Local Anesthetics Flashcards
How do local anesthetics work?
reversible loss of sensation in a localized part of the body when applied directly onto nerve tissues or mucous membranes.
Block generation and conduction of nerve impulses at a localized site of contact without structural damage to neurons.
What is the clinical use of LA?
to block pain sensation from specific areas of the body
through Loss of sensory and motor impulses
What are some clinical examples of LA use?
Topically for wound and margins (edges or borders of a wound)
Infiltration into Vicinity of peripheral nerve endings and
major nerve trunks
Epidural or Subarachnoid spaces: surrounding
spinal nerves
Regional anesthesia via Intravenous injection in arm or leg
What is subarachnoid space?
area between the arachnoid mater and the pia mater in the brain and spinal cord. It is filled with cerebrospinal fluid (CSF)
General anesthesia acts on the CNS while LA act on ________ _______
GA acts on the ________ _______ while LA acts on restricted areas.
peripheral nerves
whole body
You lose consciousness with GA, but remain awake with LA.
T/F
You need to care for vital functions when giving GA
T
T
What is EMLA?
Give an example?
What are the characteristics of a eutectic mixture?
Eutectic Mixture of Local Anesthetics
e.g. Lidocaine and prilocaine
Equal amount by mass of two solid substances mixed and melting point of mixture is lower than both substances.
What is lidocaine and prilocaine an example of?
Describe the mixture?
What are the classifications of these two anesthetics?
EMLA
oily
Lidocaine and prilocaine are both intermediate potency Lidocaine is a surface anesthetic
What is mixture of lidocaine and prilocaine used for?
- for dermal anaesthesia
- to prevent pain associated with intravenous catheter insertion, blood sampling, superficial surgical procedures
- topical anaesthesia of leg ulcers for cleansing or debridement
- numb the skin before tattooing
- cream used in the treatment of premature ejaculation.
What is Lidocaine?
also called Xylocaine.
Remember this is the most commonly used LA.
- Classification
- Routes of administration
- Dosage forms
- Compare to procaine.
- Intermediate potency surface anesthetic
- Routes (all): topical, infiltration, spinal.
3 So available as Injections, topical solutions, jelly and ointment. - Faster onset, more intense and longer duration than procaine.
What is Lidocaine?
also called Xylocaine.
Remember this is the most commonly used LA.
- What does adding Adrenaline do?
- Side effects
- Overdose symptoms
- Also used an an _____________
- Adding Adrenaline (1:200 000) prolongs action for 2hrs.
- Quicker CNS effects (drowsiness, mental clouding, altered taste and tinnitus)
- Overdose (muscle twitching, cardiac arrhythmia, fall in BP, coma and respiratory arrest)
- Antiarrhythmic
What is Bupivacaine?
Also called Marcaine.
- Classification
- Routes
- Use
- Side effects
- slower onset, High potency, long duration (8hrs)
- Not given topical, IV
- Used spinal, infiltration
- For nerve block, epidural, analgesia during labor (because it doesn’t cause motor blockade)
- more cardio-toxic due to prolonged QT interval
Compare the onset and duration with adrenaline for the following LA, procaine, lidocaine and bupivacaine.
Procaine and bupivacaine have slow onsets.
Lidocaine has rapid onset
With adrenaline procaine has a 45-90 min duration.
Lidocaine 2-4 hrs
bupivacaine 4-8 hrs
PK of LA refers to Absorption and distribution.
- What are the factors affecting absorption?
- Comment on the absorption of procaine in mucus membranes.
- How does procaine and amides bind to plasma proteins
1.Blood flow to the area, total dose and specific drug characteristics.
2. Procaine has poor penetration in mucus membrane
3. Procaine negligibly bound to plasma protein but amides are bound to alpha 1 acid glycoprotein
PK of LA refers to Absorption and distribution.
- Are La lipophilic or hydrophilic? How does this affect distribution in the body?
- Lipophilic so widely distributed in the body.
Enters brain, heart, liver and kidney, followed by muscle and other viscera
