Pharm II, Inj. Anesthetics
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Pharm II, Inj. Anesthetics
Pharm II, Inj Anesthetics
The effect site for injectable anesthesia?
Rout of admin for wildlife/zoo animals, usually suboptimal?
Route of admin for very small animals?
Relative to IV, drawbacks of using IM for anasthetics (6):
Higher dose required
No secure Venous Access
Must use small volume
Must be non-irritant
What factors affect the seed of onset (5)?
Rate of admin
What drug properties affect the speed of onset (4)?
What P factors affect the speed of onset?
Plasma Protein Concentration
What influence does lipid solubility have on drug?*
+lipid solubility-> crosses membranes faster
What influence does molecular weight have on drug?
Smaller MW -> Cross BB faster
What influence does Protein binding have on drug?*
Determines how much drug can leave vascular space and exert effects (hypoalbuminaemia= greater Fx)
What influence does Ionization have on drug?*
Ionized drugs cannot cross membrane
(pH changes can cause ionization of drug)
What factors influence Distribution?
After Admin, plasma concentrations fall b/c of... (3)
Redistribution (to vessel rich tissues, muscle, fats)
Elimination (through metab and excretion)
What factors affect recovery?
Duration of admin
Distribution to other tissues
Elimination 1/2 Life
How are barbiturates categorized?
What is Thiopental classified as?
Thiopental, not in solution, is classified as..... (pH)
Weak Organic Acid
Thiopental, IN solution, is classified as ... (pH)
10.5, HIGHLY ALKALI
Once injected, what happens to Thiopental?
The pH falls (blood is 7.4) and becomes UN-IONIZED
One reconstituted, what is the shelf life of Thiopental?
7 Days (High pH = bactericidal)
Thiopental concentrations greater than ____%, can cause sloughing, pain and self trauma
(Dilute w/ SQ ++NaCl if accidental peri-vascular injection)
Thiopental Mechanisms of Action (3):
Interacts with GABA to increase the duration of GABAa dependent Cl channel in the CNS= Hyperpolarzation and Neurolnal Inhibition
Depresses the reticular activating system in the brainstem => sleepy
Depresses transmission in sympathetic ganglia
Speed of onset:
Speed of Redistribution:
: VERY rapid (<30 sec)
What increases the effects of barbiturates?
Hypoproteinaemia (active form unbound)
Ionized VS Unionize
Which is in plasma?
Which is Active?
Both are in plasma
Un-ionized is active (highly lipid soluble, crosses BB)
What technique can increase the rate of induction and recovery?
Rapid Inj using Minimal Effective Dose
Why isnt thiopental used for maintenance?
It is cumulative
Two determinants of thiopental induction dose requirements:
Lean Body Mass
Avoid Thiopental in...
Thin Animals (little depot)
Use caution in hypovolemia/shock/cardio Dz
Thiopental CNS Fx (3):
Rapidly Crosses BBB
Thiopental Cardio Fx (4):
Thiopental Respiratory Fx:
Advantages of Thiopental (2):
Potent & Short Acting
Long history of use in many species
Disadvantages of Thiopental (7):
CVS and Resp Depression
Fx depend of admin technique
Solutions dont mix with other drugs
Barbiturate used for ET:
Pentobarbital +/- Phenytoin
Propofol is classified as a...
Lipid Solubility of Propofol:
HIGHLY lipid Soluble
Protein Binding of Propofol
High Protein Binding
Shelf life of Propofol:
12-24 hrs, in fridge
Propofol is available as...
1% or 2% emulsion in
10% soybean oil
1.25 purified egg phosphatide
pH of Propofol
Propoclear is a _____ formulation of propofol
: Exceeds Hepatic Flow
: Rapid (except in cats) & No hangover
Propoclear should be administered____
Proprclear CNS Fx (4):
Anti-convulsant (give w/ Propofol)
Propoclear Cardiovascular Fx(4):
Inhibit/Reset Baroreceptor Reflex
Propoclear Respiratory Fx(2):
Important Propoclear Side Fx(4):
Pain on Injection
Administration of Propofol slowly => (2)
Min Respiratory Depression
Tx for persistant Propofol Shakes
Which is used for epileptic dogs that don't respond to Valium?
Cats should not anesthetized on consecutive days with...