Author Question: What class of antiarrhythmics drug blocks potassium channels, prolonging phase 3 of the action ... (Read 54 times)

lindiwe · **on:** Jul 23, 2018

What class of antiarrhythmics drug blocks potassium channels, prolonging phase 3 of the action potential and slowing the rate and conduction of the heart?

A) I
B) II
C) III
D) IV

Question 2

A 3-year-old girl with a diagnosis of spasticity caused by cerebral palsy has been admitted to the unit. The physician has ordered dantrolene to see if it relieves the spasticity in the child's arms and hands.

The nurse would schedule this child for what routine screenings? A) Central nervous system and gastrointestinal (GI) function
B) Respiratory and cardiovascular (CV) function
C) Growth and development
D) Renal and hepatic function

dlook33 · **Reply #1 on:** Jul 23, 2018

Answer to Question 1

C
Feedback:
The class III antiarrhythmics block potassium, prolonging phase 3 of the action potential, which prolongs repolarization and slows the rate and conduction of the heart. Class I drugs block the sodium channels in the cell membrane during an action potential. Class II drugs are beta-adrenergic blockers that block beta-receptors, causing a depression of phase 4 of the action potential. Class IV drugs block calcium channels in the cell membrane leading to a depression of depolarization and a prolongation of phases I and II of repolarization, which slows automaticity.

Answer to Question 2

A
Feedback:
Children prescribed dantrolene should be routinely and regularly screened for central nervous system and gastrointestinal (including hepatic) toxicity. Growth and development should be routinely screened in all children. Renal, respiratory, and CV screening is not indicated.