Pharmacology Flashcards
What are the effects of Local anaesthetics?
- Slow rate of depolarization.
- Slow axonal conduction
- Increase threshold potential.
- Reduce height of action potential.
- No effect on RMP
“SSIR No”
What is the mechanism of action for local anaesthetics?
Physical blockade of voltage gated Na+
What happens when local anaesthetics provides a physical blockade for Na+ channels?
Blockade Increase Na+ channel recovery time (10-1000 times)= prolonged refractory period Ultimately prevent propagation of AP
What are examples of Esters?
Please - Procaine
Bring - Benzocaine
The- Tetracaine( Amethocaine)
Cocaine
” Please bring the cocaine”
What are examples of Amides?
Roy - Ropivacaine
Brought - Bupivacaine
Pain - Prilocaine
Medication - Mepivacaine
Late- Lignocaine
Which local aesthetic drugs are weak bases (pKa 8-9) (poor solubility in water) & given as HCl salts, water soluble?
Procaine
Lignocaine
Benzocaine
Where is the receptor site for local anaesthetics located?
On the innerside of the membrane
True or False? Local anaesthetics bind most avidly to the activated state of sodium channels.
FALSE!! They bind most avidly to the INACTIVATED state .
True or False? The greater the firing frequency of an axon, the greater the blockade.
TRUE!!
True or False? Local anaesthetics DOES NOT promote hyperpolarization.
TRUE!!
Why do local anaesthetics have no effect on the resting membrane potential?
This is because the resting membrane potential; is controlled by the sodium potassium ATP-ase NOT Voltage- gated Sodium channels
True or False? In regards to local anaesthetics, The larger the diameter of the nerve the greater the susceptibility.
FALSE!! The smaller the diameter of the nerve the greater the susceptibility
Which fibers are most sensitive to block for local anaesthetics?
Type C fibres
True or False? The closer the pka is to 7.4 , the faster the onset of the drug.
TRUE!!
What are factors that will affect the use of local anaesthetics?
- Acidic environment facilitates the population of the charged form
- Basic environment is low in H ions and facilitates the free base
True or False? Local Anaesthetics does NOT react faster if there is inflammation at the site.
TRUE!! Local anaesthetics does NOT react faster if there is a site of inflammation due to its acidic environment so the antilog is MORE and there will be less BASE form so the drug will work less and even have more adverse effects .
Which local anaesthetic drug was the first to be discovered?
Cocaine was the first local anaesthetic drug to be discovered
By what process do local anaesthetics enter the body through?
Passive diffusion
Which local anaesthetic drug is applied ONLY Topically ?
Benzocaine
By what enzyme are Local Anaesthetics (ESTERS) metabolised & eliminated?
By the enzyme plasma pseudocholinesterases to produce Para-aminobenzoic acid (PABA).
True or False? Local anaesthetics ( AMIDES) are metabolised through the kidneys.
FALSE!! Hepatic metabolism so liver
Which Local anaesthetic ( ESTERS) is NOT metabolised by the enzyme plasma pseudocholinesterases to produce Para-aminobenzoic acid (PABA)?
COCAINE- It goes through Hepatic metabolism
Which local aesthetic drug is associated with causing Methemoglobinaemia due to production of toluidine on metabolism?
Prilocaine
Allergic reactions are seen with which type of local anaesthetics?
Esters - due to PABA from metabolism.
Fill in the blanks. “ Most local anaesthetics are vasodilators EXCEPT ___________ which is a Vasoconstrictor.”
Cocaine = Vasoconstrictor
What are the adverse effects of Cocaine?
CV= -vasoconstriction, increase BP, Arrhythmias
CNS = Euphoria