Flashcards in Weak Acids and Weak Bases Deck (34):
Weak Acids become more ________ as pH falls (H+ increases)
Acid + Acid = ?
The pKa of a Weak Acid is the pH at which ___% of the Weak Acid is in ionized form and ___% is NONionized
Ex. the pKa of Thoipental is 7.6; if the pH is 7.6 50% of the thiopental is Ionized and 50% of the thiopental is NONionized
The pKa is _______ for different weak acids;
- one weak acid may have a low pKa of 2.3 while another may have a high pKa of 11.2.
- A given weak acid may have any pKa.
- The pKa is constant for a given weak acid
______ drug penetrates the BBB and the placenta barrier; the more _________ the drug, the greater the transfer to the brain or fetus.
strictly speaking the NONionized for of the weak acid is the acid, and the ionized form is called the ______ ____
the greater the pKa of a weak acid, the _____ the amount of drug in NONionized form at physiologic pH (7.4)
Will induction w/ thiopental be faster if the pt is acidotic or alkalotic? explain!!
- when the pt is acidotic more of the injected thiopental will be NONionized (acid + Acid = NONionized). Thiopental will diffuse in greater amounts across the BBB b/c more of the drug is in the NONionized form. NONionized drugs readily penetrates the BBB
Should you mix thiopental w/ a low pH solution? why or why not?
- When thiopental is mixed w/ a solution of low pH ( pH 3.0, for example) most the thiopental will become NONionized (acid + acid = NONionized).
-The NONionized drug, b/c it is poorly water soluble, tends to precipitate.
- Rule: Mixing a weak acid w/ a low pH solution may lead to the formation of precipitate
Why is thiopental stored in a solution w/ a pH = 10-11?
-When thiopental is stored in a solution w/ a pH of 10-11, most of the thiopental is in the ionized form. the Ionized form is highly water soluble. A precipitate will not form when the thiopental is stored in a solution w/ a high pH
Weak Bases become more _______ as pH increases (H+ decreases)?
base + Base = NONionized
The pKa of a weak base is the pH at which ____% of the weak base is in the ionized form and ___% of the weak base is in the NONionized from.
- Ex. The pKa of Lidocaine is 7.7, if the pH is 7.7, 50% of the Lidocaine would be in the ionized form and 50% of the lidocaine will be in the NONionized form
-When lidocaine is injected into the body w/ a pH of 7.4 less than 50% (24% in this case) will be NONionized
base + acid = Ionized
The pKa is ______ for different weak bases; one may have a low pKa of 2.6 while another may have a pKa of 9.8.
- A given weak base may have any pKa
- The pKa however is constant for a given weak base
Numerous drugs in anesthesia are Weak Bases name 4!
Strictly speaking, the NONionized form of a weak base is the base, and the Ionized form is called the ___ ____
Another way to say that a substance has accepted a hydrogen ion is to say the substance is what?
the pKa of LA's range from 7.6-9.1. which LA will be most NONionized at a pH of 7.4. the one with a pKa of 7.6 or the one with a pKa of 9.1? explain your answer.
- Mepivacaine (pKa 7.6) is 39% NONionized at a pH of 7.4
- Chloroprocaine (pKa 9.1 ) is 2% NONionized at a pH of 7.4
What combination will most facilitate trapping of LA by the fetus?
A) Maternal ALKalosis and Fetal ALKalosis
B) Maternal ALKalosis and Fetal ACIDosis
c) Maternal ACIDlosis and Fetal ALKalosis
D) Maternal ACIDalosis and Fetal ACIDosis
B) Maternal ALKalosis and Fetal ACIDosis
What condition most prevents passage of LA from fetus to mom?
A) Maternal ALKAlosis
B) Maternal ACIDosis
C) Fetal ALKAlosis
D) Fetal ACIDosis
D) Fetal Acidosis
The speed of onset of a LA is related to what?
The_____ the pKa of a LA, the greater the proportion of LA in the NONionized for at a pH of 7.4; and the faster the ONSET if the conduction block
What determinant of a LA determines the potency?
In general the _____ lipid soluble the LA the greater it's potency
What single change in a property of a LA will result in a more potent and longer acting agent?
An increase in lipid solubility
- An increase is lipid solubility will increase the duration of the block and the potency
what 2 factors are related to the Duration of action of a LA?
Protein binding and lipid solubility
the duration of action is greatest for LA's that exhibit the greatest ___ ____ and the highest ____ _____.
- Lipid Solubilty
______ However is more important than ____ she it comes to duration of action
- Protein Binding
- Lipid Solubility
rank the tissues from highest to lowest for LA absorption
- Brachial Plexus
- SA, Sciatic, Femoral
I Think I Can Push Each Bolus SSlowly For Safety
For militated axons __-__ nodes of Raniver must be blocked to stop nerve conduction
Conduction block is _____ dependent
- the Greater the frequency of the action potentials, the faster the nerve is blocked by LA's
- The LA must attach to the Na+ channel when it is in the inactive star, the faster the nerve is firing, the more opportunities the LA will have to "catch" the Na+ Channel in the inactive state
Both NONionized and Ionized form of the LA are required for a ______ block?
- the NONionized form diffuses across the lipid by layer into the axon, and the ionized form attaches to the inside Na+ channel and locks it into the inactive state
___ ___ Na+ channels are found only in the nerve's Axon
what is the order in which toxic manifestations to LA occur?
-lightheadedness, tinnitus, visual disturbances, numbness of tongue, muscle twitching
- Unconsciousness, Coma, Respiratory Arrest
- Cardiovascular depression