzodiazepines

A

Muscle fasciculation
Weakness, ataxia
Do not give alone except for seizures in adults

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38
Q

Contraindications of benzodiazepines

A

AVOID in pregnancy/caesarean
Will cross the placenta
Causes similar to FLOPPY BABY SYNDROME
Skeletal muscle relaxation in the neonate
Asphyxiation form relaxation of resp muscle

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39
Q

Diazepam is what drug class and used on what

A

Benzodiazepine
Commonly used
Dog, cat, horse, pig

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40
Q

Clinical indications of diazepam

A

Anticonvulsant for emergency treatment of seizures
Antianxiety (noise phobias) at lower dose
Sedation in some patients at higher dose
Must be used in combination with other drugs in cats and horses (and some dogs) or may cause excitement
Skeletal muscle relaxant
Relaxes urethral sphincter (blocked cats and dogs)
Can mix with ketamine for induction (KetVal)

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41
Q

Indications of diazepam

A

Inexpensive
Can be administered by many routes:
IV solution- painful/unreliably absorbed if given IM/SQ
Can give intrarectal if seizing patient
Also available as oral tablets
Dose varies depending on the route
Lasts 30 min - 2h
May cause a prolonged hangover effect
Historically used as appetite stimulant in cats- doesn’t really work-risky

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42
Q

handling and storage of diazepam

A

Controlled drug
Not water soluble
Will form precipitate if mixed with other drugs
Never use if precipitate forms
Only exception is KETAMINE (KetVal)
Store IV solution in glass containers
Drug binds to plastic with time
Keep from light
Flush IV lines immediately after administering
Binds to plastic and will form precipitate if still present in line/verin when drug is administered

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43
Q

Adverse effects; contraindications of diazepam

A

Contradiction for caesarean
Floppy baby syndrome
Depressed, poor muscle tone, excessive sedation
Aggressive dogs
Can bring latent aggression
Using alone in horses
Excitement and ataxia
Cats
Can cause sudden liver failure- increase risk with increase doses
Therefore avoid use as an appetite stimulant

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44
Q

midazolam/Versed@ is what type of drug class and used when

A

Benzodiazepines
Very similar to diazepam
Easier to use, but more expensive

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45
Q

How is midazolam different from diazepam

A

Twice as potente
Shorter acting
Compatible with many agents as it is water soluble
Can give IM, SQ, IV
CANNOT use alone
Not used as anticonvulsant

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46
Q

Flumazenil is what drug class

A

Antagonsit

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47
Q

Flumazil works for what drugs

A

Reversal agent (aka antagonist) for benzodiazepines including diazepam and midazolam

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48
Q

How does flumazil work

A

Binds to and blocks GABA receptors
More attraction for the GABA receptor then the benzodiazepines
Therefore, knocks of any benzodiazepine drug already bound to the receptor
Little to no effect on its own
Solemn used because $$$$ and short duration of action of diazepam/midazolam

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49
Q

Is Alpha2 adrenergic agonists (tranquilizer and sedative) controlled

A

No

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50
Q

Alpha2 adrenergic agonists effects and adverse effects

A

Dose dependent sedation that can be profound
Analgesia
Agitation or aggression when touched
Reaction to loud noises
Muscle tremors in horses
Cattle often lie down
Initial hypertension, bradycardia, and pale MM followed by hypotension, decreased cardiac output, and a little further decrease in the heart rate
Severe decrease in heart rate, BP, cardiac output, and tissue perfusion especially when high doses are given
Respiratory depression that can be severe
Muscle relaxation
Vomiting in cats and dogs
Adverse GI effects (bloat and colic)
Hyperglycemia
Hypothermia
Increased urination
Premature parturition in cattle
Horses may sweat

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51
Q

Large animal apla2 adrenergic agonist

A

Xylazine (Rompun@)
Detomidine (Dormosedan@)
Romifidine (Sedivet@)

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52
Q

Small animal alpha2 adrenergic agonist

A

Dexmedetomidine (Dexodomitor@)

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53
Q

Is the drug class Alpd2 adrenergic agonist reversable

A

Yes

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54
Q

Mechanism of action of alpha2 adrenergic agonist

A

Drugs bind to alpha-2 adrenergic receptors
Activation of alpha 2 receptors causes inhibition of release of norepinephrine and dopamine
Decreases overall sympathetic response
Metabolized by the liver; excreted by the kidneys

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55
Q

Physiological effect of alpa2-recptor activation

A

Overall CNS depression
Decreased overall ability to respond to stimuli
This action is enhanced if given together with an opioid or other sedative or tranquilizer
Decreases sympathetic response
Bradycardia- consistent, immediate, significant; as low as 12 bpm in a large dog
Resp depression
Increases parasympathetic nervous system
Increased GI motility (except in ruminants)

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56
Q

Indications of alpha2 adrenergic agonist

A

Rapid and reversible sedation
Mild analgesia on own
Can be used for neuroleptanalgesia
Occurs when alpha-2 agonist is combined with an opioid and given at a fairly high dose
A state of lack of awareness associated with very heavy sedation combined with strong analgesia
Used for minor procedures e.g. suturing lacerations in horses
Centrally-mediated muscle relaxation

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57
Q

adverse effects of alpha 2 adrenergic agonist

A

Severe hypotension
Can hyperventilate on room air
Possible arrhythmias with some of the older drugs
Increased risk if given too fast IV
Increased risk if also given atropine
Ataxia
Cattle can become recumbent, decreased rumen motility, risk of bloat and may cause abortion
Horses can become reactive to stimuli if give alone- noise, touch
Emesis in cats

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58
Q

Why does alpha 2 adrenergic agonsit cause hypotension

A

Related to significant bradycardia
Decreased pulse, MM become very pale
Do not use with acepromazine in small animals

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59
Q

Why can animals hyperventilate on room air when under alpha 2 adrenergic agonist

A

Decreased RR and resp volume
Enhances the resp depressant effect of other sedatives and anesthetics
RESPIRATORY DISTRESS IN BRACHYCEPHALIC DOGS
Ruminant very sensitive to resp effects

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60
Q

Warning and contraindications of alpha2 adrenergic agonist

A

Avoid or use extreme caution in pediatrics, geriatric
Avoid if severely dehydrated, in shock, cardiovascular disease, severe resp disease, or severe renal disease
Avoid if advanced liver disease
Avoid or use extreme care with acepromazine
Acpreomazine→ severe hypotension from combination of bradycardia and vasodilation; will plummet the BP and there is no way to bring it back other then reversal
However it can be fail safe group IF you have reversal on hand
MONITOR! MONITOR! MONITOR!

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61
Q

Using alpha2 adrenergic agonists

A

IM (15-20 min onset), IV (1-3 min onset)
Duration of sedation is 30-60 min
Don’t give IV too fast or will enhance the resp and cardiac depression effects
When using IV, should “give to effect” only until desired degree of sedation is achieved
Avoid SQ
Very lipophilic; drug will bind to fat and absorption will be unpredictable (can severely delay effect)
Decreased effect if stressed or fearful

62
Q

Indications of xylazine

A

Equine and bovine
Premed
“Standing sedation”
-For castrations, wound repairs, caesareans
Sedates animal without becoming recumbent
Colic
-Excellent visceral analgesia
30 min of analgesia if given as an epidural
Part of “Triple Drip”
-Injectable GA, to be discussed with ketamine
Two concentrations 20mg/ml or 100mg/ml
-Lower concentration in cattle b/c of increased rep and GI effects
IV “to effect”
-IV has more pronounced heart and resp effects
IM
-Onset of action occurs 10-15 minutes after Im injection
-Duration of action is approx. 30 min
Epidural
-Visceral analgesia
Often combined with an opioid (ex. butorphanol) or valium for better sedation and longer duration

63
Q

Adverse effects of xylazine

A

Cattle require 1/10 of dose compared to horse
-Even at recommended dose can have severe resp effects, cause GI stasis (i.e., bloat) risk of aspiration pneumonia
Horses
-Sweating
-Ataxia, wide-based stance
-Horses can become excited if used alone
-Never given intra-arterial in horse; will cause excitement/seizure/collapse
-Avoid in neonatal foals as the lowered HR cannot maintain blood flow

64
Q

detomidine/Dosmesdan@ are used in what and what drug class

A

Alpha2 adrenergic agonist
labeled for horses

65
Q

detmoidine works by/for

A

Similar to xylazine
Visceral analgesia
Give slowly IV to effect
Can give alone or with opioid
Severe hypotension and bradycardia
Twice the duration and stronger sedation
Used for standing sedation
Never use with IV sulphonamides→ heart failure

66
Q

romifidine/Sedivet@ is used for and why

A

Labelled for horses
Similar to xylazine, detomidine
Fast acting, long lasting
Severe hypotension and bradycardia
Sedative or pre med
Can use at low dose
Anxiolytic with minimal ataxia

67
Q

dexmedetomidine/Dexdomitor@ is used for and when

A

Small animal
Sedation (60-90 min); analgesia (30 min)
Sedation
Hip rads, minor procedures (with local anesthetic), quills
Premed
Sedation and pre-emptive analgesia
On going sedation if given as CRI

68
Q

Indications of dexmedetomidine

A

Usually given in combination with opioid
Better analgesia
Better sedation
Dresses the mg/kg dose of dexmedetomidine required→ decreases adverse side effects
Most commonly with butorphanol or buprenorphine
Will see more resp depression is combined with hydromorphone

69
Q

Dosing of dexedetomidine

A

The label dose is 10x to 20x what is used in clinic
Label dose is intended for heavy sedation with dexmedetomidine alone
When combined with opioids and/or with balanced anesthesia, only use at 1/10 to 1/20 the labelled dose
Is also labelled for indication at higher doses (not usually done)
As animal size increases, the mg/kg dose decreases

70
Q

How to administer dexmedetomidine and how long does it work for

A

IM takes 15-20 min onset time
NEVER give SQ- drug deposits in fat and releases unpredictably
Give IV to effect
Dog only
Do NOT give to rapidly, can stop breathing
1-3 min onset
Can give ½ IM, wait 15 min, give remainder IV to effect

71
Q

Adverse effects of dexmedetomidine

A

Profound bradycardia and resp depression (much more noticeable in dogs)
Monitor HR and BP
HR will drop significantly; 16 (large K9), 40 (small K9)
Monitor BP and pulse strength
Monitor MM
Will be pale; should never be cyanotic
Monitor oxygenation
Extend neck
Place on flow-by 100% O2 if available
Place IV catheter
If in doubt, place ion IV fluid support

72
Q

Caution and contraindications of dexmedetomidine

A

Do NOT use with atropine
-Heart block, heart failure
Extreme caution of avoid with acepromazine
-Profound hypotension
Extreme caution when followed by isoflurane in cats
-Iso causes more extreme vasodilation then acepromazine
Avoid if hypotensive dehydrated, geriatric, debilitated

73
Q

Alpha2 antagonists is what type of drug

A

Reversal
Reversals have a greater affinity for receptor then the agonist drug

74
Q

Alpha-2 antagonist for LA

A

Yohimbine (Yobine®)

Tolazoline (Tolazine®)

75
Q

Alpha-2 antagonist for SA

A

Atipamezole (Antisedan®)

Designed so you give equal VOLUME as Dexdomitor® for complete reversal

76
Q

Alpha 2 antagonist works by

A

Effects specific to alpha2 agonist- does not affect other drugs
Reversal of the sedative, cardiovascular AND analgesic effects of the corresponding agent
Few adverse effects at clinical doses, but significant adverse effects if too much is given by increasing sympathetic tone
GI, neurologic, and cardiovascular effects
Excitement, muscle tremors, hypotension, tachycardia, salivation, vomiting, diarrhea

77
Q

Opioids work as

A

Analgesia
-Strongest analgesics available in vet med
Preanesthetic
-Pre-emptive analgesia – giving before pain occurs results in less post op analgesia required and shorter recovery times
-Sedation
-Decrease total dose of GA required
Anesthetic induction
-At higher doses, some opioids can produce unconsciousness (uncommon)

78
Q

What are opioids used for

A

Majority have wide margin of safety at therapeutic dose (Higher Potency → Lower Therapeutic Index)

79
Q

Where are opioids metabolized

A

Metabolized by liver with renal excretion, therefore
Caution in very young, very old, debilitated
Caution in very ill (including head trauma, shock, HBC)
Caution if respiratory system is compromised

80
Q

Are opioids controlled

A

Yes

81
Q

Neuroleptanalgesia is and how to induce it

A

A profound state of sedation and analgesia
Induced by simultaneous administration of an opioid and a sedative
Ex. Dexmedetomidine + hydromorphone; xylazine + fentanyl
Commonly given for minor procedures or indication
Causes CNS depression to state of borderline unconsciousness
Can be aroused by extreme stimulation, noise

82
Q

Routes of administration of opioids

A

IM
SQ
IV
PO
Rectal
Transdermal
Subarachnoid
Intraarticular (joints)
Epidural
Neurolepetangelasia , when given IV, must be done so slowly to avoid CNS stimulation

83
Q

Mode of action of opioids

A

Drugs work by binding to opioid receptors
Although opioid receptors found on neurons throughout the body, analgesic and sedative effects are primarily the result of their action on receptors located in the brain and spinal cord
Brain- sedation and analgesia
Spinal cord-analgesia
Smooth muscle of the rep tract, GI tract, urinary tract

84
Q

Major types of opioid receptors

A

Mu (μ)
Kappa (κ)
Delta (δ)

85
Q

Mu opioid receptor works for

A

Supraspinal analgesia
Moderate to severe pain
Sedation
Resp depression
Bradycardia
Miosis (mydriasis in cats)
Hypothermia (hyperthermia in cats)
Euphoria /dysphoria
GI stasis (constipation)
Urinary retention
CRTZ (chemoreceptor trigger zone) for vomiting
Antiemetic at the vomiting center

86
Q

Kappa opioid receptor works for

A

Spinal analgesia
Mild to moderate pain
Miosis
Mild sedation
Little resp depression
Diuresis

87
Q

Classes of opioids

A

Pure agnostic
Partial mu-agonist
Agonist-antagonist
Pure antagonists

88
Q

What determines the class the opioid is in

A

Opioids are placed into “classes” based on which receptor they bind and whether binding causes the receptor to be turned on (agonist), partially turned on (partial agonist) or turned off (antagonist)

89
Q

Pure agonists work by

A

Drugs bind to and turn on the mu-receptor
May also turn on kappa-receptor
Provides the best analgesia (treats moderate to severe pain)
Mu-antagonist provides the best analgesia. Drugs with a higher affinity for the mu-receptor provide more analgesia
Also produces sedation
Highest risk of addiction
Morphine, hydromorphone, oxymorphone, fentanyl, meperidine, hydrocodone, tramadol

90
Q

Pure agonists side effects

A

Side effects as listed for the mu receptor (resp depression, GI stasis, hypothermia, occasional hyperthermia in cats); analgesia and sedation are better if also has kappa activity

91
Q

Partial mu-agonsits work by

A

Binds to and partially activates the mu-receptor

92
Q

Partial mu-agonists physiological effect compared to pure agonists

A

Less analgesia
Less resp depression
Less GI stasis
Less euphoria
Less hypothermia

93
Q

When to use partial mu-agnosists

A

Indicated for slight to moderate pain
Also used to “partially” block the effects of a pure mu-agonist that is given at the same time; i.e., acts as a partial reversal
Buprenorphine (partial mu-agonist; kappa antagonist)

94
Q

Agonist-antogonist opioids work by

A

Simultaneously turns on kappa-receptor (kappa-agonist) while blocking mu-receptor (mu-antagonist)

95
Q

Physiological effects of agonist-antagonist opioids

A

Mild analgesia
Sedation
Less resp depression and less GI effects than the pure or partial agonists
May cause dysphoria

96
Q

When to use agonist-antagonist opioids

A

Can be used to “completely block” either mu-agonist or partial mu-agonist activity
Butorphanol (kappa-agonist; mu-antagonist)

97
Q

Pure antagonists work by

A

Binds to both mu-receptors and kappa-receptors but does not produce any activity
Effectively acts as a block
“Reversals”
Naloxone
Naltrexone
Direnorphine (M-50) is the reversal agent specifically created for etorphine (M-99)

98
Q

Major side effects of opioids

A

Resp depression
Most common cause of death in case of OD
Centrally-mediated; decreases RR and tidal volume
Also inhibits the CO2-drive that stimulates breathing
Ventilation should be monitored and O2 available
Bradycardia
Hypothermia in all species
Occasional hyperthermia in certain cats is due to a mu-receptor response especially hydromorphone and can be fatal if not treated
Caution using in patients with brain trauma or cerebral edema; can increase brain swelling
Sedation

99
Q

Non-life-threatening side effects of opioids

A

Vomiting
GI stasis (constipation)
Dysphoria, excitement, hallucinations, startle response in cats
Addiction

100
Q

Why does opioids induce vomiting

A

Activates the chemoreceptor trigger zone in the brain
Often with first dose of mu-agonists in healthy pain free animals
Can block/decrease with acepromazine or diazepam

101
Q

Why does opioids cause GI stasis

A

More likely with chronic use
Avoid or caution in colic, bloat, FB surgeries (enterotomies)

102
Q

Why does opioids cause addiction

A

Mu-receptor mediated
Receptor down-regulation means may need to increase dose or dosing frequency to manage chronic pain

103
Q

Variable side effects of opioids

A

Variable effects may or may not occur depending on the specific opioid, dosage, route of administration and species
Antitussive (codeine, hydrocodone, butorphanol; to treat cough)
Vomit (apomorphine; IM hydromorphone)
Diarrhea and flatulence
Miosis in dogs; mydriasis in cats and horses
Excitement, dysphoria, whine/bark (dogs), increased motor activity (horse), increased sensitivity to noise
Hypotension/hypertension
Changes in urination
Excess salivation
Panting in dogs
Hyperthermia in cats
Sweating in horses

104
Q

Pure mu agonists examples

A

Morphine
Fentanyl
Hydromorphone
Methadone
Meperidine
Sufentanil
Cerfentanil

105
Q

Indications of morphine

A

Mu and kappa agonist
Indications
“Opioid standard of reference)
All other opioids are compared to morphine
Mild to moderate sedation dose dependant
Analgesia for moderate to severe pain

106
Q

Routes and duration of morphine

A

IV, IM, SQ, PO, intra articular, epidural
Duration of action
3-4 hours

107
Q

Side effects of morphine

A

Excitement or dysphoria in cats, horses
Mydriasis in cats, horses
Drowsiness in dogs
Severe resp depression with high doses
Nausea/vomiting
GI stasis (oral form is worse)
Histamine release can cause systemic vasodilation

108
Q

Fentanyl indications and potency

A

Mu and kappa agonist
50-100x the potency of morphine
Indications
Neuroleptanalgesia
Induction
Analgesia (provided frequent administration)

109
Q

Routes and duration of action of fentanyl

A

IV bolus
CRI (preferred IV method)
Slow release transdermal patch
Epidural
Duration of action
1-2 min onset; 10 min duration of action IV
Usually CRI or slow release transdermal patch for analgesia

110
Q

Side effects of fentanyl

A

Defecation or constipation
Resp depression
Bradycardia
Hypothermia
Panting, drooling
Dysphoria, agitation
Sedation
Not approved for food animals

111
Q

Hydromorphone indications

A

Mu and kappa agonist
Indications
5-10x the potency of morphine
Moderate to severe pain (visceral and somatic)
Pre, peri and postoperative pain control
More sedation than morphine
Rarely used in large animals because of lack of info about efficacy or adverse side effects

112
Q

Duration of action by route for hydromophone

A

IV 1-2 hours
IM 2-4 hours in dogs, longer in cats
SQ up to 6-8h
Epidural 8 hrs

113
Q

Side effects of hydromorphone

A

Reliable emetic with first dose, especially if SQ/IM
Diarrhea with first dose; constipation with chronic use
Pant, drool
Mydriasis in cats and horse
Excitement /hallucinations in cats and horses

114
Q

Adverse effects of hydromorphone

A

Resp depression
Use with caution or contraindicated if severe resp disease
Most common cause of fatality
Bradycardia
Hypothermia in all species
Can cause occasional hyperthermia in cats which can be fatal
In the event of a severe adverse reaction, can partially reverse with buprenorphine or butorphanol; can completely reverse with naloxone, naltrexone

115
Q

methadone indications

A

Mu and kappa agonist
Indications
5-10x the potency of morphine
Moderate to severe pain (visceral and somatic)
Low incidence of vomiting (compared to morphine or hydromorphone); other side effects similar to other pure mu agonists
Excellent article summarising methadone released in the CVJ last year

116
Q

Duration of action for methadone

A

Duration of action ~4hrs
This is slightly longer than morphine and hydromorphone

117
Q

What can you use methadone on

A

Methadone is relatively new in canada
Currently only licensed for use in cats; however, it is licensed for use in cats and dogs on other areas (Australia, New Zealand countries within the UN and EU) as an analgesic and preanesthetic agent
Licensed in Canada: 0.5mg/kg IM in cats prior to spay or neuter.
Extra-label: commonly used 0.2-0.5mg/kg administered IV, IM or SC

118
Q

meperidine/Demerol@ indications

A

Mu and kappa agonist
Indications
1/10x morphine
Mild to moderate pain

119
Q

meperidine/Demerol@ route of action and duration

A

Routes
IM injection, NOT IV or SQ
Histamine release with IV use
Duration of action
30-90 min

120
Q

Side effects of meperidine

A

No vomiting or bradycardia
Use as premedication when no vomiting required

121
Q

Sufentanil works on what receptor

A

Super mu-agonist”
500-1000X the power of morphine
But shorter acting than fentanyl

122
Q

Indications of sufentanil

A

Intraoperative analgesia in dogs and cast as an infusion
Induction

123
Q

Carfentanil works on what receptor

A

“Super mu-agonist”
10,000-100,000X the power of morphine

124
Q

Indications of carfentanil

A

Wildlife capture and immobilization

125
Q

Why is carfentanil super dangerous for people

A

Potentially fatal if handler scratches/injects self
Use with extreme caution
Wear double gloves when handling closed bottle

126
Q

Reversal of carfentanil

A

Requires naltrexone for reversal
Draw up BEFORE handling carfentanil

127
Q

Partial mu agonists is

A

Buprenorphine
-Partial mu agonist, kappa antagonist

128
Q

Indications of buphenorphine

A

1/20x morphine
Mild to moderate pain
Less sedation
Onset of action ~30 min

129
Q

Routes and duration of action for bupernorphine

A

IV, IM, SQ, epidural or trans mucosal (in cats)
Place in the buccal cavity or sublingual and allow absorption through the oral mucosa
Will NOT work if swallowed
Duration of action
6-8 hours in dogs and cats
2 hrs in sheep

130
Q

Side effects of buprenorphine

A

Fewer side effects than hydromorphone due to partial mu-activity
Slightly dysphoria

131
Q

Reversal of buprenorphine

A

Higher affinity than naloxone, therefore requires much high doses or infusion of naloxone to reverse buprenorphine

132
Q

What drug is a Agonist- antagonist (kappa agonists, mu antagonist)

A

Butrophanol/Turbugesic@

133
Q

indications of butrophanol

A

½ to 1x morphine
Mild to moderate pain
Analgesia and sedation are via the kappa-receptor
Ex, colic
Sedation
Antitussive
Reversal of hydromorphone
SA (0.5mg/ml) and LA (10mg/ml) concentrations

134
Q

Routes used for butrophanol

A

IV, IM, SQ, PO

135
Q

Side effects of butrophanol

A

No mu-receptor mediated side effects
Less resp depression
No excitement
No GI stasis
No panting in dogs

136
Q

How does butrophanol work as a reversal

A

Binds to and blocks mu-receptor
Activation of kappa receptor produces mild to moderate analgesia and some sedation
If butorphanol and hydromorphone are both present, butorphanol will bind to the receptor because it has 30X the affinity for the receptor compared to hydromorphone. Result is to kick out the hydromorphone and/or prevent the hydromorphone from binding to the receptor

137
Q

Opioid antagonists (reversal) indication

A

Reversal of desirable and undesirable effects of opioid agonists, partial agonist, or agonist-antagonist including sedation and analgesia
CNS and resp depression

138
Q

Routes of admin for opioid antagonists

A

IM, slow IV

139
Q

major effects and adverse effects of opioid antagonsits

A

Reversal of desirable and undesirable effects
Sedation, dysphoria, panting, resp depression, hypotension, bradycardia, GI effects and analgesia
The action of opioid antagonists if often dramatic, causing patient to appear nearly unaffected shortly after administration

140
Q

Naxalone is what type or reversal

A

Pure antagonist

141
Q

Naloxone indications

A

Complete reversal of both mu and kappa agonists
Will lose all adverse effects and all analgesia
Dog, cat, horses, exotics, people
1 drop under tongue of neonates after C-section to reverse resp depression of opioid given to the mother

142
Q

Duration of action and time of onset of naloxone

A

Duration of action
30-40 min; will need to top up
Time of onset
2 min IV
Aggressive use can cause catecholamine related cardiac arrhythmias and vasoconstriction leading to pulmonary edema

143
Q

Naltrexone indications and duration of action

A

(pure antagonist)
Both mu and kappa antagonist
More potent than naloxone
Used to reverse carfentanil in wild life
Can be used intranasally
Duration of action
Long lasting (hours)

144
Q

Butorphanol/Torbugesic@ (Partial antagonist)

A

Kappa agonists, mu antagonist
Only blocks mu activity; adds to kappa activity
Not very strong reversal
Leaves sedation and some analgesia
Will reverse resp depression and hypo/hyperthermia

145
Q

What drugs are pure antagonist

A

Naloxone
* Naltrexone
* Diprenorphine (M-50) is the reversal agent specifically created for etorphine (M-99)

146
Q

What drugs are pure mu agonists

A

Morphine
Fentanyl
Hydromorphone
Methadone
Meperidine/demerol
Sufentanil
Cerfentanil

147
Q

What drugs are partial mu agonsits

A

Buprenorphine

148
Q

What drugs are kappa agonists and mu antagonist

A

Butorphanol/Turbugesic

149
Q

Side effects of Mu receptor opioid

A

Resp depression
Bradycardia
Miosis (mydriasis in cats)
Hypothermia (hyperthermia in cats)
Euphoria /dysphoria
GI stasis (constipation)
Urinary retention
CRTZ (chemoreceptor trigger zone) for vomiting
Antiemetic at the vomiting center

150
Q

Side effects of kappa receptor opioids

A

Miosis
Mild sedation
Little resp depression
Diuresis

Anesthesia (6 decks)

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