Local Anesthetics Flashcards
MOA of Local Anesthetics
Bind and block Na+ voltages-gated channels to not allow propagation of signal - NON-SELECTIVE
Block channels in the open/inactivated state
T/F: The action of Local Anesthetics is terminated by redistribution
True: Use vasoconstrictors (epinephrine) to decrease distribution away from the site of action
Ester LA
Rapidly broken down by plasma pseudocholinesterases
Amide LA
Mainly metabolized by the liver
T/F: Motor transmission is blocked before pain and sympathetic transmission
False:
Pain and sympathetic transmission are blocked before motor transmission
List the order in which fibers are blocked: A-alpha fibers, A-delta fibers, C fibers
A-delta fibers
A-alpha fibers
C fibers
T/F: The potency increases by increasing lipid and water solubility
True
T/F: The higher the pKa, the more unionized drug enters the axon
False:
The LOWER the pKa, the more unionized drug enters the axon
Which LA are part of the Ester subclass?
Procaine Benzocaine Proparacaine Tetracaine Way to remember: All Esters only have one "i" in their name; All Amides have two "i" in their name
Which LA are part of the Amide subclass?
Lidocaine Bupivicaine Mepivacaine Prilocaine Ropivacaine Dibucaine Way to remember: All Esters only have one "i" in their name; All Amides have two "i" in their name
Clinical uses of Procaine
DO NOT USE THIS DRUG
Regional anesthesia
Dx lameness in horses
Ventricle arrhythmia (DONT USE WITH EPINEPHRINE)
Clinical uses of Benzocaine
Topical absorption in fish only
Clinical uses of Proparacaine
Topical corneal and conjunctival manipulation
Clinical uses of Tetracaine
Topical corneal and conjunctival manipulation
Euthanasia with Embutramide
Clinical uses of Lidocaine
Endotracheal intubation in cat
IM with Oxytetracycline (because it’s painful)
Euthanasia with Embutramide
MOST common LA in vet med
Clinical uses of Bupivacaine
Nerve block
Epidural (does not work topically)
Second most widely used LA
Clinical uses of Mepivacaine
Nerve block
Dx lameness in horses
Clinical uses of Prilocaine
IV regional anesthesia
Clinical uses of Ropivacaine
Nerve block
Dx lameness in horses
Clinical uses of Dibucaine
Euthanasia with Secobarbital
Contraindications for Procaine
DO NOT USE THIS DRUG
Sulfonamide use
Toxic to horses
Contraindications for Lidocaine
Do NOT use in food animals
Metabolite is considered carcinogenic
Contraindications for Bupivacaine
MOST cardiotoxic
Special considerations for Procaine
DO NOT USE THIS DRUG SLOW ONSET, SHORT DURATION Rapidly metabolized to PABA Slows PenG absorption from muscle CNS stimulation in horses - TOXIC Horses are the most sensitive species
Special considerations for Benzocaine
LOWEST pKa (2.5) - ionized and low solubility
Special considerations for Proparacaine
RAPID ONSET (30 sec.) and SHORT DURATION (10-20 min) LESS irritating than Tetracycline
Special considerations for Tetracaine
LONGER duration than Proparacaine
Intrathecal
Special considerations for Lidocaine
RAPID ONSET (5 min) and MEDIUM DURATION (40-60 min) Used parenterally or topically Max dose = 7mg/kg - sheep most sensitive
Special considerations for Bupivacaine
SLOW ONSET (20 min) and LONGEST DURATION (8 hrs) Max dose = 2mg/kg
Special considerations for Mepivacaine
LESS irritating than Lidocaine
Special considerations for Prilocaine
SIMILAR to Lidocaine but LESS toxic to cardiac muscle
Emla cream - 20-30 min to full effect (dermal analgesia)
Special considerations for Ropivacaine
SIMILAR to Bupivacaine but has SHORTER DURATION and LESS toxic
Special considerations for Dibucaine
MOST potent and MOST toxic LA
T/F: All Esters cause methemoglobinemia
True
T/F: All Esters cause histamine release
True:
Histamine release caused by PABA
