Pharm Local Anesthetics

Front 1

Question: Properties of local anesthetics include?

Back 1

Increase in mm refractory period.

Blockade of voltage-dependent Na channels.

Effects on vascular tone.

Slowing of axonal impulse conduction.

Front 2

Question: The pKa of bupivicaine is 8.3. In infected tissue at pH 6.3, the percentage of the drug in the nonionized form will be?

Back 2

1%

Note: pKa = 50% is in the ionized and unionized form at that pH.

1 log unit different, ratio is approximately 90:10; at 2 units different, 99:1.

Front 3

Question: The onset of nerve blockade with local anesthetics is faster in?

Uninfected tissue vs. infected

Myelinated vs unmyelinated fibers

Hypercalcemia vs. hypocalcemia

Hyperkalemia vs. hypokalemia

Slower onset in the center of the bundle or periphery of a nerve bundle?

Back 3

Uninfected tissue

Myelinated

Hypocalcemia

Hyperkalemia

Note: Na channel blockers bind more readily to open or inactivated Na channels. Hyperkalemia depolarizes resting mm, so more inactive Na channels. Hypercalemia hyperpolarizes the resting potential, which reduces the block of Na channels.

Front 4

Question: The most important effect of inadvertent IV administration of a large dose of an amide local anesthetic is?

What can be used to counteract this?

Back 4

Seizures.

Note: Diazepam is commonly used for seizures.

Front 5

Question: Factors that influence the action of local anesthetics include?

Back 5

Tissue pH, use of vascoconstrictors, blood flow through the tissue where the injection occurs, and amount injected.

If allergic to ester base anesthetic, administer amide form.

Front 6

Question: You have a vial containing 8 mL of a 1% solution of lidocaine. How much lidocaine is present in 1 mL?

Back 6

10 mg.

Front 7

Question: With overdosage of a local anesthetic, hyperventilation (with O2) is helpful to correct?

Back 7

Acidosis and lower extracellular K.

Note: acidosis resulting from tissue hypoxia favors local anesthetic toxicity since these drugs bind more avidly form the Na channel binding site in the ionized form.

Front 8

Question: A vasoconstrictor added to a solution of lidocaine for a peripheral n. block will?

Back 8

Decrease the risk of a seizure and increase the duration of anesthetic action of local anesthetic.

Note: EPI causes vasoconstriction; therefore, increases the duration of the drug and less local anesthetic is required.

Front 9

Question: A child requires multiple minor surgical procedures in the nasopharynx. Which drug has high surface local anesthetic activity and intrinsic vasoconstrictor actions that reduce bleeding in mucous membranes?

Back 9

Cocaine.

Note: It is favored for head, neck, and pharyngal surgery.

Front 10

Question: A pregnant women was given an epidural anesthetic for pain relief during labor. The drug selected had a slow onset, but a longer duration of action than most of the other local anesthetics. Unfortunately, some of the drug was inadvertently injected via IV and caused marked drop in blood pressure and an arrhythmia. The drug used was most likely?

Back 10

Bupivacaine.

Front 11

Question: Prilocaine is relatively contraindicated in PTs with cardiovascular of pulmonary disease because the drug may do what?

Back 11

May cause decompensation through formation of methemoglobin.

Note: PTs may appear cyanotic and the blood "chocolate-colored"

Front 12

Many short acting local anesthetics are directly absorbed into the blood after injection, which limits its effectiveness. How can this be prevented?

What drug is an exception?

Back 12

Restriction of blood flow via a vasoconstrictor (e.g., alpha-agonist, such as epinephrine).

Cocaine doesn't need a vasoconstrictor since it has intrinsic sympathomimetic action due to its inhibition of NOR reuptake.

Front 13

What local anesthetic agents are esters and amides?

Back 13

Esters: Procaine, cocaine, tetracaine

Amides: lidocaine, bupivacine, prilocaine, mepivacaine.

Note: amides have two I's in their name.

Front 14

What is the MOA of local anesthetics?

Back 14

Blocks Na channels; therefore reduces influx of Na ions and depolarization.

Once inside the axon, the ionized form of the drug is more effective in blocking.

Front 15

Which one works more effective as a local anesthetics, ionized or nonionized form, and why?

Back 15

More lipid soluble, nonionized form.

Note: To reach their receptors in the cytoplasm, they have to cross lipid mm. However, once inside, the ionized form is more effective.

Front 16

Why are pain fibers selectively blocked by local anesthetics?

Back 16

Pain fibers = small and fire rapidly. Some of them are myelinated, while others are not.

Smaller fibers and myelinated fibers are blocked easier than larger, unmyelinated fibers. Rapidly firing fibers are blocked before slowly firing ones.

Front 17

Does cocaine produce elevated mood when used as a local anesthetic?

Back 17

No.

Note: Elevation of mood occurs from its affect on dopamine, not its action as an anesthetic on mm.

Front 18

What are the toxicity of local anesthetics?

What is the exception?

Back 18

CNS excitation (seizures); all cause vasodilation --> hypotension.

Cocaine can cause hypertension and arrhythmias.

Front 19

What local anesthetics can cause cardiovascular toxicity?

Back 19

Bupivacaine, such as arrhythmias and hypotension.

Front 20

Convulsions that occur from local anesthetics can be managed by?

Back 20

IV diazepam or short-acting barbiturate, such as thiopental.

Front 21

Since the local anesthetics are weak bases, how affective are they with an infection?

Back 21

Infected tissue is acidic; therefore, there will be more ionized (ineffective) vs. nonionized form of the drug.

The alkaline anesthetic will be charged with the infection, therefore, cannot penetrate the mm as effectively (more will be needed).

Front 22

What is prilocaine SE?

Back 22

Converts hemoglobin to methemoglobin.