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17 Cards in this Set
- Front
- Back
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What were the problems with thte first synthetic LA?
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- Long onset of action
- Ester group thus allergic response - Short acting |
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What are benefits of Lidocaine?
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- Amide group: hypoallergenic
- Fast acting - Long lasting effects |
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Why is Lidocaine given with adrenaline?
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It causes vasoldilation - adrenaline reverses these effects and localises the effects
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What are the 3 structural requirements of LAs?
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- Hydrophobic group
- Hydrophilic group - Intermediate bond (ester/amide) |
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What is Pka?
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PH at which concentration of [ionised] and [unionised] LA is the same
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What receptors are the targets of LAs?
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Na channels
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Describe the hydrophobic pathway
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Unionised form of the drug enters membrane of axon and 'side steps' into pore of receptor (whether open/closed/inactive)
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Describe the hydrophilic pathway
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Ionised form of drug enters when the channel is open (use dependent) and binds to inner pore
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Are LAs more active in acidic or alkaline pH?
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Alkaline
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What is the physiological pH?
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7.4
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What is pH like at infected sites of tissue?
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acidic
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LAs with lower pKa values are..more/less ionised?
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Less
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LAs with low pKa...
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Better absorbed in nerve tissue (less ionised) but may be difficult to interact with binding site in Na channel
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LAs with high pKa...
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More ionised thus takes longer to take effect but more effective at blocking Na channel
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LAs with higher or lower pKa is more efficient at blocking Na channel?
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Higher
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Are motor neurons affected by LAs?
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No - LAs take effect on small diameter afferent neurons
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Reasons for choosing LA over GA?
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- Less nausea felt
- Long lasting effects even after surgery - May reduce blood loss |
