Barbiturates Class (Dr. E's lecture) Flashcards Preview

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1

How are barbs commercially prepared?

as sodium salts

2

How are barbs prepared with respect to pH? why?

HIGHLY Alkaline formulary (about pH >10)
they're unstable

3

At room temp, what is different about TPL?

prepared TPL is stable and sterile for at least 6 days

4

What types of isomers are in the Barbs?

Racemic Prep, BUT levo isomer is the potent one

5

What are barbiturates derived from? what constitutes this?

Barbituric Acid
Urea + Malonic Acid = Barbituric Acid

6

What makes a barbiturate, chemically speaking with regards to structure? What effects does this cause?

Substitutions at Carbon 2 and 5; have sedative, hypnotic properties

7

What does it mean if there is a branched chain at C # 5 for the structure of Barbs?

-Branched Chain at #5 increases hypnotic activity

8

If there is an Oxygen at Carbon #2 what does this mean?

OXYbarbiturate (Phenobarbital, Pentobarbital, Methohexital)

9

If there is a Sulfur at Carbon #2 what does this mean?

THIObarbiturate (Thiopental)

10

What does it mean if there is a phenyl group at C # 5 for the structure of Barbs?

-Phenyl group at #5 increases ANTIconvulsant activity (phenobarbitol)

11

What does it mean if there is a methyl radical imparted in the structure of Barbiturates?

-Methyl radical imparts CONVULSANT activity (methohexital)

12

What does it mean if there is sulfuration in the structure of barbs?

-Sulfuration=fat soliuble, as lipid solubility increases: shorter duration, more rapid onset, increased potency

13

What is different regarding the long vs straight chain w/r/t the structure/activity relnships of Barbs?

-long branched chain is more potent than a straight chain

14

What are the relative potencies of TPL, Thiamylal, and Methohexital?

TPL: 1
Thiamylal: 1.1
Methohexital: 2.5

15

What is the MOA of Barbiturates?

-decreases the rate at which GABA dissociates from its receptor->increases duration of GABA activated Cl channel opening (enhances GABA)
-Mimics GABA at the receptor
-Decreases POST-synaptic membrane sensitivity to Ach-> some muscle relaxation- NOT surgical depth
-Also Directly decreases the transmission in the sympathetic ganglia-->hypotension
-interaction with GABA receptor produces functional inhibition of the postsynaptic neuron

16

What does Barbs mimic physiologically?

Depresses RAS-> SLEEP

17

What is the onset of barbs?

RAPID onset of action

18

What is important about the redistribution of Barbs?

Redistribution=Rapid termination of Effect

19

Is TPL protein bound?

70-85% protein bound

20

What is the fat: blood partition coefficient? what does this mean?

11= veryyyyy lipid soluble

21

what should you calculate your dosage of barbs based on?

IBW

22

If the patient is alkalotic, what does this do to the barbs?

alkalosis decreases the intensity of Barbs

23

If the patient is acidotic, what does this do to the barbs?

intensifies effect

24

Are barbs acids or bases?

WEAK acids!!!!! remember they are ACIDS, although they are prepared in >10 pH alkaline soln

25

How are oxybarbiturates metabolized?

Hepatic ONLY

26

How are thiobarbiturates metabolized?

Hepatic and some extra hepatic

27

What terminates pharmacologic activity?

side chain oxidation at C#5 to Carboxylic Acid

28

Generally, how are the barbs metabolized?

desulfuration, hydrolysis, opens ring to water soluble combounds

29

How are barbs excreted?

renal primarily; < 1% excreted unchanged

30

Do barbs have active metabolites?

NO active metabolites