Pharm - Local Anesthetics
An anesthetic is a drug to prevent pain during surgery, completely blocking any feeling as opposed to an analgesic. Propofol is one of the most commonly used intravenous drugs employed to induce and maintain general anesthesia. Take this Pharmacology test on local anesthetics and remind yourself of what you covered in your class this month.
- 1.The primary mechanism of action of local anesthetics involves the blockade of which of the following ion channels?
- A.
Inactivated, voltage-gated, Na+ channels
- B.
Resting, voltage-gated ,K+ channels
- C.
Activated, ligand-gated, Ca++ channels
- D.
Inactivated, ligand-gated, K+ channels
- E.
Resting, ligand-gated, Na+ channels
- F.
Activated, voltage-gated, Ca++ channels
- 2.Which of the following nerve fibers are most sensitive to the action of local anesthetics?
- A.
Resting fibers
- B.
Rapidly firing fibers
- C.
Fibers with high conduction velocity
- D.
Unmyelinated fibers
- E.
Fiber of large diameter
- 3.When a local anesthetic is applied to a nerve fiber, which of the following nerve properties will most likely increase?
- A.
Rate of rise of the action potential
- B.
Amplitude of the action potential
- C.
Refractory period of the nerve
- D.
Conduction velocity of the nerve
- E.
Resting potential of nerve membrane
- 4.Which of the following functions is blocked last when a local anesthetic is applied to a nerve?
- A.
Motor function
- B.
Pain sensation
- C.
Muscle tone
- D.
Pain sensation
- E.
Vasomotor function
- 5.Which of the following molecular events makes the nerve membrane more sensitive to the action of local anesthetics?
- A.
Increased extracellular concentration of Ca++
- B.
Increased extracellular concentration Na+
- C.
Decreased extracellular concentration of Cl-
- D.
Increased extracellular concentration of K+
- E.
Increased extracellular concentration of Mg++
- 6.A main feature of the mechanism of action of local anesthetics is a voltage dependent blockade of Na+ channels. Which of the following statements best explains this voltage dependency?
- A.
The more negative the membrane potential, the lower the affinity for local anesthetics
- B.
The more negative the membrane potential, the higher the affinity for local anesthetics
- C.
The higher the frequency of firing of the fiber, the lower the affinity for local anesthetics
- D.
The lower the frequency of firing of the fiber, the higher the affinity for local anesthetics
- E.
The faster the conduction velocity of the fiber, the higher the affinity for local anesthetics
- 7.The ionized form of local anesthetics is mainly responsible for which of the following properties of the drug?
- A.
Tissue redistribution
- B.
Liver biotransformation
- C.
Systemic toxicity
- D.
Receptor binding
- E.
Half-life
- 8.Which of the following statements best explains why the onset of the therapeutic effect of a local anesthetic is usually slower in infected tissues?
- A.
They are very rich in drug-metabolizing enzymes
- B.
They are poorly vascularized, so that the drug reach slowly the nerve terminals
- C.
They are rich in extracellular K+ which lower the drug-receptor binding
- D.
They are rich in PABA which is a competitive antagonist of most local anesthetics
- E.
They have a low extracelluar pH, which hinders the drug diffusion into the cell
- 9.The pKa of lidocaine is 7.9. Which fraction of the drug will be in the lipid soluble form in the extracellular fluids (pH = 7.4)?
- A.
10%
- B.
24%
- C.
50%
- D.
76%
- E.
90%
- 10.Which of the following local anesthetics is mainly metabolized by the liver?
- A.
Cocaine
- B.
Bupivacaine
- C.
Procaine
- D.
Tetracaine
- E.
Benzocaine
- 11.Which of the following is the most cardiotoxic local anesthetics drug?
- A.
Benzocaine
- B.
Procaine
- C.
Tetracaine
- D.
Lidocaine
- E.
Bupivacaine
- 12.A 14-year-old boy complained of burning pain due to multiple superficial skin abrasions, after a motorcycle accident. Which of the following local anesthetics would be appropriate for this boy?
- A.
Benzocaine
- B.
Procaine
- C.
Cocaine
- D.
Prilocaine
- E.
Bupivacaine
- 13.Which of the following are the main purposes for adding a vasoconstrictor drug to a local anesthetics? (Check all that apply)
- A.
To speed up the onset of the anesthetic effect
- B.
To increase the duration of anesthetic effect
- C.
To decrease the risk of systemic overdose toxicity of the drug
- D.
To decrease the risk of allergic reactions of the drug
- E.
To increase the affinity of the drug for the Na+ channels
- 14.Which of the following systems are more likely involved, when a toxic dose of local anesthetic is inadvertently given IV? (Check all that apply)
- A.
Gastrointestinal system
- B.
Respiratory system
- C.
Urinary system
- D.
Immune system
- E.
Cardiovascular system
- F.
CNS
- 15.A 25-year-old pregnant woman who is near term decides to have the delivery under spinal anesthesia. Past history of the patient include an anaphylactic reaction 3 years ago apparently due to a sun screen cream containing para-aminobenzoic acid. Which of the following local anesthetic would be appropriate for this patient?
- A.
Procaine
- B.
Tetracaine
- C.
Lidocaine
- D.
Benzocaine
- E.
Prilocaine
- 16.A 65-year-old man is scheduled for a lithotripsy to shatter a bladder stone. The lumbar epidural anesthesia is selected for the procedure. Since the anticipated duration of the procedure is about 30 minutes which of the following drug should be used?
- A.
Cocaine
- B.
Procaine
- C.
Benzocaine
- D.
Tetracaine
- E.
Lidocaine
- 17.A 43-year-old patient underwent an emergency minor arm repair procedure after a car accident. A standard dose of lidocaine was administered near the brachial plexus for peripheral nerve block. Which of the following adverse effects would most likely occur after the administration?
- A.
Ventricular tachycardia
- B.
Abdominal colic
- C.
Drowsiness
- D.
Tonic-clonic convulsions
- E.
Disorientation
- 18.A 56-year-old woman, who has been suffering from atrial fibrillation for 3 years, is in the dentist’s office for the application of an implant. The dentist is about to initiate a local anesthesia by injecting a local anesthetic close to the mandibular nerve. Which of the following local anesthetic preparations should be chosen by the dentist for this patient?
- A.
Lidocaine
- B.
Lidocaine plus epinephrine
- C.
Bupivacaine plus epinephrine
- D.
Benzocaine plus epinephrine
- E.
Benzocaine
- 19.A 15-year-old boy was undergoing an emergency leg repair after a motor related injury. The anesthesiologist injected a drug near the radial nerve. Which of the following was most likely the molecular mechanism of action of the injected drug?
- A.
Blockade of substance P receptors in the injured area
- B.
Blockade of Na+ channels in the radial nerve membranes
- C.
Activation of alpha-2 presynaptic receptors in the radial nerve terminals
- D.
Activation of opioid receptors in the injured area
- E.
Blockade of prostaglandin receptors in the injured area
- 20.A 34-year-old man was scheduled to undergo open repair of multiple fractures in one hand. The anesthetic management was brachial plexus anesthesia with bupivacaine. During the injection of the anesthetic the patient suddenly exhibited nystagmus, slurred speech, tremors, muscle twitching, followed by tonic-clonic convulsions. Which of the following statements best explain the neurophysiologic mechanism of the excitatory state Induced by the drug in this patient?
- A.
The drug caused cardiotoxic effects which in turn triggered the CNS excitation
- B.
The drug mediated an allergic reaction in a sensitized patient
- C.
The drug inhibited glutamate reuptake into glutamatergic neurons
- D.
The drug activated the mesolimbic pathway in the CNS
- E.
The drug caused depression of the inhibitory neurons in the CNS
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