EXAM 5 - Metabolic Drug Interactions

Question 1

What are the two major types of drug interactions?

Answer 1

Enzyme inhibition
* reversible (most common)
* slowly reversible or irreversible

Enzyme induction
* transcriptional activation (more likely)
* protein (or mRNA) stabilization (less likely)

Question 1

What are the two major types of drug interactions?

Answer 1

Enzyme inhibition
* reversible (most common)
* slowly reversible or irreversible

Enzyme induction
* transcriptional activation (more likely)
* protein (or mRNA) stabilization (less likely)

Question 2

Explain why P450s are often involved in drug interactions.

Answer 2

P450s are often involved because so mamy drugs get metabolized by P450 enzymes.
* P450 enzymes can also be inhibited and induced by many other drugs.

Question 3

Explain why P450s are often involved in drug interactions.

Answer 3

P450s are often involved because so mamy drugs get metabolized by P450 enzymes.
* P450 enzymes can also be inhibited and induced by many other drugs.

Question 4

Describe the different effects of Rifampin and Troleandomycin on IV Midazolam.

Answer 4

Midazolam is an anesthetic metabolized by P4503A4 to form midazolam-OH.

Rifampin induces the effects of midazolam
* increases metabolism of midazolam which can result in uneffective dose bc it falls below the theraputic window

Troleandomycin inhibits the effects oif midazolam
* slows down the metabolism of midazolam –> concentration is too high –> fully anesthetized for longer than usual

Question 5

Explain the clinical significance of metabolic drug interactions.

Answer 5

• Changes the outcomes of drugs
• Predicting risk in specific patients

Question 6

What are the types of outcomes of metabolic drug interactions?

Answer 6

• no effect
• toxicity
• reduced therapeutic effect

Question 7

How do metabolic drug interactions predict risk in specific patients?

Answer 7

• patient related risk factors - pharmacogenetics, disease, habits, age
• dose - most DIs are related but not all (e.g. potent inhibitors)
• route of administration
• duration of administration - long half-life drugs are less effected
• sequence of administration - induction usually takes longer to occur than inhibition

Question 8

What are some ways pharmacists can manage drug interactions?

Answer 8

• identification of patients - computerized screening
• actions to reduce risk of adverse drug interactions
• computerized prevention of adverse interactions

Question 9

What are actions to reduce risk of adverses drug interactions?

Answer 9

a. Use of alternative noninteracting medications. Almost always
possible to do this
b. Adjust the dose based off response, rather than prophylactically
c. Adjust dosing times
d. Monitor for altered response