Premedication Flashcards
MOA for Anticholinergics
competitive antagonist for muscarinic receptor
Anticholinergics effects
o CV- mainly tachycardia o Lung- bronchodilation, reduces secretions & increases viscosity o Eye- Mydriasis +/- increase IOP o GI- decreased motility o CNS- sedation/ hallucination ( humans)
What are two examples of anticholinergics?
Atropine and glycopyrrolate ( does not pass BBB or placenta)
Metabolism differences with atropine
spp. dependent
• Dog & human- hydrolysis & excreted unchanged
• Cat & small ruminant- hepatic & renal esterase
• Rabbits have atropinase; so better to use glycopyrrolate
Should anticholinergic be used as a premed?
No longer routinely used as premed, BUT should be used without hesitation to treat bradyarrhythmia & hypotension
Phenothiazine MOA
D2, a1, H1 & muscarinic antagonist
Phenothiazine Effects
o CV- potent vasodilation +/- antiarrhythmic
o GI- antiemetic, delay gastric emptying
o CNS- tranquilization (+ opioid= neuroleptoanalgesia), decreased MAC
Less reliable than a2 agonist
o Hematologic: decreased hematocrit via vasodilation & decreased plt aggregation
o Antihistaminic
o Temperature: hypothermia
Should I give acepromazine to a Boxer?
NO- can cause vasovagal syncope or CV collapse!
Can acepromazine be reversed?
NO, it last 12 hours and relies on hepatic metabolism
When should you not use acepromazine?
DO NOT use in pediatric, geriatric, debilitated & pt. with hepatic dysfunction
• Poor choice for aggressive or excitable patients because less reliable than a2 agonist!
Acepromazine side effects
- Pro: good anti-emetic
* Con: vasodilation causing reduced BP, priapism, CV collapse in boxer (vasovagal syncope)
Benzodiazepine MOA
allosteric modulator of GABA at GABA A receptor
NO DIRECT ACTION
Benzodiazepine effects
sedation, anxiolytic, anticonvulsant & muscle relaxant
+/- excitement in healthy cat or dogs
When should you use benzodiazepine as a sedative?
very young, very old, very sick, small ruminant and pigs
CV & respiratory effect of benzodiazepine?
minimal
Telazol spp. difference in metabolism:
Cat & Pig: Tiletamine > Zolazepam allowing for a smooth recovery
Dogs & Horses: Zolazepam > Tiletamine resulting in a rough recovery
What is a competitive antagonist for benzodiazepines?
Flumazenil
Why are ruminants more sensitive to a2 agonist?
Because have a2D receptor ( unique to ruminants)
a2 agonist effects
CNS- sedation (caution touch & sound sensitive) & analgesia
GI- vomit & decreased motility
CV- Biphasic & reduces CO!
• P1- increased BP & decreased HR
• P2- decreased BP & decreased HR
Thermoregulation- decreased
Respiratory: mild, cyanosis (turn grey), small ruminants can get pulmonary edema
M/S: muscle relaxant
Uterus: ecbolic effect (induce contraction)
Renal: increased urine production
Endocrine: hyperkalemia ( large cat) & endogenous insulin suppression causing hyperglycemia
IOP & ICP: do not use rx if high, does not change but vomiting can increase!
Should you give an a2 agonist to a neonate?
NO! They rely on HR to maintain CO!
Why give a2 agonist?
Reliable (most recumbent, but horse will stay on feet), can be reversed, has analgesic effect and can be administered via a lot of routes.
What are three a2 adrenergic antagonist?
- Tolazoline
- Yohimbine
- Atipamezole
What route should Atipamezole be given?
IM ONLY! IV is associated with sudden death
