Author Question: A client has been started on diltiazem (Cardizem), a susbstrate of the cytochrome CYP3A4 isoenzyme ... (Read 59 times)

javeds · **on:** Jul 23, 2018

A client has been started on diltiazem (Cardizem), a susbstrate of the cytochrome CYP3A4 isoenzyme system. The client also takes phenobarbital, an inducer of the CYP3A4 isoenzyme system, for seizures. What does the nurse recognize about diltiazem?

1. It will not be able to cross the blood brain barrier (BBB).
2. It will be metabolized by the kidneys.
3. It might be inactivated at a faster rate than normal.
4. It might be excreted at a slower rate.

Question 2

A client receiving metoprolol (Lopressor), a substrate of the CYP2D6 system, is started on amiodarone (Cordarone), an inhibitor of the CYP2D6 system. What should the nurse plan to do?

1. Monitor for signs of amiodarone toxicity.
2. Administer both drugs on an empty stomach.
3. Monitor for prolonged effects of the Lopressor.
4. Administer the medications at least two hours apart.

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

Answer to Question 1

Correct Answer: 3
Rationale 1: The cytochrome P460 enzyme system does not affect ability to cross the BBB. Lipid solubility of a drug determines the ability to cross the BBB.
Rationale 2: The drug will still be metabolized by the liver, not the kidneys.
Rationale 3: When one drug induces an enzyme system, it accelerates the metabolism of other drugs using the same isoenzyme substratein this case, the CYP3A4 system, which causes early inactivation of the drug.
Rationale 4: The drug will be metabolized faster and therefore excreted more quickly, not more slowly.
Global Rationale: When one drug induces an enzyme system, it accelerates the metabolism of other drugs using the same isoenzyme substratein this case, the CYP3A4 system, which causes early inactivation of the drug. The cytochrome P460 enzyme system does not affect ability to cross the BBB. Lipid solubility of a drug determines the ability to cross the BBB. The drug will still be metabolized by the liver, not the kidneys. The drug will be metabolized faster and therefore excreted more quickly, not more slowly.

Answer to Question 2

Correct Answer: 3
Rationale 1: Lopressor, not amiodarone, is more likely to be toxic, as it will take longer to be inactivated.
Rationale 2: It is not necessary to administer the drugs on an empty stomach; this will not alter the metabolism by the CYP enzyme system.
Rationale 3: The CYP enzyme system determines the speed at which most drugs are metabolized in the liver. When one drug inhibits the action of the same isoenzyme system, other drugs being metabolized by this same system might not be inactivated as quickly, leading to prolonged effects of the drug.
Rationale 4: It would not be necessary to administer the drugs two hours apart; this would not alter their metabolism by the CYP enzyme system.
Global Rationale: The CYP enzyme system determines the speed at which most drugs are metabolized in the liver. When one drug inhibits the action of the same isoenzyme system, other drugs being metabolized by this same system might not be inactivated as quickly, leading to prolonged effects of the drug. Lopressor, not amiodarone, is more likely to be toxic, as it will take longer to be inactivated. It is not necessary to administer the drugs on an empty stomach; this will not alter the metabolism by the CYP enzyme system. It would not be necessary to administer the drugs two hours apart; this would not alter their metabolism by the CYP enzyme system.