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Flashcards in Premedication Drugs Deck (89):
1

Purposes of premedication

1. Sedation, analgesia
2. Anesthetic sparing effect
3. Reduction of stress and catecholamine release
4. Redution of O2 demand
5. Increased safety for animals and staff
6. Decrease parasympathetic tone

2

Drugs classes used in premedication

1. Anticholinergics
2. Alpha 2 agonists
3. Phenothiazines and butyrophenones
4. Benzodiazepines
5. Opioids
6. Antihistamines and antibiotics

3

MOA Anticholinergics

Inhibit parasympathetic nervous system
Antagonize muscarinic acetylcholine receptors

4

Anticholinergic drugs

Atropine and glycopyrrolate

5

Atropine

Lipid soluble
Absorbed well IM/SC/PO
Crosses BBB and placenta

Dose: 0.01-0.04 mg/kg IV

6

Glycopyrrolate

Water soluble
Absorbed slowly IM/SC/PO
Does not cross BBB and placenta

Slower than atropine, half the dosage

7

Indications for Anticholinergics

Need for increasing the heart rate (opioid induced or reflex bradycardia)
Need for decreasing salivation and bronchial secretions

8

Contraindications for Anticholinergics

-Tachycardia
-Hyperthyroidism
-Most heart diseases
-Narrow angle glaucoma

9

Cardiovascular side effects of Anticholinergics

1. Second degree AV block (bradycardia and cardiac arrect)
2. Tachycardia
3. Hypertension

10

What part of the heart do Anticholinergics effect?

SA node particularly
AV node is weakly effected

11

Medetomidine/Atropine disadvantages

Vasoconstriction, tachycardia, hypertension

12

Other effects of anticholinergics

1. Relaxes lower esophageal sphincter
2. Mydriasis
3. Bronchodilation
4. Dries airway secretions
5. intestinal paralysis
6. CNS toxicity

13

What drug treats anticholinergic CNS toxicity?

Physostigmine

14

Which Anticholinergic is preferred in rabbits?

Glycopyrrolate

Atropine is broken down too quickly

15

Which class has the strongest available sedative ability?

Alpha-2 Agonists

16

Do Alpha-2 agonists have specific antagonists?

Yes

17

MOA: Alpha-2 agonists

Competitive agonist of alpha-2 receptor (suppress NE release)

18

Location of alpha-2 receptors

1. CNS presynaptic membrane
2. Postsynaptic membrane
3. Extra-synaptic sites

19

Alpha-2 agonist presynaptic effects

1. Sedation
2. Analgesia
3. Reduction of sympathetic outflow from brain
4. Reduction of stress response

20

Alpha-2 agonist postsynaptic effects

Vasoconstriction of arteries and veins

21

Alpha-2 agonist extra synaptic effects

1. Inhibition of lipolysis
2. Inhibition of insulin release- hyperglycemia
3. Natural ligand with Epinepherine
4. Interaction with stress response

22

Alpha-2 agonist CNS effects

1. Species specific sedative (weak in pigs)
2. Some analgesia- synergism with opioids
3. Muscle relaxation

23

Alpha-2 agonist Cardiovascular effects

1. Strong vasoconstriction- high SVR and BP
2. Reflex bradycardia- low CO and tissue perfusion
3. May develop hypotension

24

Should alpha-2 agonists be used with atropine?

No- reflex bradycardia does not need to be treated

25

Alpha-2 agonist Respiratory effects

1. Mild respiratory depression (decreased RR)
2. Increase in tidal volume
3. Increased upper airway resistance
4. V/Q mismatch in horses and ruminants- decreased PaO2
5. Bronchoconstriction, lung edema, and hypoxemia in Ruminants

26

Which alpha-2 agonist is contraindicated in sheep?

Xylazine

27

Alpha-2 agonist GI effects

1. Decreased salivation
2. Decreased lower esophageal sphincter tone
3. Decreased GI motility
4. May induce vomiting- esp cats

28

Xylazine side effect in cattle

Uterine contractions and abortion

29

Alpha-2 agonist indications

1. Sedation of aggressive animmals
2. Sedation in the ICU
3. Sedation to manage post-op airway obstruction
3. Prevention/tx of seizures

30

Alpha-2 agonist contraindications

1. Too young or too old
2. Hemodynamic instability
3. Severely debilitated patient
4. Not suitable for most at risk patients

31

Alpha-2 agonist drugs

1. Xylazine
2. Medetomidine
3. Dexmedetomidine
4. Detomidine
5. Romifidine

32

Alpha-2 antagonist drugs

1. Atipemezole
2. Yohimbine
3. Tolazoline

33

Which alpha-2 antagonist should be used to counteract alpha-2 agonist drugs?

Atipemezole

34

Alpha-2 antagonist are always given what route?

IM

Emergency can be given IV

35

Which alpha-2 antagonist is the most specific?

Atipemezole

36

Xylazine dosages

Cattle ~10% of horses dose
Small ruminants between dog and horse dose

37

Xylazine duration

20-40min

38

Detomidine species used

Large animals

39

Detomidine route and duration

IM/IV/sublingual

90-120min

40

Romifidine species used

Horses

41

Romifidine route and duration

IM/IV

45-90min

42

Romifidine benefits

Produces less ataxia than xylazine and is preferred for standing procedures

43

Medetomidine dosing

USA- body surface
EU- body weight

Typically used in combination to reduce doses/adverse effects

44

Dexmedetomidine is ______ times as potent as medetomidine.

2x

45

Does dexmedetomidine have the same effects as medetomidine?

Yes

46

Medetomidine is a mixture of which two drugs?

Levomedetomidine and Dexmedetomidine

47

Phenothiazine drugs

Acepromazine, chlorpromazine, etc.

48

Which receptors do phenothiazines act on?

Dopamine, serotonine, alpha-1, histamine

49

Acepromazine duration

4-8 hours depending on dose

48 hours for liver patients

50

Phenothiazine CNS effects

1. Sedation (weaker than apha-2 agonists)
2. No analgesia
3. Antiemetic
4. Mild respiratory depression

51

Phenothiazine Cardiovascular effects

Vasodilation and hypotension (esp in hypovolemic animals)

Monitor bp very closely

52

Phenothiazine Other effects

1. Antihistamine
2. Antiarrhythmogenic
3. Inhibit platelet function
4. Penile prolapse in horses (not much of an issue but avoid anyway)
5. Seizures (older drugs)

53

Phenothiazine indications

1. Mild sedation for premed or post-op
2. prevention/treatment of opioid dysphoria
3. Prevention of emesis (morphine induced)
4. Sedation for dogs with laryngeal paralysis
5. Enhance xylazine in horses

54

Contraindications for phenothiazines

1. Hypovolemia or hemodynamic instability
2. Age extreme patients
3. Von-Willebrand disease
4. Boxers
5. Breeding stallions

55

Butyrophenones are very similar to which other class?

Phenothiazines

56

Butyrophenone drugs

Droperidol and azaperone

57

T/F: Butyrophenones are more likely to cause behavioral side effects.

True

58

T/F: Butyrophenones are more likely to cause the same adverse effects as phenothiazines.

False, they cause less profound of the same side effects

59

Benzodiazapine MOA

GABA receptor agonists

60

Benzodiazapine effects

Sedative, anticonvulsant, muscle relaxant

Minimal CV and respiratory effects

No analgesia

61

Benzodiazapine drugs

Agonists- diazepam, midazolam, zolazepam

Antagonists- flumazenil, sarmazenil

62

Premedication mixtures with benzos

Opioids, alpha-2 agonists or both

63

Induction mixtures with benzos

Dissociative anesthetics, barbituates, propofol

64

Diazepam characteristics

- Lipid soluble
- Formulated in propylene glycol or lipid emulsion
- low chemical compatibility

65

Diazepam administration

Slowly IV

Poor absorption and pain on IM injection

66

Diazepam duration and metabolism

Metabolized in liver

1-4 hours

67

Midazolam characteristics

-Water soluble
- Good chemical compattibiliy

68

Midazolam differences from diazepam

- More potent
- Shorter acting
- Inactive metabolites
- Can be given IM/IV or MM

69

Opioid receptors

Mu: strong analgesia, respiratory depression, dependency
Kappa: weaker analgesia
Sigma: weaker analgesia

Location: brain, spinal cord, peripheral nerves, inflamed organs

70

Opioid classifications

Full agonists: activate receptors and trigger full tissue response
Partial agonists: activate receptors but do not trigger full tissue response even at high doses
Antagonists: bind to receptors but do not activate them

Concentration dependent

71

Opioid CNS effects

1. Analgesia (acute pain)
2. Decreasing MAC of inhalants (species dependent)
3. Sedation (better with more pain)
4. Excitation, dysphoria
5. Tolerance
6. Dependence

72

Opioid vomiting mechanisms

Stimulation of chemoreceptor trigger zone outside the BBB

After entering the brain they will inhibit the vomiting center

Water soluble > lipid soluble

73

Opioid cardiovascular effects

No direct negative inotropy or vasodilation

May reduce sympathetic outflow and indirectly reduce BP

Increase parasymathetic tone to decrease HR

Suitable risk for most patients, improves Cv function be allowing reduction in anesthetic doses

74

Opioid respiratory effects

Depression of respiration not as strongly as humans/primates

Antitussive effects, may inhibit airway protective reflexes

75

Opioid GI effects

Nausea, vomiting, defecation, obstipation, spasm of the sphincter or oddi

76

Opioids other effects

Hypothermia
Post off hyperthermia
Myosis in dogs, mydriasis in cats
Inhibition of urination
Noise sensitivity

77

Opioid indications

Premedication
Perioperative analgesia
Treatment of acute and chronic pain

78

Opioid administration

ALL THE WAYS

79

Morphine

- cheap and strong analgesic
- water soluble
- Slow onset, long duration
- High individual variety in elimination
- metabolized in liver
- may case histamine release esp in high doses

80

Hydromorphone, oxymorphone

-Strong analgesics (full mu)
- duration ~4hr
- Reliable metabolism
- better choice than morphine

81

Methadone

Similar to hydromorphone

Also acts as NMDA antagonist

82

Fentanyl

-Strong analgesic (full mu agonist)
- fast onset of duration
- may accumulate after long infusions
- bolus or CRI dosages

83

Remifentanil

-Similar to fentanyl with potentcy
- Short acting and does not accumulate
-disruption of administration may trigger strong pain
- boluses may cause sudden bradycardia

84

Butorphanol

-Partial antagonist on mu and kappa (mau antagonize full mu agonists)
- weak and short acting analgesic
-may worsen pain
- used for premed w/ benzodiazepines or alpha-2 agonist

85

Buprenorphine

- partial mu agonist
- stronger analgesic than butorphanol
- long acting slow onset
- often used in cats (less excitement and easy admin)

86

Tramadol

- weak analgesic
- inhibits NE and serotonin reuptake
- not scheduled
- can be given PO

87

Opioid antagonists

Naloxone: small animals to reverse respiratory depression

Naltrexxone: long acting, antagonize wild animals after long acting opioids

88

Antibiotics

-Cefazolin
- Amoxicillin clavulic acid

Give IV 20min pre-op and every 90-120min

89

Antihistamines

Diphenhydramine: H1 antagonist

H2 antagnoist: ranitidine, famotidine, cimetitide- increase pH of stomach

Given pre-men for mast cell tumor removal