Drugs Flashcards
Drug classes used to premed
anticholinergics phenothiazines alpha 2's benzodiazepines opioids
Anticholinergics used for pre-med
Atropine
Glycopyrrolate
Atropine
- can cross BBB, placenta b/c liphophyllic
- shorter onset & duration = drug of choice for emergency bradycardia
Glycopyrrolate
- longer onset & duration
Contraindications for anticholinergics
- causes ileus in EQ
- not useful in rabbits, rum b/c atropinase & rumen microflora eliminates drug too fast (use glyco instead)
- don’t used concurrently w/ alpha 2’s
How do anticholinergics work?
block ACH at muscarinic receptors –> anti SLUDGE (block parasymp activity)
Effects of anticholinergics
Increase HR
Bronchodilation
Decrease secretions, GI activity
Phenothiazines used for pre-med
Acepromazine (IV, IM, SQ)
Trazodone (PO)
Acepromazine
- dilute and non-dilute forms - calculations/doses vary
- potent venodilator
How do phenothiazines work?
alpha 1 antagonist - block excitatory NT’s (dopamine & NE) to tranquillize
Reduces anxiety w/o causing excessive sedation
no reversal
Contraindications for phenothiazines
- avoid in shocky patients (d/t vasodilation, hypotension)
- caution in seizure patients, may increase incidence
- weak anti-histamine - may cause reflux (relaxes gastric sphincters) or impact skin allergy tests
- paraphimosis in breeding stallions
Effects of phenothiazines
- Tranquilization lasting 3-6 hrs (visible 3rd eyelid)
- Bradycardia, hypotension/vasodilation
- Decreased RR
- NO analgesia
What are phenothiazines used for clinically
- calm active/anxious patients
- treat hypertension
- antiarrhythmic for catecholamine-induced arrhythmia (NOT trauma-induced)
Alpha 2 agonists used for premed
- Xylazine
- Romifidine
- Detomidine
- Medetomidine
- Dexmedetomidine
How do alpha-2 agonists work?
- affect descending inhibitory pathway to cause analgesia
Contraindications for alpha 2’s
- don’t pre-treat with anticholinergics
- if concerned about arrhythima
Effects of alpha 2’s
- sedation (CNS depression)
- excellent analgesia
- vasoconstriction/hypertension –> hypotension (prolonged in EQ), bradycardia (may see cyanosis - give O2)
- hyperglycemia (anti-insulin effect)
- diuresis (anti-ADH effect on kidney)
- decreased RR, stridor
- GI stasis
What are alpha 2’s used for clinically?
- recommended only to use in younger, healthy patients (b/c resp and CV complications)
- outpatient sedation
- causes emesis in cats
- epidural in EQ/cattle
List alpha 2’s from least to most potent
Xylazine < Romif < Detom < Mede < Dexmed
Xylazine least potent, needs greater dose/bigger volume
What drug class causes phantom kicks in EQ & random arousal in SA
Alpha 2’s (more specifically Xylazine?)
Why don’t you want to use an anticholinergic to pretreat for the bradycardia seen w/ alpha 2’s?
Anticholinergic will increase work of heart, but no benefit to CO b/c periphery still vasoconstricted
Can use once in bradycardia/hypotension stage tho
Common drug protocol to sedate a fractious patient? SA vs. LA?
SA - Alpha 2 + opioid or Ace (reduce random arousal)
LA - Detomadine + Torb or Ace to decrease phantom kicks, but also low vol so can give quicker w/ pole syringe
What drug class should you not give to sheep? Why?
alpha 2’s/xylazine - damage lung tissue, cause hypoxia, pulmonary hemorrhage
Benzo’s used for premed
Midazolam
Diazepam
(Zolazepam)
How do benzo’s work?
- modulate GABA release to increase CNS inhibition
- no analgesia
Contraindications for benzo’s
- may cause abberant/dissociative behavior in young healthy SA/EQ
- can cross placenta –> neonate depression
- don’t give repeated PO dose to cats in liver failure - worsens it
Effects of benzo’s
- reduce muscle hypertonicity (esp. EQ)
- stops seizures
- appetite stim in cats
- may increase anxiety/excitement
- Yay minimal CV and Resp effects
What are benzo’s used for clinically?
- sedation
- seizure treatment
- appetite stim in cats
Reversals for Benzo’s
Flumazenil (but $$)
Reversal for opioids
Naloxone (short acting)
Naltrexone (longer acting)
Effects of opiods
- analgesia, some sedation
- bradycardia
+/- vomiting (morphine, hydro, torb) - resp depression
- dysphoria, excitement
How could you counter the histamine release caused by morphine?
Acepromazine is an antihistamine
morphine
histamine release
excitement in cats
methadone
helps w/ windup
decreases chances of vomiting
only opioid used for sedation
Butorphanol (torb)
