MTM Pharmacotherapy Review & Drug Interactions 4

Question 1

Which drug is a substrate of CYP2D6 and may accumulate to toxic levels in 'poor metabolizers' of this enzyme?

Accepted Answer

Codeine

Answer

Codeine is converted to its active analgesic form (morphine) by CYP2D6; poor metabolizers accumulate codeine with little analgesia, while ultra-rapid metabolizers risk morphine toxicity.

Question 2

A patient taking simvastatin 80 mg is prescribed amlodipine. What adjustment is recommended?

Accepted Answer

Reduce simvastatin to no more than 20 mg/day due to CYP3A4 inhibition

Answer

Amlodipine is a weak CYP3A4 inhibitor; simvastatin 80 mg is already restricted due to myopathy risk, and the FDA recommends limiting simvastatin to 20 mg/day when co-administered with amlodipine.

Question 3

What is the mechanism of action of direct oral anticoagulants (DOACs) such as rivaroxaban?

Accepted Answer

Directly inhibit activated Factor Xa, preventing thrombin generation

Answer

Rivaroxaban is a direct Factor Xa inhibitor that blocks the conversion of prothrombin to thrombin without requiring antithrombin as a cofactor.

Question 4

Which medication requires therapeutic drug monitoring due to its narrow therapeutic index and non-linear (Michaelis-Menten) pharmacokinetics?

Accepted Answer

Phenytoin

Answer

Phenytoin exhibits saturable (zero-order at therapeutic concentrations) Michaelis-Menten kinetics, causing small dose increases to produce disproportionately large plasma level elevations.

Question 5

A diabetic patient on glipizide starts a fluoroquinolone antibiotic. What glucose-related adverse effect is possible?

Accepted Answer

Both hypoglycemia and hyperglycemia, depending on the specific fluoroquinolone

Answer

Fluoroquinolones can cause both hypoglycemia (by stimulating insulin secretion, especially gatifloxacin/moxifloxacin) and hyperglycemia by interfering with pancreatic beta-cell function.

(MTM) Medication Therapy Management Board Certification Practice Test

(MTM) Medication Therapy Management Board Certification Practice Test

MTM Pharmacotherapy Review & Drug Interactions 4