Week 2 Weak Acids & Bases & pKa (Everything) Flashcards
1
Q
LA are:
A
weak bases
2
Q
Acid + Acid =
Base + Base =
A
non ionized
3
Q
Acid + base =
A
ionized
4
Q
Onset of LA
pH where 50% ionized and 50% non-ionized
A
pKa
5
Q
Lipid solubility:
A
potency of LA
6
Q
the more lipid soluble:
A
the more potent.
7
Q
More lipid soluble impact on blood flow…
A
less likely for blood flow to carry it away
8
Q
Protein binding=
A
duration of LA
9
Q
Na+ channel are voltage gated and exist in
A
3 phases
10
Q
The 3 phases of Na+ channel voltage gates:
A
- Resting or closed (M-gate closed)
- Activated or open (M-gate and H-gate are open)
- Inactivated (inactivated b/c H-gate is closed)
11
Q
the LA interacts with the ______ to cause the effect
A
the H-gate
12
Q
is a positive or negative charge of the LA required for the interaction with the H-gate to happen?
A
positive charge
13
Q
what is the position of the M-gates and the H-gate when the na-channel is RESTING:
A
M-gates: closed
H-gate: open
14
Q
what is the position of the M-gates and the H-gate when the na-channel is ACTIVATED:
A
M-gates: open
H-gate: open
15
Q
what is the position of the M-gates and the H-gate when the na-channel is INACTIVATED:
A
M-gates: open
H-gate: closed
16
Q
M-gates: open
H-gate: closed
the na-channel is:
A
inactivated
17
Q
M-gates: open
H-gate: open
The na-channel is:
A
Activated
18
Q
M-gates: closed
H-gate: open
The na-channel is:
A
Resting
19
Q
Recover from the inactivated, refractory state requires closure of the _____ and opening of the _____.
A
closure of the m-gates
and opening of the h-gate.
20
Q
LA bind to the (R) where?
A
within the channel
21
Q
How do LA access the Receptor?
A
via the membrane phase OR from the cytoplasm
22
Q
What form of the LA is needed to cross the phospholipid layer?
A
non-ionized
23
Q
What for of the LA is needed to get inside the membrane in order to bind w/the H-gate?
A
ionized
24
Q
Lipid soluble (non/ionized?)
A
non Ionized
25
Uncharged form ((non/ionized?)
non Ionized
26
Acid form (non/ionized?)
non Ionized
27
Generally hydrophobic (non/ionized?)
non Ionized
28
Readily penetrates BBB and Placenta (non/ionized?)
non Ionized
29
Water soluble (non/ionized?)
ionized
30
Charged Form (non/ionized?)
ionized
31
Conjugate base form (non/ionized?)
ionized
32
What delays onset?
- drug with pKa farther from physiological pH (7.4). In this state more of the drug exists in the ionized form
- environmental pH is acidic (<7.4);
33
examples of environments where pH is more acidic (<7.4):
- wound infections
| - ischemic areas
34
examples of environments where pH is more acidic (<7.4):
- wound infections
| - ischemic areas
35
Highly protein bound = what 2 things?
1. harder to dissociate from Na channel
| 2. Longer DOA
36
DOA is associated with
Protein binding!
| -higher protein binding = longer DOA
37
The closer pKa is to physiologic pH the faster the
onset (relatively)
38
to speed up onset:
pKa closer to physiologic pH
39
pKa of Chloroprocaine:
9.1
40
protein binding of Chloroprocaine:
none (Zero)
41
pKa of Procaine:
9.1
42
protein binding of Procaine:
None
43
Drug that's the Exception to the rule of faster onset
Chloroprocaine
44
pKa of Lidocaine
7.6-7.9
45
what can be used/added to the LA to either prolong the duration?
EPINEPHRINE
46
What can be used/added to LA to gain quicker onset:
Bicarbonate
47
What LA can precipitate when adding bicarbonate?
Bupivacaine
48
**What is the dose of bicarbonate when mixed with Bupivacaine?
0.1 mEq per 20mL of Bupivacaine
49
**What is the dose of bicarbonate when mixed with Lidocaine?
1 mEq of Bicarb per 10mL of Lidocaine
50
***Epi will not increase DOA for
| Why?
Bupivacaine
Etiocaine
Ropivacaine
-b/c they have a long duration naturally
51
Which LA are short acting?
"Pro-C"
Procaine
Chloroprocaine
52
Which LA are intermediate acting?
"LMP"
Lidocaine
Mepivacaine
Prilocaine
53
Which LA are long acting?
"BET on a LONG shot"
Bupivacaine
Etidocaine
Tetracaine
54
Prilocaine Short/Intermediate/Long acting LA?
short
55
Lidocaine Short/Intermediate/Long acting LA?
Intermediate
56
Bupivacaine Short/Intermediate/Long acting LA?
Long
57
Tetracaine Short/Intermediate/Long acting LA?
Long
58
Chloroprocaine Short/Intermediate/Long acting LA?
short
59
Etidocaine Short/Intermediate/Long acting LA?
long
60
Mepivacaine Short/Intermediate/Long acting LA?
intermediate
61
```
Drug X (a weak acid) has a pKa of 8.4 and is administered to a patient with a pH 7.4. Which of the following is true regarding the drug?
A) more than 50% ionized
```
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
B: more than 50% unionized
62
```
Drug X (a weak acid) has a pKa of 3.5 and is administered to a patient with a pH 7.4. Which of the following is true regarding the drug?
A) more than 50% ionized
```
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
A: more than 50% ionized
63
```
Drug X (a weak acid) has a pKa of 3.5. Which of the following is true regarding the drug?
A) more than 50% ionized
```
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
D): cannot be determined with information provided
64
```
Drug X (a weak base) has a pKa of 3.5 and is administered to a patient with a pH 7.4. Which of the following is true regarding the drug?
A) more than 50% ionized
```
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
B) more than 50% unionized
65
```
Drug X (a weak base) has a pKa of 9.5 and is administered to a patient with a pH 7.4. Which of the following is true regarding the drug?
A) more than 50% ionized
```
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
A) more than 50% ionized
66
Lidocaine has a pKa of 7.7 and is administered to a patient with a pH 7.7. Which of the following is true regarding the drug?
A) more than 50% ionized
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
C) 50% unionized and 50% ionized
67
Weak bases become more ________ as pH increases
Non-ionized
68
Should a weak acid be stored in a low or high pH solution? Why?
High pH solution (base)
Base + Acid = Ionized form
Should not precipitate
Mixing a weak acid with low pH solution would cause precipitation
69
When a local anesthetic is injected into a physiologic pH environment, it will be:
A) less than 50% ionized
B) less than 50% unionized
C) 50% unionized and 50% ionized
D) Cannot be determined with information provided
B: less than 50% unionized (LA are weak bases)
70
pKa range for LA
7.6-9.1
71
how would an area of infection alter a LA block
Speed of onset is slower when LA is injected into an area of infection b/c it increases the extent of ionization which slows diffusion through the lipid bilayer
72
what creates a faster onset for LAs
more unionized form = faster the onset
| bc unionized is what crosses the membrane then it is activated to ionized form
73
which LA are short acting
"Pro-C"
| procaine & chloroprocaine
74
which LA are intermediate acting
"L,M,Pri"
| Lidocaine, Mepivicaine, Prilocaine
75
which LA are long acting
"BET on a long shot"
bupivicaine, etidocaine & tetracaine
(not appropriate for outpatient surgery centers where we need to move the patients quickly. tetracaine last around 4 hours)
76
LA with high a pKa are ____ at physiologic pH?
| and require what fore effect?
Are highly ionized at physiologic pH
Has to have an open (activated) Na+ channels for effect
77
which nerves have more frequent depolarization and what LA pKa are they susceptible to?
sensory & autonomic nerves
| susceptible to high pKa LA
78
which nerves have less frequent depolarization and what LA pKa are they susceptible to?
motor nerves
| susceptible to lower pKa LA
79
where is a sympathetic block compared to a sensory block
Sympathetic block is 2-6 dermatomes higher than sensory block
80
where is a motor block compared to a sensory block
Motor block is 2 dermatomes lower than sensory block
81
How does the LA progress in a blockade?
* Autonomic, Temperature, Pain (ATP)
* Touch, Pressure (TP)
* Motor, Vibratory, Proprioception (MVP)
82
what form of a drug can diffuse across the lipid bilayer into the axon in a conduction block?
Non-ionized
83
what is the role of the ionized form of a LA in a conduction block
Ionized is needed to attach to the inside of the sodium channel and lock it in the inactivate state
84
conduction blocks are _____ dependent?
frequency dependent
| frequency of the Action Potential
85
special consideration about myelinated axons. what must happen to achieve a block
2-3 nodes of Ranvier must be blocked to stop nerve conduction myelinated axons
86
WEAK ACIDS COMBINE WITH POSITIVE CHARGED IONS SUCH AS:
Na+
Mg++
Ca++
87
WEAK BASES COMBINE WITH NEGATIVELY CHARGED IONS SUCH AS:
CHLORIDE
| SULFATE
88
Example: are the following "drugs" weak acids or weak bases?
LIDOCAINE HYDROCHLORIDE:
SODIUM CETO:
MAGNESIUM TIBUCAINE:
LIDOCAINE HYDROCHLORIDE: weak base
SODIUM CETO: weak acid
MAGNESIUM TIBUCAINE: weak acid
89
example question:
Drug X (a weak acid) has a pKa of 8.5 and is administered to a patient with a pH 7.4. Which of the following is true regarding the drug?
A) more than 50% ionized
B) more than 50% unionized
C) 50% unionized and 50% ionized
D) cannot be determined with information provided
B: more than 50% unionized
