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Local Anaesthetics (Cocaine :fire: (Uses (Low concentration - for eyes,…
Local Anaesthetics
Cocaine
:fire:
An
ester
local anaesthetic
Topical
use only
Lead to toxicity if use systemically
Rapid
onset (1 minute) and fairly long duration of action (2 hours)
Uses
Low
concentration - for
eyes
Nasal and pharyngeal mucosa
:check:
Produce euphoria
Cortical stimulation
Adverse effects
At high dose - cause
cardiac failure
:!:
Produce
euphoria and stimulant effect
even at low dose
:!!:
Benzocaine
:red_flag:
Ester - PABA derivative
Uses
Topical
application on skin and mucous membrane
Highly lipophilic
Stay at site of action longer
Lower incidence of systemic toxicity
Contraindication -
Hypersensitivity
towards PABA-containing compounds :!:
Chloroprocaine
:warning:
Ester - procaine derivative
More potent and less toxic than procaine
Hydrolyzed rapidly by cholinesterase
short plasma half-life
Use
Obstetrics
Safe to use in neonates :check:
Procaine
:checkered_flag:
Ester
Hydrolyzed by cholinesterase and undergoes hepatic metabolism
Not effective topically - for
infiltration, nerve block and spinal anaesthesia
:check:
Slow
onset of action and short duration of action
Use along with
epinephrine
/
phenylephrine
(in dentistry)
produce vasoconstriction - for procaine to stay longer at the site of action
Tetracaine
:explode:
ester -PABA
aware of
hypersensitivity
Topical
- used as
spinal/subarachnoid block
Use along with
epinephrine
prolong anaesthesia by vasoconstriction
More toxic
than cocaine and procaine
Lignocaine/Lidocaine/Xylocaine
:<3:
Amide
Most commonly used
Uses
Infiltration and topical
Spinal/subarachnoid anaesthesia
Regional nerve block
Antiarrhythmic
Long
duration of action
Bupivacaine
:star:
Long
duration of action (>24 hours!)
Uses
Lumbar
epidural
anaesthesia
for
obstetrics
:check:
Analgesia
effect
Motor activity - aid in
expelling the foetus
Spinal
anaesthesia
Cautious of
cardiac toxicity
:red_cross:
use lower concentration to avoid it
More potent and toxic
than mepivacaine and lidocaine
can be used without epinephrine
Amide
S-enantiomer
Levobupivacaine
:star:
Less CNS and cardiac toxicity
but more motor sparing
Ropivacaine
:recycle:
Amide
Long-acting
Can be used with other amide LA
Less cardio-toxicity
Etidocaine
:lock:
Amide
Epidural
anaesthesia
Preference for
motor
block rather than sensory block
Mepivacaine
:black_flag:
Longer duration of action than lidocaine
Rapid onset of action
Amide
Side effects
Early transient neurobehavioral effects :!:
Prilocaine
:unlock:
Amide
Longer action and less toxic than lidocaine
Convert haemoglobin to methemoglobin
at high dose :!:
due to accumulation of
ortho-toluene
oxygen transport is impaired :!!:
resolved by using
methylene blue
(reducing agent)