Barbiturates Flashcards
Any drug derived from __ acid = a barb
Barbituric acid
Why have barbs fallen out of favor?
Hangover effect- residual drowsiness lasting many hours
Barbs are __ salts and are __ soluble in IV fluids
Sodium salts
Highly soluble
Because they are highly alkaline, they easily __ with opioids, catecholamines, and NMB
Precipitate
Barbs are only available as a __ % solution due to caustic to vessels
2.5%
Substitutions at 2 and 5 carbons gives different effects.
Sulfur at 2 and 5-
Sulfur at 2 and 5- increase lipid solubility
Substitutions at 2 and 5 carbons gives different effects.
Phenyl at 2 and 5-
Anti-convulsant
Substitutions at 2 and 5 carbons gives different effects.
Methyl group at 2 and 5-
Convulsive activity
Prompt awakening from barbs is due to
Redistribution
Test question
What ion is associated with GABA receptors?
Chloride
Test question
Barbs have a unique ability to depress BOTH __ and __
Reticular activating system
SNS ganglia- leading to hypotension
Non ionized fraction exerts pharm effect
Test question
Patients on highly protein bound meds such as __ and __ increase barb effects
ASA
phenytoin
Patients with cirrhosis and neonates have __ sensitivity to barbs
Greater
Maximum brain uptake in __ seconds for thiopental and methohexital
30
Initial decreases in plasma concentrations of barbs are due to redistribution to __
Skeletal muscle
Barb levels continue to rise in __ 30 minutes post injection
Fat
Calculate induction drugs using __ body weight
Lean
Acidosis __ barb effects
Increases
Alkalosis __ barb effects
Decreases
Due to alterations in the non-ionized fractions
Cardiopulmonary bypass __ systemic clearance of barbs
Decreases
Oxi-barbiturates are metabolized __
Hepatic only
Thio-barbs (with the sulfur) metabolize
Mainly hepatic but also kidneys and CNS
Barb metabolism is __.
Slow
Enzyme induction may __ the dose requirements but does not modify the duration of action.
Increase
Do roach of the liver patients have any difference in barb clearance?
No
Methohexital hepatic clearance is __x greater than thiopental, therefore it has the least hangover
4x
While redistribution determines awakening, __ determines complete recovery.
Metabolism
Old age __ anesthetic effects of barbs
Increases
Peds patients recover __ due to more rapid hepatic clearance
Quicker
Barbs are cerebral vaso__
Constrictors
Barbs __ provide sedation in the presence of pain, they actually can lower the pain threshold.
Cannot
Barbs have __ skeletal muscle relaxation
No
Methohexital has __ risk of excitatory phenomena like hiccups and myoclonus, which are dose related.
Increased
Thiopental induction dose
3-5 mg/kg
This is how I remember it, since it clears 4x slower than metho, give 4 mg/kg
Methohexital induction dose
1-1.5 mg/kg
Same as succs
Lower BP with barbs due to peripheral __ due to depressed medullary vasomotor centers, decreased SNS outflow
Peripheral vasodilation
Hypovolemic patients are extremely vulnerable to marked decreases in BP from barbs, so __
Don’t use barbs with hypovolemic peeps
Barbs- give ‘em __
Quick
Barbs depress ventilation and __ sensitivity to high CO2, but do not depress laryngeal or cough reflexes
Decrease
Barbs an evoked potentials?
No interference
Barbs __ enzymes to a max of doubling metabolism rates
Induce
Barb-related enzyme induction results in increased metabolism of other drugs like __
Coumadin Phenytoin Tricyclics Corticosteroids Vit K
Barbs are contraindicated with __ patients due to stimulation of heme production
Porphyria
Should you give barbs intra-arterial?
No
Immediate vasoconstriction and excruciating pain, gangrene, precipitation of crystals leading to arteritis.
What barb induces enzymes the most?
Phenobarbital
Venous thrombosis after barb admin due to __
Deposition of barb crystals
Barb thera index __ with tolerance.
Decreases
Allergic reaction to Thio around 1:__,000 , seen more often with prior Thio exposure or chronic atopy, meaning IgE hypersensitivity such as __
1:30,000
Hay fever Asthma Infantile eczema Urticaria Food reactions
Thio mixtures are highly __
Bactericidal
