Author Question: The patient has a diagnosis of multiple sclerosis and is taking the drug interferon beta-1a (Rebif). ... (Read 76 times)

jake · **on:** Jul 23, 2018

The patient has a diagnosis of multiple sclerosis and is taking the drug interferon beta-1a (Rebif). The patient takes this drug by subcutaneous injection three times a week. The dosage is 44 mcg per injection.

If the patient takes an injection on Monday, how much of the drug would still be in the patient's system when she takes her next injection on Wednesday, assuming the half-life of the drug is 24 hours? A) 22 mcg
B) 16.5 mcg
C) 11 mcg
D) 5.5 mcg

Question 2

A patient diagnosed with bipolar disorder is to be discharged home in 48 hours. The nurse has completed patient teaching regarding the use of lithium. What statement by the patient indicates an understanding of their responsibility?

A) I will increase my salt intake.
B) I will increase my fluid intake.
C) I will decrease my salt intake.
D) I will decrease my fluid intake.

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

Answer to Question 1

C
Feedback:
The half-life of a drug is the time it takes for the amount of drug in the body to decrease to 1 half the peak level it previously achieved. On Tuesday, there would be 22 mcg remaining in the body, so option A is incorrect. On Wednesday 11 mcg would remain, so option C is the correct answer. At 12 hours before taking the next dose on Wednesday, there would be 16.5 mcg remaining. If the injection were not taken on Wednesday, 12 hours after the dose was due, there would be 5.5 mcg remaining.

Answer to Question 2

B
Feedback:
To maintain a therapeutic lithium level, the patient must increase fluids. A decrease in consumption of fluids can lead to toxicity. An increase in salt intake can lead to lithium excretion and a decrease in effectiveness. A decrease in salt intake can cause retention, also leading to toxicity. Adequate salt intake is necessary to keep serum levels in therapeutic range but need not be increased or decreased.