Drug Interactions

Question 1

Ketoconazole is a (inhibitor/inducer) of the P-gp?

Answer 1

Inhibitor

Question 2

What types of drugs generally induce CYP450 enzymes?

Answer 2

Anti-seizure, barbituates, herbals, alcohol, cigarettes

Question 3

Erythromycin is a (inhibitor/inducer) of the P-gp?

Answer 3

Inhibitor

Question 4

Sulfonamide competes with Warfarin for albumin binding. What effect with this have on the effects of Warfarin?

Answer 4

Under normal situations, only a small percentage of Warfarin is unbound. If sulfonamide competes for binding, the percentage of unbound Warfarin will increase and dramatically increase its effects.

Question 5

Rifampin is a (inhibitor/inducer) of the P-gp?

Answer 5

Inducer

Question 6

What types of drugs generally inhibit CYP450 enzymes?

Answer 6

Acid reducers, antibiotics, antifungals, HIV medications, Tb medications, grapefruit juice

Question 7

Interactions with what types of drugs (5) can be very clinically significant?

Answer 7

Drugs with low TI, drugs regulating bodily functions, drugs that are highly protein-bound, zero-order drugs, and drugs with poorly-defined therapeutics

Question 8

Inhibition of CYP450 enzymes will have what effect on Cp?

Answer 8

Increase Cp since CYP450 enzymes metabolize the drug for excretion

Question 9

A patient travels to Florida for the summer and is excited to drink grapefruit juice, their favorite juice. They present to the ER displaying symptoms associated with a toxic dose of their maintenance medication. The patient states they are taking the medication as prescribed. Should the ER Attending believe them?

Answer 9

Yes, grapefruit juice inhibits the P-glycoprotein causing less of the drug to be removed from the cell and potentially leading to toxic levels

Question 10

A patient is diagnosed with strep pyogenes infection and is prescribed a tetracycline. The physician instructs the patient not to consume dairy within several hours of taking the antibiotic. Why is this?

Answer 10

Ions in milk and dairy products chelate with tetracyclines and form complexes that cannot be absorbed. This decreases the effectiveness of the drug

Question 11

A drug is known to induce P-gp function. What effect will this have on the absorption of a therapeutic drug?

Answer 11

Absorption of the drug will decrease since the P-gp was induced and is now removing substances more rapidly

Question 12

Verapamil is a (inhibitor/inducer) of the P-gp?

Answer 12

Inhibitor

Question 13

What are the consequences of drug interactions?

Answer 13

Change in Cp, altered therapeutic effects, altered ADRs

Question 14

What is the mechanism and effect of MOA inhibitors?

Answer 14

MOA inhibitors ihibit the MAO, causing an increase in plasma tyramine. Tyramine stimulates catecholamine release

Question 15

What is the effect of alcohol consumption on CYP450 enzymes?

Answer 15

Acute heavy consumption inhibits CYP450, however, chronic heavy consumption induces CYP450

Question 16

What is the most significant drug interaction that alters Cp?

Answer 16

Metabolism interactions via enzyme inhibition or induction

Question 17

St. John’s Wort is a (inhibitor/inducer) of the P-gp?

Answer 17

Inducer

Question 18

How long do inhibition and induction of CYP450 enzymes take?

Answer 18

Inhibitors - Occurs quickly
Inducers - Occurs slowly over several weeks

Question 19

What protein serves as a transmembrane efflux transporter that protects the cell from harmful substances?

Answer 19

P-glycoprotein (P-gp)

Question 20

What is the difference between a drug interaction and drug incompatibility?

Answer 20

A drug interaction occurs in vivo and occurs when a drug modifies the action of another.

An incompatibility occurs in vitro and it is caused by an interaction between the drugs that may create a precipitate or other reaction.