Lecture 16 (Exam 4) - Local Anesthetics Pt. 1 Flashcards
Procaine
- Amide or Ester?
- Metabolite?
- How is this excreted?
- Why do we like this drug a lot?
- Ester (only 1 “i”)
- PABA (ParaAminoBenzoic Acid)
- Excreted via urine - UNCHANGED!
- Ester hydrolysis metabolism = fast! & it is very short acting 😁
Slide 34
What LA is shorter acting than Procaine?
It is ____x as fast.
How must it be metabolized?
Chloroprocaine!
3.5x faster!
Metabolized by Plasma Cholinesterases, too!
*Castillo put a Podcast (not tested) on BB
Slide 34
🤰 Does pregnancy ↓ or ↑ plasma cholinesterase?
By what %?
Decrease by 40%.
- pay mind to your drugs metabolized this way.
Slide 34
Tetracaine
Do we use this a lot?
What is the order of metabolism (fastest to slowest) for these LA: tetracaine, chloroprocaine, procaine.
No!
Chloroprocaine > procaine > tetracaine
Slide 34
With dose-dependant effects of Lidocaine intravascularly, what plasma concentration (dose) do we give to have an analgesic effect?
1-5 mcg/ml
(slide 7)
With dose-dependant effects of Lidocaine intravascularly, what plasma concentration (dose) causes the effects of:
Circum-oral numbness
Tinnitus
Skeletal muscle twitching
Systemic hypotension
Myocardial depression
5-10mcg/ml
(slide 7)
Which LA is the only weak acid?
What’s the pKa?
Benzocaine, pKa 3.5
*we usually spray this in anesthesia- but Orajel is the 🐐 when you have a canker sore.
Slide 35
With dose-dependant effects of Lidocaine intravascularly, what plasma concentration (dose) causes the effects of:
Seizures
Unconsciousness
10-15mcg/ml
(slide 7)
List some of the reasons we would use Benzocaine.
What is the onset?
DOA?
Dose?
Intubation w/ reactive airway disease, Endoscopy, TEE (transesophageal echocardiography), bronchoscopy
Onset: RAPID 💨
DOA: 30-60 mins
Dose: One 1 sec spray (20%) = 200 - 300 mg
Slide 35
With dose-dependant effects of Lidocaine intravascularly, what plasma concentration (dose) causes the effects of:
Apnea
Coma
15-25mcg/ml
(slide 7)
You suck at intubating bc you are a baby SRNA so you decide to spray extra doses of Benzocaine.
Is this okay?
No - you can cause Methemoglobinemia and your pt will become a Smurf. (might die)
Slide 35
With dose-dependant effects of Lidocaine intravascularly, what plasma concentration (dose) causes the effects of Cardiovascular depression (RIP)
> 25mcg/ml
(slide 7)
With LA, what is the molecular structure made of? (3 parts)
- Lipophilic portion (first)
- hydrocarbon chain (middle)
- hydrophilic portion (end)
(slide 8)
The bond between which 2 parts of the LA molecular structure classifies it as either an Ester or Amide?
- Lipophilic portion (first)
- hydrocarbon chain (middle)
(slide 8)
For LA molecular structure and its 3 parts, what are the names and associations to the Aromatic Benzene Ring?
- Lipophilic portion (first) - Aromatic Part
- hydrocarbon chain (middle)- Intermediate chain
- hydrophilic portion (end) - Amino group
(slide 9)
Please for the love of Schmidt you better know how to convert pounds to Kg’s…
Answer: 436.5 mg
*remember MAX dose of Methylene Blue is 8 mg/kg
Slide 36
How can we differentiate between an ester vs amide when looking at drug names?
amides have 2 i’s in its name
esters have 1 i in its name
(slide 9)
In regards to the aromatic benzene ring, What 2 parts differentiates the linkage between being an amide vs ester LA?
The aromatic part and intermediate chain
(slide 9)
For the composition of LA, what’s its:
pH:
Are they acids or bases?
pH: 6 (HCl salt)
WEAK BASE
(slide 10)
What 2 drugs if given with our LA can change its structure/composition?
Epinephrine
Sodium Bisulfite
(slide 10)
Which ester drug, Procaine or Tetracaine is more potent?
Tetracaine
(slide 11)
Which Amide has the highest protein binding%?
And what does this mean for how it will react in our body?
Levobupivavaine= >97%
The greater the protein binding = stays in the body longer (longer DOA)
(slide 11)
Any alteration in chemical structure leads to changes in ___________
Potency
Slide 11
Bupivacaine is 3-4x more potent than Mepivacaine. How does this affect the duration of action for Bupivacaine vs. Mepivacaine?
Bupivacaine has a longer duration of action because it is more potent than Mepivacaine
Slide 11
Drugs that have a pK value closer to body Ph have ____________ onset of action.
Faster
Slide 12
Which three drugs discussed in class have a pK value closely resembling normal body pH?
Lidocaine - 7.9
Prilocaine - 7.9
Mepivacaine - 7.6
Slide 12
What is the primary determinant of a local anesthetic’s potency?
Lipid solubility
Slide 13
What is used to upload higher amounts of LA into molecules and have consistent release of LA in the tissues?
Liposomes
Slide 14
Liposomes lead to ____________ duration of action and ___________ toxicity due to its timed release of local anesthetics.
Prolonged duration
Decreased toxicity
Slide 14
Local anesthetics inhibit passage into nerve membranes by binding to what type of channel?
Voltage Gated Sodium Channels
Slide 15
Local anesthetics need to be what form to go inside the cell and block the sodium channel?
Non-Ionized
Slide 15
Cocaine
- Ester or Amide?
- Metabolism?
- What populations is metabolism ⬇️ ?
- Ester
- Metabolized by the plasma & liver cholinesterases (the book says cocaine is one of the only LA that is SIGNIFICANTLY metabolized in the liver)
- Parturients (laboring mothers), neonates, Elderly, severe hepatic disease
Slide 37
Cocaine
Peak: ?
Duration: ?
Elimination: ?
What are you cautions with cocaine? (besides addiction)
Peak: 30-45 mins
Duration: 60 mins AFTER peak
Eliminations: Urine (24 - 36hrs)
Cautions: coronary vasospasm, ventricular dysrhythmias, HTN, tachycardia, CAD ❤️
Bupivacaine:
__% Protein Bound
____ arterial concentration
95% protein bound
0.32 arterial concentration
(slide 29)
Lidocaine:
__% protein bound
____ arterial concentration
70% protein bound
0.73 arterial concentration
(slide 29)
Prilocaine:
__% protein bound
____ arterial concentration
55% protein bound
0.85 arterial concentration
(slide 29)