Local Anesthetics Flashcards
What is the most widely used anaesthetic?
Lidocaine
What local anaesthetic is cardiotoxic?
Bupivacaine
Which local anaesthetic is contraindicated in obstetric anaesthesia?
Mepivacaine
Why is Mepivacaine contraindicated in obstetric anesthesia?
Due to its increased toxicity to neonates
What is the clinical use of local anaesthetics?
Complete loss of sensory modalities
Analgesia
What is the target of local anaesthetics?
Inactivated voltage gated sodium channels
What part of the voltage gated sodium channel do local anaesthetics bind to?
The IC part
Which drugs bind to the EC part of the activated voltage gated sodium channel?
Tetrodotoxin
Saxitotoxin
What are the three states of the voltage gated sodium channel?
Resting state
Inactivation state
Activation state
What are the M and H gate doing during resting state?
M gate is closed
H gate is open
What are the M and H gate doing during the activation state?
Both gates are open
What are the M and H gate doing during the inactivation state?
The M gate is open
The H gate is closed
What is the M gate?
The activation gate
What is the H gate?
The inactivation gate
What are the methods of administration of local anaesthetics?
Surface Infiltration IV Peripheral nerve blocks Spinal Epidural
What is the order of disappearance of sensations?
- Pain
- Temperature
- Touch
- Deep pressure
- Motor function
What nerve fibres are most sensitive to blockage?
Nerve fibres off small diameter and high firing rates
What is the order of sensitivity of the nerve fiber types?
Type B and C
A delta
A beta and gamma
A alpha
What are the CNS side effects of local anaesthetics?
Headache Sleepiness Visual and auditory disturbances Restlessness Nystagmus Shivering Muscular twitching Seizures Depression Death Cocaine: feeling of well being, psychostimulant, euphoria
What are the cardiovascular side effects of local anaesthetics?
Depression of pacemaker activity, condition, excitability, contractility
Vasodilation - hypotension
Cocaine: vasoconstriction
Why is a side effect of local anaesthetics allergies?
Esters viva PABA formation
Sulfonamides are esters of PABA
What are the haematological side effects of local anaesthetic use?
Prilocaine can result in methemoglobinemia
Can local anaesthetics cross the placenta?
Local anaesthetics may cross the placenta
What are the (broad) side effects of local anasthetic use?
CNS effects Cardiovascular toxicity Allergies Haematological effects Local anaesthetics may cross the placenta
What is Ropivacaine metabolised by?
CYP1A2
What enzyme is Lidocaine and Bupoivacaine metabolised by?
CYP3A4
What are the general categories of LI?
Esters and amides
Name the ester LA?
Procaine
Cocaine
Benzocaine
Name the amide LA?
Lidocaine Prilocaine Bupivacaine Ropivacaine Mepivacaine Atricaine
What are the esters metabolised by?
Plasma and tissue esterases
What are the amides metabolised by?
Liver amidases
What is the potency of procaine?
1
What is the potency of bupivacaine?
16
What is the potency of Mepivacaine?
2
What is the potency of Atricaine?
10
Which LA is the most potent?
Bupivacaine
Which LA is the least potent?
Procaine
Which LA have a short duration of action?
Procaine
Atricaine
Which LA have a medium duration of action?
Cocaine
Lidocaine
Prilocaine
Mepivacaine
Which LA have a long duration of action?
Benzocaine
Bupivacaine
Ropivacaine
Which LA have poor tissue penetration?
Procaine
Which LA have moderate tissue penetration?
Prilocaine
Bupivacaine
Ropivacaine
Which LA have good tissue penetration?
Cocaine
Lidocaine
Mepivacaine
Atricaine
What is the clinical indication of procaine?
No longer used
What is the clinical indication of cocaine?
Rarely used. Only as a spray for upper respiratory tract
What is the clinical use of Benzocaine?
Surface anesthesia
What is the clinical use of lidocaine?
Local anaesthesia but also IV for treating ventricular dysrhythmias
What is the clinical use of prilocaine?
Spinal anesthesia
Not used for obstetric analgesia
What is the clinical use of Ropivacaine?
Spinal anesthesia
Not used for obstetric analgesia
What is the clinical use of Mepivacaine?
Infiltration and nerve block anesthesia
Mild vasoconstrictor effect
Not used in babies or small children
What is the clinical use of Atricaine?
Infiltration and nerve block anesthesia
More lipophillic
Used in dentistry
What are the cardiovascular side effects of procaine?
Bradycardia and vasodilation
What are the adverse CNS effects of procaine?
Restlessness
Convulsions
Respiratory depression
What are the adverse effects of prilocaine?
No vasodilator activity
Less risk of systemic toxicity but risk of methemoglobinemia