Pharm: Local Anesthetics Flashcards
What is the importance of an amide vs. an ester bond in the local anesthetics?
Ester bonds are hydrolyzed much quicker in water and will therefore have a shorter half life.
How is hydrophobicity important for the pharmacologic activity of the local anesthetics?
Hydrophobicity allows a drug to cross the cell membrane which is necessary for efficacy. Too hydroPHILIC and the drug won’t cross the membrane. Too hydroPHOBIC and the drug will cross the membrane but will remain in the membrane and not enter the cytosol to have effect.
What is the importance of the tertiary amine group in the local anesthetics?
In order for local anesthetics to form a strong bond to the receptor on which they act, the tertiary amine lone pair must bind a hydrogen to put a (+) charge on the nitrogen. So a lower extracellular pH with more protons increases the POTENCY of the drug.
(BZ are permanently un-ionizable and don’t bind to the GABA receptor with very high affinity)
What is a side effect that generally occurs with aminoesters?
Allergic Reaction
What is the general MOA for the local anesthetics?
Blockade of voltage-gated sodium, potassium, and calcium channels along the neuronal axon. High affinity for binding the channels in the: inactive, open, and closed states.
Low affinity for binding the channel in the resting state.
This just means that the drug will have more action in neurons that are firing impulses at a high rate. (increases selectivity toward neurons sending a lot of pain signals)
(autonomic and opioid receptors can be affected too)
What is the primary neurotransmitter released in neurons that send pain signals in the CNS?
Glutamate
What is TAC used for?
TAC: tetracaine, adrenaline (epi), cocaine
applied before suturing small wounds and cuts
In dentistry, which two local anesthetics are applied topically and why?
Lidocaine and benzocaine b/c they have poor water solubility and low risk of disseminating into the systemic circulation.
Which local anesthetic is injected for shorter dental procedures because of its fast action and slightly longer duration? Also required a vasoconstrictive agent to keep the drug localized.
Lidocaine
Which local anesthetic is injected for dental procedures but has little vasodilation effect and therefore can be administered without a vasoconstrictive agent?
Mepivacaine
Which local anesthetic has a long half life and is used for long dental procedures and post-op pain?
Bupivacaine
Name the main local anesthetic administered in epidurals and one adverse effect.
Bupivacaine
-may cause cardiotoxicity
(ropivacaine and levobupivacaine are newer and may be safer)
What type of local anesthetic is best for Intravenous Regional Anesthesia?
Short acting like lidocaine
-disadvantage is that there is a time limit on the procedure and the physician must work fast
What is the main application of procaine?
Dental procedures.
PABA is a metabolite that causes allergic reactions and interferes with sulfonamide drugs
What is tetracaine mainly used for and why does it have a longer half-life than the other aminoester local anesthetics?
Spinal and topical anesthesia
-it is very hydrophobic which increases its half-life
