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D151 > 4- pharm LA > Flashcards

4- pharm LA Flashcards

1
Q

regional anes vs analgesia

A

regional anes - patient is still conscious, particular part of the body insensitive to pain

Analgesia- loss of pain

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2
Q

T/F LA drugs are weak bases

A

True

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3
Q

why is HCl mixed with LA drugs

A

LA drugs are weak bases and they are ineffective as base so they are mixed with HCl to form salts. these salts are water-soluble and will readily dissolve into saline solution – usuable form

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4
Q

T/F LA drugs should be hydrophobic and lipophilic

A

False!

hydrophilic - to diffuse effectively
lipophilic - to penetrate the nerve membrane (lipid bilayer)

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5
Q

T/F LA drugs act on the axon

A

False! they act on the membrane itself not on the axon

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6
Q

impulse transmission is due to ??

A

a change in polarity

INSIDE: more +

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7
Q

Properties of ideal LA solution

A
  1. reversible
  2. no irritation to tissues
  3. rapid and sufficient duration
  4. low degree of systemic toxicity
  5. should not produce allergic reaction
  6. rapidly undergoes biotransformation
  7. sterile
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8
Q

theories of LA

A
  1. ACh theory
  2. Ca displacement theory
  3. surface charge (repulsion) theory
  4. membrane expansion
  5. specific receptor
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9
Q

explain membrane expansion

A

molecules bind to the receptors of membrane –> expand –> Na channel constricted –> no ingress –> polarity does not reverse

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10
Q

Acetylcholine theory states that –

A

Acetylcholine is involved in nerve conduction, not just as a neurotransmitter in synapses

but no evidence

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11
Q

Calcium Displacement Theory

A

LA displaces calcium –> blockade of Na

Calcium ions bathing nerve does not change the LA potency

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12
Q

Surface charge (repulsion) theory

A

LA binds to surface membrane –> change EP to more + at the membrane surface –> inc threshold potential –> dec excitability

buuuuut???

  • RP is unaltered by LA
  • LA acts within membrane channel, not on surface
  • Cannot explain activity of uncharged LA e.g. Benzocaine
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13
Q

theory that can explain benzocaine’s activity

A

membrane expansion

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14
Q

T/F benzocaine has no cationic form

A

true

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15
Q

Specific Receptor

A

LA binds to specific receptors on Na channel (external or internal axoplasmic)

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16
Q

T/F amide and esters are structurally different

A

FALSE! structurally same.. both have an aromatic lipophlic group and hydrophilic end

difference: intermediate chain

17
Q

common properties of LA groups

A
  1. synthetic compound
  2. contain amino and aromatic groups
  3. weak base w/ poor water solubility
  4. combined with usually HCl to form water soluble salts
  5. alkali inc concentration of unionized free base
  6. compatible w/ epinephrine
  7. hydrolyzed by plasma cholinesterase or undergo biotransformation in the liver
18
Q

determines the relative proportion between cation (RNH+) and free base (RN)

A

pH of solution

pKa of specific compound

19
Q

when can RNH+ and RN exist in equal proportion?

A

pH = pKa

20
Q

free bases are for ____ and cations are for ____

A 
free base (RN): penetration 
cations (RNH+): nerve blockade
21
Q

T/F anes are acidic in nature

A

true

our tissues will buffer them –> cation is released

22
Q

pKa affects

A

onset

low pKa = rapid onset

23
Q

lipid solubility affects

A

potency

more lipid soluble = more potent, more toxic

24
Q

protein binding affects

A

duration

high protein binding = longer duration

25
Q

non nervous tissue diffusibility affects

A

onset

inc diffusibility = fast onset

26
Q

vasodilator activity affects

A

potency AND duration

27
Q

factors affecting the action of local anes

A

too high or too low pH
excessive dilution w/ blood/tissue fluid
too rapid absorption into general circulation
type and size of nerve to be anesthesized

28
Q

toxic reaction to LA

A

CNS

  • stimulatory phase
  • depressive phase
  • biphasic

CVS
-depressive

respiratory system
-depressive

29
Q

types of LA

A

Ester grp (benzoic acid ester, cocaine, benzocaine, PABA esters, procaine [Novocaine] , tetracaine [Pontocaine], propoxycaine [ravocaine], 2-chloroprocaine [nesacaine])

aniline derivative/non-ester

  • bupivacaine [marcaine]
  • etidocaine [duranest]
  • lidocaine [xylocaine]
  • mepivacaine
30
Q

biotransformation of ester

A

hydrolysis primarily in the plasma by plasma cholinesterase and partly in the liver

31
Q

biotransformation of amide

A

primarily in the liver by microsomal enzyme destruction and further by hydrolysis

D151 (5 decks)

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