A patient reports becoming immune to a medication because it no ...

[lak]

A patient reports becoming immune to a medication because it no longer works to alleviate symptoms. The nurse recognizes that this decreased effectiveness is likely caused by:
 
  a. antagonists produced by the body that compete with the drug for receptor sites.
  b. decreased selectivity of receptor sites, resulting in a variety of effects.
  c. desensitization of receptor sites by continual exposure to the drug.
  d. synthesis of more receptor sites in response to the medication.

Question 2

A prescriber has written an order for a medication: drug X 100 mg PO every 6 hours. The half-life for the drug is approximately 6 hours. The nurse is preparing to administer the first dose at 8:00 AM on Tuesday.
 
  On Wednesday, when will the serum drug level reach plateau?
  a. 2:00 AM
  b. 8:00 AM
  c. 2:00 PM
  d. 8:00 PM

[ApricotDream]

Answer to Question 1

ANS: C
Continual exposure to an agonist would cause the cell to become less responsive or desensitized. The body does not produce antagonists as a response to a medication. Receptor site selectivity is determined by physiologic factors and not by the substances that bind to them. Medications do not cause more receptors to be produced.

Answer to Question 2

ANS: B
It takes four half-lives for a drug to reach plateau. Total body stores reach their peak at the beginning of the fifth dose of a drug if all doses are equal in amount; in this case, this will be at 8:00 AM the following day.

[lak]

Thanks for the timely response, appreciate it

[chereeb]

TYSM