Pharmacology VII

Question 1

What is the mechanism of action of local anesthetics?

Answer 1

Blocks sodium channels by binding to specific receptors on the inner portion of the channel; preferential binding to activated sodium channels making the drug most effective in rapidly firing neurons (p.454)

Question 2

How do tertiary amine local anesthetics penetrate membranes?

Answer 2

In uncharged form; they then bind to ion channels as charged form (p.454)

Question 3

What types of drugs are given along with local anesthetics to enhance local action?

Answer 3

Vasoconstrictors (usually epinephrine) (p.454)

Question 4

What effect do vasoconstrictors have when given along with local anesthetics?

Answer 4

Decrease bleeding, increase anesthesia, decrease systemic concentration (p.454)

Question 5

How does the amount of anesthetic needed vary with acidity of the tissue?

Answer 5

In infected (acidic tissue), alkaline anesthetics are charged and cannot penetrate the membrane effectively thus more anesthetic is needed (p.454)

Question 6

What is the order in which nerves are blockaded by local anesthetics?

Answer 6

Smal myelinated fibers> small unmyelinated fibers > large myelinated fibers > large unmyelinated fibers (p.454)

Question 7

What is the order of sensation loss due to local anesthetic action?

Answer 7

1) pain; 2) temperature; 3) touch; 4) pressure (p.454)

Question 8

What are local anesthetics used for?

Answer 8

Minor surgical procedures, spinal anesthesia (p.454)

Question 9

What toxicities are associated with use of local anesthetics?

Answer 9

CNS excitation, hypertension, hypotension (p.454)

Question 10

Name one toxicity specific to bupivacine when used as a local anesthetic.

Answer 10

Severe cardiovascular toxicity (p.454)

Question 11

Name one toxicity specific to cocaine when used as a local anesthetic.

Answer 11

Arrythmias (p.454)

Question 12

What are neuromuscular blocking drugs used for?

Answer 12

Muscle paralysis in surgery or mechanical ventillation (p.455)

Question 13

For which receptors are neuromuscular blocking drugs selective?

Answer 13

Motor (vs autonomic) nicotinic receptors (p.455)

Question 14

What are the two classes of neuromuscular blocking drugs?

Answer 14

Depolarizing and nondepolarizing drugs (p.455)

Question 15

What is the mechanism of action of succinylcholine?

Answer 15

A depolarizing neuromuscular blocking drug; strong Ach receptor agonist that produces sustained depolarization and prevents muscle contraction (p.455)

Question 16

Describe how neuromuscular blockade is reversed after use of depolarizing neuromuscular blocking drugs.

Answer 16

Phase I: no antidote; block is potentiated by cholinesterase inhibitors; Phase II: antidote consists of cholinesterase inhibitors (e.g. neostigmine) (p.455)

Question 17

Describe the mechanisms of the two phases of neuromuscular blockade.

Answer 17

Phase I: prolonged depolarization; phase II: repolarized channels, but blocked thus Ach receptors are available but are desensitized (p.455)

Question 18

What complications are associated with use of depolarizing neuromuscular drugs?

Answer 18

Hypercalcemia, hyperkalemia, malignant hyperthermia (p.455)

Question 19

Name six nondepolarizing neuromuscular blocking drugs.

Answer 19

Tubocurarine, atracurium, mivacurium, pancuronium, vecuronium, rocuronium (p.455)

Question 20

What is the mechanism of action of nondepolarizing neuromuscular blocking drugs?

Answer 20

Competitive antagonists that compete with Ach for receptors (p.455)

Question 21

What drugs are used to reverse the blockade associated with nondepolarizing neuromuscular blocking drugs?

Answer 21

Neostigmine, edrophonium, other cholinesterase inhibitors (p.455)

Question 22

What is the mechanism of action of dantroline?

Answer 22

Prevents the release of Ca2+ from the sarcoplasmic reticulum of skeletal muscle (p.455)

Question 23

What is dantroline used for?

Answer 23

Treatment of malignant hyperthermia (due to inhalation anesthetics and succinylcholine); can also be used to treat neuroleptic malignant syndrome (p.455)

Question 24

What is neuroleptic malignant syndrome?

Answer 24

A toxicity of antipsychotic drugs (p.455)

Question 25

What is the basic pathophysiology of Parkinson’s disease?

Answer 25

Loss of dopaminergic neurons and excess cholinergic activity (p.455)